Engine fires, runs, then quits immediately

[82DMC12]

A couple weeks ago I blew one of the upper water pump hoses (the one that connects the pump to the passenger side head). It was about 15 years old, looked fine, pliable, but on inspection during removal, it had a crack on the inside. So, I decided it was time to go into the valley once again for a freshen-up and to replace all the coolant hoses on the engine. Everything went well and I did the following:



Removed ignition distributor to replace the o-ring on the shaft (oily residue around the distributor) and new impulse coil. First time taking the distributor apart but it went fine and I was sure to mark the timing nut and the rotor position - such that when I dropped it in, the rotor turned and hit my mark. I think it's fine? Also replaced cap (DMCH) and rotor (Bosch from Rock Auto) as well as new plug wires (DMCH)
Checked plugs which I installed this summer to make sure they look good - all look perfect
Machined the Y-pipe surface
Removed all three sensors from the Y-pipe for cleaning, the 3-way switch broke so I put a new one in (DMCH)
Updated the heater pipe to the DPI version (no more metal snake)
Replaced all vacuum lines
Routed engine harness under the air meter
Replaced all O-rings and gaskets to get into the valley including pipe of agony o-ring and FD o-ring
New belts
Thin coating of anti-seize on every screw, new washers for everything
Replaced PPR o-rings with D-go kit


Got it all back together no issues last night and tried to start it - it will turn over, fire, start, but then quit right away. Prior to this work I had no starting or running issues so it's something I have done this weekend.... See the video below.

My questions/thoughts:


I checked fuel pressure with my K-Jet gauge and my primary and control pressures are correct, rest pressure is fine but I do hear the accumulator clanking sometimes after turning off the fuel pump. Don't really remember that before. I have not tried to check pressure while the car is starting and trying to run.
I have not checked timing yet - I haven't done this in YEARS so as a refresher, is it OK to check timing with the fuel pump off and having a friend turn the key so the engine and ignition is running for a few seconds while I use the light?
How far into the air meter should be the pipe of agony be sticking in? I can see it through the meter plate if I release the fuel pressure and push down on the plate - I will check this again but I know the pipe is in there, just might not be far enough somehow
Does it matter which wire goes to which terminal on the idle microswitch? It's possible I got the wires reversed but I don't think so. I have the ground on the bottom terminal and the power on the top terminal right now.
When I removed the brass pipe for the CSV from the intake manifold, for some reason there was a copper washer down in there (in the pit where the long screw threads into). It's not in the parts manual so I removed it thinking it can't serve any purpose like that. Was I mistaken?
Thinking back about everything, it's POSSIBLE I forgot to torque the spark plugs down. I know they are threaded in by hand using an extension but now I'm trying to remember if I hit them with the torque wrench.... I think this would create a bad enough compression problem where the engine can't run, right? I'm going to check this first when I get home after work.


Appreciate any other ideas based on the evidence provided!


https://youtu.be/ub1kBN1S7cY

[David T]

If it is shutting of as soon as you release the ignition switch from the START position, it could be one of two things. Either you are not getting ignition power in the run position or you are only starting and running on the CSV and as soon as that stops (and the fuel stops) the motor stops. To time the motor it has to be running. As long as you are close it should run well enough to time it. Check the wires to the ballast resistor, maybe you knocked one loose.

[82DMC12]

If it is shutting of as soon as you release the ignition switch from the START position, it could be one of two things. Either you are not getting ignition power in the run position or you are only starting and running on the CSV and as soon as that stops (and the fuel stops) the motor stops. To time the motor it has to be running. As long as you are close it should run well enough to time it. Check the wires to the ballast resistor, maybe you knocked one loose.

Yeah it cranks, starts, I let off the key, it sounds a bit rough, and immediately dies. Once when I tried it, it ran for a couple seconds before dying but I couldn't get it any gas to rev it up before it quit.

OK I'll check the ballast resistor and the coil spade wires again. I was also thinking about the CO screw - I did not touch it during this rebuild but I did separate the halves of the meter to clean it out and used carb cleaner to get all the residue out of the lever and such. Maybe I'm running on CSV only and I need to adjust the screw to get the injectors to open up.

Remind me again - best to get the injectors in jars, jump the RPM relay, turn the screw until they spray, then back off until they just barely stop with no drips? And then it should be pretty damn close and I can use my dwell meter to dial it in once it's running. Maybe when I replaced the o-rings on the PPR, that somehow messed up the balance in the distributor. Or maybe I fixed a minor vacuum leak and that also messed up the balance.

[82DMC12]

Here's a picture prior to adding the fuel injection so you can see what I'm working with. Everything is pretty clean and it's not bad to poke around.

67798

[82DMC12]

By the way, prior to buttoning everything up on the engine, after I installed the FD and reconnected the feed and return lines, I had all the injectors out and I jumped the RPM relay to pressurize everything. I wanted to confirm I had no drippage or leaks, and sure everything was bone dry. I didn't put them in jars or press on the plate because I had actually recently done that this summer so I assumed everything was going to be OK putting the injectors back into the engine.

Is it safe to assume, based on the video, that the ignition distributor is at least CLOSE to correct since it actually does start for a moment before dying? There are a lot of variables there and it was my first time pulling the dizzy out and taking it apart. But there are only three or parts and hard to put together incorrectly if you paid attention during disassembly. I checked the impulse coil with my meter and resting still it was around 600 ohm, and it changed as I spun the shaft. Used a vacuum pump to check the vacuum advance and that's working fine too. I know the cap is oriented correctly and it's snapped into place in the alignment tab. The electrical connection to it is plugged back in and tucked into the firewall grommet.

[Helirich]

If the ballest resistor is un wired, you will not get it to fire at all. I’ve never timed an engine with a light that doesn’t run. (It should run some if your close). I’ve not heard of adjusting the mixture that way. (Doesn’t mean you can’t) I’m curious to hear what the others say.

Edit, I just watched the video. I think the timing is close.

[82DMC12]

If the ballest resistor is un wired, you will not get it to fire at all. I’ve never timed an engine with a light that doesn’t run. (It should run some if your close). I’ve not heard of adjusting the mixture that way. (Doesn’t mean you can’t) I’m curious to hear what the others say.

Edit, I just watched the video. I think the timing is close.

That mixture method I described is a way to get the mixture close, in the ball park, so the car will at least run enough so you can get a dwell on it and set properly. It's how you set it up if you're starting from scratch or someone else F'd it all up. Makes sense since you know the injectors should not be firing or dripping when the RPM relay is jumped or it would flood the engine. But they have to be ready to spray as soon as the meter plate gets sucked downward. So a slight tap on the plate while the system is under pressure should make them spray.

[Bitsyncmaster]

Your problem sounds like a large vacuum leak. Check that you have all your hoses connected and check the pipe of agony.

[AugustneverEnds]

+1 vacuum leak

Somehow is the plug for the CO adjustment not there? A garage forgot to replace mine and it had symptoms like yours. I swore I was going to need a FD and/or WUR rebuild until I covered the hole and it was back to its normal happy self.

[82DMC12]

+1 vacuum leak

Somehow is the plug for the CO adjustment not there? A garage forgot to replace mine and it had symptoms like yours. I swore I was going to need a FD and/or WUR rebuild until I covered the hole and it was back to its normal happy self.

I'm quite sure the CO plug is there, but I will double check when I get home. If it's vacuum, I'm leaning towards the pipe of agony got pulled out partly when hooking up the idle motor.

I'll be back on tonight, hopefully, after I get a chance to check some of these ideas, with an update.

[Bitsyncmaster]

I'm quite sure the CO plug is there, but I will double check when I get home. If it's vacuum, I'm leaning towards the pipe of agony got pulled out partly when hooking up the idle motor.

I'll be back on tonight, hopefully, after I get a chance to check some of these ideas, with an update.

The mixture plug is not a very large leak. You can shine a light down around the pipe in the dark and press the air plate down and look for light inside the FD.

[AugustneverEnds]

The mixture plug is not a very large leak. You can shine a light down around the pipe in the dark and press the air plate down and look for light inside the FD.

My car must be very partial to its mixture plug, it ran like crap, backfired a little, and refused to start or restart without starting fluid before I thought to check it and cover it.

[Bitsyncmaster]

My car must be very partial to its mixture plug, it ran like crap, backfired a little, and refused to start or restart without starting fluid before I thought to check it and cover it.

Mine has very little affect even when measuring dwell. I do cover it to finalize the dwell adjustment.

[Ron]

A couple weeks ago I blew one of the upper water pump hoses (the one that connects the pump to the passenger side head). It was about 15 years old, looked fine, pliable, but on inspection during removal, it had a crack on the inside. So, I decided it was time to go into the valley once again for a freshen-up and to replace all the coolant hoses on the engine. Everything went well and I did the following:



Removed ignition distributor to replace the o-ring on the shaft (oily residue around the distributor) and new impulse coil. First time taking the distributor apart but it went fine and I was sure to mark the timing nut and the rotor position - such that when I dropped it in, the rotor turned and hit my mark. I think it's fine? Also replaced cap (DMCH) and rotor (Bosch from Rock Auto) as well as new plug wires (DMCH)
Checked plugs which I installed this summer to make sure they look good - all look perfect
Machined the Y-pipe surface
Removed all three sensors from the Y-pipe for cleaning, the 3-way switch broke so I put a new one in (DMCH)
Updated the heater pipe to the DPI version (no more metal snake)
Replaced all vacuum lines
Routed engine harness under the air meter
Replaced all O-rings and gaskets to get into the valley including pipe of agony o-ring and FD o-ring
New belts
Thin coating of anti-seize on every screw, new washers for everything
Replaced PPR o-rings with D-go kit


Got it all back together no issues last night and tried to start it - it will turn over, fire, start, but then quit right away. Prior to this work I had no starting or running issues so it's something I have done this weekend.... See the video below.

My questions/thoughts:


I checked fuel pressure with my K-Jet gauge and my primary and control pressures are correct, rest pressure is fine but I do hear the accumulator clanking sometimes after turning off the fuel pump. Don't really remember that before. I have not tried to check pressure while the car is starting and trying to run.
I have not checked timing yet - I haven't done this in YEARS so as a refresher, is it OK to check timing with the fuel pump off and having a friend turn the key so the engine and ignition is running for a few seconds while I use the light?
How far into the air meter should be the pipe of agony be sticking in? I can see it through the meter plate if I release the fuel pressure and push down on the plate - I will check this again but I know the pipe is in there, just might not be far enough somehow
Does it matter which wire goes to which terminal on the idle microswitch? It's possible I got the wires reversed but I don't think so. I have the ground on the bottom terminal and the power on the top terminal right now.
When I removed the brass pipe for the CSV from the intake manifold, for some reason there was a copper washer down in there (in the pit where the long screw threads into). It's not in the parts manual so I removed it thinking it can't serve any purpose like that. Was I mistaken?
Thinking back about everything, it's POSSIBLE I forgot to torque the spark plugs down. I know they are threaded in by hand using an extension but now I'm trying to remember if I hit them with the torque wrench.... I think this would create a bad enough compression problem where the engine can't run, right? I'm going to check this first when I get home after work.


Appreciate any other ideas based on the evidence provided!


https://youtu.be/ub1kBN1S7cY
1. Maybe see if it will stay running with short spurts of staring fluid.
2. In the vid, the tach appears to show ignition while it is dying (see #1 above ;-).
3. If you can see the entire opening, it's probably not the problem.
(It passes through an o-ring and it's keeper. )
4. It doesn't matter which wire goes to which terminal on the ISM micro switch.
5. The long bolt goes through a copper washer, the bypass pipe, and then an o-ring.
(Check this out (https://store.delorean.com/parts/fuel-emissions/2-2-1-cold-start-valve-thermotime-switch.html)).
6. All else ok, if the plugs are hand tight, it would run. (Not good for the threads, of course.)

[82DMC12]

Ron, the CSV washer I was talking about was a copper washer that was laying flat on the bottom of the intake under the brass pipe and the long screw went through it. Made no sense and didn't see it in the parts book.



Well I haven't learned too much yet but I did eliminate a few things.

1. I finagled the Pipe of Agony and the associated elbow hoses and got it to go another centimeter into the air meter and also confirmed the o-ring is still in place. I think we can conclude there are no vacuum leaks between the CVS to the lower air meter.

2. Confirmed the large vacuum line is going to the passenger side rear intake (hose clamped tight) and the manifold vacuum to the three way switch on the Y-pipe is also plugged in.

3. Rechecked all vacuum routing - OK

4. Removed and reinserted all wires to the ballast resistor and the ignition coil - Seems OK

5. Spark plugs were indeed torqued to 14 ft lbs - didn't forget! Checked plug wires - OK

Not much luck. It still starts after three or cranks but then dies right away just like in the video. However now I can give it a bit of gas pedal once it starts and I can get it to rev with each press of the pedal, but it sounds weak, and of course dies as soon as I let off the gas.

I'm trying to eliminate vacuum leaks as a cause so I'm thinking about the places it could leak that I touched.

Pipe of agony - checked and should be OK now
W-pipe paper gaskets - checked
W-pipe o-rings - now I'm missing the "Back Up Rings" 102282 and I think I've always been without them. I have the o-rings on the W-pipe and I tried to double-up the rings like suggested on DeLorean.com but I couldn't get it to go together that way. I ordered the back up rings from DPI and will put them in as soon as I get them.
Air meter halves gasket - replaced this and used red spray-tack gasket sealant, tightened all cap screws
Didn't mess with the meter plate or the CO screw but I did clean everything in there with carb cleaner. I did look at the plate with a light behind it and it looked perfectly even all around.
Throttle spacer - cleaned with silicone spray, it's not damaged
Cleaned throttle with carb cleaner, worked the decel springs and made sure they were seated properly before installing the throttle.
Confirmed the throttle is indeed closed
Two manifold ports on the rear upper parts of the intake manifold - hoses are on
Six intake o-rings - replaced, didn't use any grease, put them in dry. Carefully added the intake manifold over it and tightened the four manifold bolts in criss cross. Looking at the head-to-manifold mating area it appears even and flush. I did lightly clean the manifold mate surface with a pneumatic wire wheel.


Not quite sure where to go next! I'm afraid I may have to tear back down to the valley again and check everything from the bottom up....

[DMC-Ron]

4. Removed and reinserted all wires to the ballast resistor and the ignition coil - Seems OK


I know your checked the ballast resistor, but you might do a very simple test to insure the white with yellow (W/Y) wire headed to the coil is getting +12 with the ignition switch in the run position. The car can start from the cranking power provided to the ballast resistor then drop out when the switch returns to the run position.

Ron

[MrChocky]

A the risk of saying something completely obvious, and I didn't see this mentioned, have you checked you TTS plug? On mine, one
of the pins backed out, and I had cold start symptoms that sound a lot like what you're having.

[82DMC12]

I know your checked the ballast resistor, but you might do a very simple test to insure the white with yellow (W/Y) wire headed to the coil is getting +12 with the ignition switch in the run position. The car can start from the cranking power provided to the ballast resistor then drop out when the switch returns to the run position.

Ron

Hi Ron,

In RUN, I am getting +12V to white/yellow at the coil but only if I remove the wire from the dual spade (which is shared with a noise suppressor yellow wire) and test it by itself. But then, if I plug the white/yellow wire back into the coil (key still in RUN), and I measure the coil terminal that I just plugged it into, I am getting 5.8V. Does that sound right?

I reconfirmed all the wires on the ballast resistor are connected tightly and also removed and reinserted the resistor grid relay.

[82DMC12]

A the risk of saying something completely obvious, and I didn't see this mentioned, have you checked you TTS plug? On mine, one
of the pins backed out, and I had cold start symptoms that sound a lot like what you're having.

No bad ideas here. I did remove the plug and inspected it, the pins are both in the correct position and it feels secure when I reinstall the plug.

[82DMC12]

So I was just reading this thread -

http://dmctalk.org/showthread.php?1277-Ignition-coil-questions/page2

In it, Dave M says white/yellow should go to + terminal on Accel coils. Mine has been wired up opposite that for probably 15 years. Is that a thing? I've never had ignition problems until now so I'm not sure I should swap it....

67807

[David T]

If you can keep it running but it runs badly, either you have bad, dirty injectors or the mixture is way off. Check the flow patterns on the injectors and if they look OK tweak the mixture screw a little richer.

[Ron]

Ron, the CSV washer I was talking about was a copper washer that was laying flat on the bottom of the intake under the brass pipe and the long screw went through it. Made no sense and didn't see it in the parts book.Maybe I'm not following you... There needs to be a seal there. (I've seen copper and rubber there.) Its #9 in the link I gave you above.


Hi Ron,

In RUN, I am getting +12V to white/yellow at the coil but only if I remove the wire from the dual spade (which is shared with a noise suppressor yellow wire) and test it by itself. But then, if I plug the white/yellow wire back into the coil (key still in RUN), and I measure the coil terminal that I just plugged it into, I am getting 5.8V. Does that sound right?
In RUN, power (12V) has to go through 2 resistors in the block. While cranking, it goes through one resistor. So, there shouldn't be 12V on the white/yellow at any time.
67808

So I was just reading this thread -

http://dmctalk.org/showthread.php?1277-Ignition-coil-questions/page2

In it, Dave M says white/yellow should go to + terminal on Accel coils. Mine has been wired up opposite that for probably 15 years. Is that a thing? I've never had ignition problems until now so I'm not sure I should swap it....
Swap it!

[Helirich]

If you can keep it running but it runs badly, either you have bad, dirty injectors or the mixture is way off. Check the flow patterns on the injectors and if they look OK tweak the mixture screw a little richer.

This would be my guess. It doesnt take much on that screw to make it run like crap.

[82DMC12]

Hi Ron,

OK I'll try to explain better.

For the CSV, I have, in order, Bolt head, washer, brass pipe, o-ring, manifold. Just like it shows in the parts diagram https://store.delorean.com/parts/fuel-emissions/2-2-1-cold-start-valve-thermotime-switch.html

What I found on disassembly, laying in the hole in the manifold that the CSV sprays into, in the casing, there was a copper washer on the floor of the port in there, which the screw ran through and then threaded into the manifold. But that makes no sense to me because the bolt does not need to be sealed there and there is no force downward onto the washer. So I think it was someone's mistake in the past. The washer is not found in the parts book for either the link above or the Induction system page. Does that make better sense?

Regarding the ignition coil, I will definitely do some continuity checks tonight but here is what I have -


+ side of the coil has a white (maybe it's white/slate) wire going to it and that's it
- side of the coil has a white/yellow wire going to it as well as a noise suppressor mounted on the firewall. These two wires are connected on a piggy back connector and then pushed onto the coil spade.
If I remove the white/yellow wire from the piggyback terminal and test it alone with a meter (stick a probe into the wire connector) I am getting 12V with the key in RUN position (red probe on wire, black probe on engine)
If I put the wire back onto the terminal and then test the terminal itself, I get just under 6V with the key in the RUN position (red probe on terminal, black probe on engine)


How can the voltage drop just because the wire is plugged into the coil? I have not tried to check the voltage during cranking yet.

I'm trying to read your diagram. I'm using this one but it doesn't have the relay in it.

67809

Looking at this diagram, all the wires look correct with the exception of my coil terminals are apparently reversed and I have two white wires going to the top right ballast resistor terminal.

Looking at your diagram, is the flag-looking thing on the bottom supposed to be the coil? If so, it seems to show UY going to one side of the coil, and a WY+ W going to the other side? Am I reading this right?

Could I have a problem with the ballast resistor relay? I have a number of relays laying around if I know what type I can swap it with.

A lot of people think these Super Stock coils are trouble. How can I test it with my meter?

Maybe I should switch back to a standard Bosch coil like this one
https://www.rockauto.com/en/moreinfo.php?pk=282426&cc=1312343&pt=7060&jsn=302

Additional photos for reference -

67810
67811

[82DMC12]

This would be my guess. It doesnt take much on that screw to make it run like crap.

I am going to get some more mason jars and go through this process again once I rule out ignition coil/ ballast

[Helirich]

I am going to get some more mason jars and go through this process again once I rule out ignition coil/ ballast

The mason jars test is to check balance across the injectors. It’s a good idea and I need to do it, but in your case, just pulling one injector and making sure it is spraying the minute you push the plate down might be the answer.

[82DMC12]

The mason jars test is to check balance across the injectors. It’s a good idea and I need to do it, but in your case, just pulling one injector and making sure it is spraying the minute you push the plate down might be the answer.


Good point. I literally just checked flow with six jars in like, September, so I'm sure it all has to be good in terms of pattern and volume. Even if it wasn't, it would still run, just crappy. I can't even get it to idle right now.

Am I correct in that I can get a baseline CO by pulling an injector, placing it in a jar, jump the RPM relay, then check for spray. Turn the CO screw clockwise (richer) until I get a spray, then back off until it just stops? I already know I'm not flooding because I had all six injectors out when reinstalling the whole fuel injection and I did do a quick RPM relay jump to make sure I was leak-free before putting the injectors back into the ports.

[Ron]

Hi Ron,

OK I'll try to explain better.

For the CSV, I have, in order, Bolt head, washer, brass pipe, o-ring, manifold. Just like it shows in the parts diagram https://store.delorean.com/parts/fuel-emissions/2-2-1-cold-start-valve-thermotime-switch.html

What I found on disassembly, laying in the hole in the manifold that the CSV sprays into, in the casing, there was a copper washer on the floor of the port in there, which the screw ran through and then threaded into the manifold. But that makes no sense to me because the bolt does not need to be sealed there and there is no force downward onto the washer. So I think it was someone's mistake in the past. The washer is not found in the parts book for either the link above or the Induction system page. Does that make better sense?

Regarding the ignition coil, I will definitely do some continuity checks tonight but here is what I have -


+ side of the coil has a white (maybe it's white/slate) wire going to it and that's it
- side of the coil has a white/yellow wire going to it as well as a noise suppressor mounted on the firewall. These two wires are connected on a piggy back connector and then pushed onto the coil spade.
If I remove the white/yellow wire from the piggyback terminal and test it alone with a meter (stick a probe into the wire connector) I am getting 12V with the key in RUN position (red probe on wire, black probe on engine)
If I put the wire back onto the terminal and then test the terminal itself, I get just under 6V with the key in the RUN position (red probe on terminal, black probe on engine)


How can the voltage drop just because the wire is plugged into the coil? I have not tried to check the voltage during cranking yet.

I'm trying to read your diagram. I'm using this one but it doesn't have the relay in it.



Looking at this diagram, all the wires look correct with the exception of my coil terminals are apparently reversed and I have two white wires going to the top right ballast resistor terminal.

Looking at your diagram, is the flag-looking thing on the bottom supposed to be the coil? If so, it seems to show UY going to one side of the coil, and a WY+ W going to the other side? Am I reading this right?

Could I have a problem with the ballast resistor relay? I have a number of relays laying around if I know what type I can swap it with.

A lot of people think these Super Stock coils are trouble. How can I test it with my meter?

Maybe I should switch back to a standard Bosch coil like this one
https://www.rockauto.com/en/moreinfo.php?pk=282426&cc=1312343&pt=7060&jsn=302



Yes, clearer...I was not getting you had an o-ring AND and the "extra" copper washer between the pipe and manifold.

The flag looking thing is the wire harness (each wire is labeled where it goes to...).

The voltage can (will) drop when the wire is connected to the coil because the coil is a load (resistor)...
The White wire from the aux. solenoid brings 12v to the resistor block. In RUN it goes through 2 resistors, reducing the voltage "a lot". In START, the relay bypasses one resistor, reducing the voltage "a little". (This is just for hotter spark during cranking...and to keep the coil from overheating etc.)
You do not want anything but the white/slate wire connected to the (-) side of the coil, because anything else will interfere with the ignition signal.

From manual, with relay:
67812

[82DMC12]

Yes, clearer...I was not getting you had an o-ring AND and the "extra" copper washer between the pipe and manifold.

The flag looking thing is the wire harness (each wire is labeled where it goes to...).

The voltage can (will) drop when the wire is connected to the coil because the coil is a load (resistor)...
The White wire from the aux. solenoid brings 12v to the resistor block. In RUN it goes through 2 resistors, reducing the voltage "a lot". In START, the relay bypasses one resistor, reducing the voltage "a little". (This is just for hotter spark during cranking...and to keep the coil from overheating etc.)
You do not want anything but the white/slate wire connected to the (-) side of the coil, because anything else will interfere with the ignition signal.

From manual, with relay:
67812

OK so it sounds like my meter readings are normal then. I think the best thing to do next is to try to test the coil to make sure it's not burned out or something (how do I do that?), reverse the wiring on it so it's correct, and then do a CO check.

[Ron]

OK so it sounds like my meter readings are normal then. I think the best thing to do next is to try to test the coil to make sure it's not burned out or something (how do I do that?), reverse the wiring on it so it's correct, and then do a CO check. ...except you shouldn't be showing 12V on the white/yellow wire, ever. You can put 12V on the coil (+) as a test, but don't leave it that way...

[Helirich]

Good point. I literally just checked flow with six jars in like, September, so I'm sure it all has to be good in terms of pattern and volume. Even if it wasn't, it would still run, just crappy. I can't even get it to idle right now.

Am I correct in that I can get a baseline CO by pulling an injector, placing it in a jar, jump the RPM relay, then check for spray. Turn the CO screw clockwise (richer) until I get a spray, then back off until it just stops? I already know I'm not flooding because I had all six injectors out when reinstalling the whole fuel injection and I did do a quick RPM relay jump to make sure I was leak-free before putting the injectors back into the ports.

That sounds logical. You could also leave it altogether and just turn it a 1/2 Turn rich and see if it starts. That will probably be too rich and run like crap. But if it runs, you know you found the issue. Then you could turn it 1/8 turn lean at a time till it runs somewhat good. Then you probably need a dwell meter unless you get real lucky. Just make sure you know where your starting point is in case you want to return to square one.

[82DMC12]

...except you shouldn't be showing 12V on the white/yellow wire, ever. You can put 12V on the coil (+) as a test, but don't leave it that way...

Ron, I'm quite confused now. Earlier you said

_____
I know your checked the ballast resistor, but you might do a very simple test to insure the white with yellow (W/Y) wire headed to the coil is getting +12 with the ignition switch in the run position. The car can start from the cranking power provided to the ballast resistor then drop out when the switch returns to the run position.
_____

But I am getting 12V on the white/yellow wire with the key in RUN (key turned two clicks forward) if I take the white/yellow wire off of the coil terminal. In the diagram, white-yellow comes directly from the lower ballast resistor. Maybe my resistor relay is stuck? I will check for 0.5 ohm on both resistors tonight.

Do I have this sorted out in my head now?!?

[Ron]

Hehe.. that wasn't me. Ron versus DMC-Ron.

I'm sure your wires are wrong (because of the capacitor being on the wrong side of the coil and you getting 12V on the white/yellow wire). I can't tell what colors the wires are from the pics to help better.

[82DMC12]

Hehe.. that wasn't me. Ron versus DMC-Ron.

I'm sure your wires are wrong (because of the capacitor being on the wrong side of the coil and you getting 12V on the white/yellow wire). I can't tell what colors the wires are from the pics to help better.

:bash: Damn it too many Ron's!

OK let me just start with switching those coil wires around, checking ohms on the resistors, and then we can go from there! If the resistor relay is just a regular relay like most of them in the relay compartment I have a couple spares I can swap it out with to see if that makes a difference. Maybe having these wires reversed for 15 years worked out OK but now something else like the relay or resistor has gone haywire and it's not going to work anymore.

[Ron]

lol!

Try removing all but the white/slate (- side) and a 12V jumper (+ side) on the coil.
This will eliminate the resistor block, relay, etc.

It takes some trial and error, but you can usually get one to idle/rev if you manually work the throttle spool and the air plate together...

[David T]

Very low voltage can also cause it to run badly. Make sure you have at least 12 volts.

[82DMC12]

Very low voltage can also cause it to run badly. Make sure you have at least 12 volts.

Yeah when I first got everything back together and plugged the battery in, my battery was low and needed a charge. I've had it on a trickle now for a couple days and it's fully topped up. Battery is less than a year old and when I tried to start it this morning, no improvement. I'm just going to leave the trickle on it whenever I'm not actively working on the car so I know it's always full until I get the engine running like it should. Obviously the battery will run down if I keep trying to start the car but not getting it to run.

[Azar]

Sounds to me your RPM relay losing signal after you finish cranking and motor is starving for fuel...

[82DMC12]

Hey guys, making some good progress here I think. I pulled my injectors out and put them in mason jars so I could double check volume and pattern. They all look good. While I was at it, I removed the fuel distributor just enough so I was 100% sure the o-ring was still in place and the metering pin is free. I also reached in and checked the roller to make sure it too was moving freely.

Next I started turning my CO screw clockwise to richen the mixture and to my shock I had to turn the thing about 2.5 times to get the injectors to crack open. I then played with it a bit so I could get the sweet spot where the injectors just barely stop dripping after leaning it out. You can kind of tell by the singing sound.

Still not believing this could be possible because I have not touched the screw in years, I hooked up my pressure gauge to reconfirm primary and control pressure. Primary pressure is the same as it's always been at 4.8 bar and control pressure is about 2 bar which makes sense for the ambient temperature in my garage. I know the primary pressure sounds a bit low but that's what it's always read on this gauge so maybe my gauge is not quite calibrated.

Anyway I'm leaving the gauge on for an hour or two so I can monitor rest pressure and make sure I'm not bleeding out.

I'm not one who likes mysteries. I certainly did not turn the screw, and it was a little bit stiff so there's no way that it turned on its own while handling the air meter. The only thing I can think of is I did replace the o-rings on the PPR but my pressures have not changed since doing so.

Can anyone think of a logical reason that would cause the CO to be off that severely after doing a valley dive? I don't really want to go through timing the engine and using the dwell meter if this is a bogus screw position because I'm overlooking something else that needs to be corrected first.

Sent from my Pixel 3a using Tapatalk

[Rich]

Can anyone think of a logical reason that would cause the CO to be off that severely after doing a valley dive? I don't really want to go through timing the engine and using the dwell meter if this is a bogus screw position because I'm overlooking something else that needs to be corrected first.


Yes, the most likely reason is that something in your VOD rebuild left your engine with a decent-size vacuum leak. That would lean out the mixture at any given CO screw setting.

Recommending you run a smoke test to verify/locate any vac leak(s). Ideally you can repair those and then adjust the mixture/CO screw closer to where it used to be. Smart of you to count the adjustment turns to get it running. And smart of you to notice and report that you had to richen the mixture.

So many potential leak points are in play in a VOD job...the Pipe of Agony and its seal, any of the o-rings, vac hoses and components they attach to, the idle speed motor and more.

[82DMC12]

Yes, the most likely reason is that something in your VOD rebuild left your engine with a decent-size vacuum leak. That would lean out the mixture at any given CO screw setting.

Recommending you run a smoke test to verify/locate any vac leak(s). Ideally you can repair those and then adjust the mixture/CO screw closer to where it used to be. Smart of you to count the adjustment turns to get it running. And smart of you to notice and report that you had to richen the mixture.

So many potential leak points are in play in a VOD job...the Pipe of Agony and its seal, any of the o-rings, vac hoses and components they attach to, the idle speed motor and more.But what would a vacuum leak have to do with the opening pressure of the injectors? The car was not running as I was setting the CO screw to see if I can get the injectors to start dripping or spraying. I had to turn it clockwise quite a bit in order to get the injectors to start singing. I can see a vacuum leak being a problem while adjusting the screw while the engine is running on a dwell meter, but not with just the RPM relay jumped. Know what I mean?

Sent from my Pixel 3a using Tapatalk

[82DMC12]

Update for tonight -

The car is now running! The CO is set roughly at this point as I have not put my dwell meter on it or checked any other engine settings besides timing. I just have it set so the injectors barely stopped dripping, and double-checked by tapping the plate a few times and letting the pressure return and check for drips again. That worked well enough so the car started on the first try. It sounded a bit rough so I put the timing light on and found it was probably around 20 deg instead of 13. Got that adjusted easily so I'm right on the mark and it sounds better now. I didn't run it long because I still need to bleed the cooling system after refilling it and I don't want to do that until I replace the coolant hoses under the fuel tank plate which I found started to leak a bit after I put a pressure tester on the expansion tank.

So, I'll get those in this weekend and then bleed the coolant, and then see what I find with the dwell meter. I'll probably put a new O2 sensor in too since I haven't done that in forever.

I also turned the Accel ignition coil around and swapped the terminals so I now have the wires on the correct posts, but amazingly that didn't seem to do much with the ignition. Weird!

I am out of town for work Thurs and Fri so I won't have much more to add until the weekend, but I'm still trying to understand how the CO got so far off. The initial injector crack setting can only be governed by primary and control fuel pressure. It must be related to the PPR o-ring replacement I did. Perhaps my CO was set LAST TIME with the old o-rings which were maybe not so good and tight?

[DMC-Ron]

...except you shouldn't be showing 12V on the white/yellow wire, ever. You can put 12V on the coil (+) as a test, but don't leave it that way...

Ron,
I think there should be + voltage on the W/Y wire. When cranking the power (+12) flows thru a single resistor, in run, the power flows thru both resistors. After going thru the resistors power goes thru the W/Y wire to the coil. If you pull the W/Y wire off the coil and measure, you should see +12 volts. If you measure connected to the coil the voltage will be lower because of the resistor drop and the coil load. I'm guessing 5 or 6 volts is about right.

Ron

67813

[Helirich]

Update for tonight -

The car is now running! The CO is set roughly at this point as I have not put my dwell meter on it or checked any other engine settings besides timing. I just have it set so the injectors barely stopped dripping, and double-checked by tapping the plate a few times and letting the pressure return and check for drips again. That worked well enough so the car started on the first try. It sounded a bit rough so I put the timing light on and found it was probably around 20 deg instead of 13. Got that adjusted easily so I'm right on the mark and it sounds better now. I didn't run it long because I still need to bleed the cooling system after refilling it and I don't want to do that until I replace the coolant hoses under the fuel tank plate which I found started to leak a bit after I put a pressure tester on the expansion tank.

So, I'll get those in this weekend and then bleed the coolant, and then see what I find with the dwell meter. I'll probably put a new O2 sensor in too since I haven't done that in forever.

I also turned the Accel ignition coil around and swapped the terminals so I now have the wires on the correct posts, but amazingly that didn't seem to do much with the ignition. Weird!

I am out of town for work Thurs and Fri so I won't have much more to add until the weekend, but I'm still trying to understand how the CO got so far off. The initial injector crack setting can only be governed by primary and control fuel pressure. It must be related to the PPR o-ring replacement I did. Perhaps my CO was set LAST TIME with the old o-rings which were maybe not so good and tight?

That’s good news. One thing that could have happened is the warm up regulator was not reducing control pressure enough. There are several reasons this can occur. That makes it harder for idle vacuum to pull the plate down. I know you said you checked this, but maybe it’s fine at rest and only occurs when running. If this is the problem, you might find it will be too rich after warm up.

[82DMC12]

That’s good news. One thing that could have happened is the warm up regulator was not reducing control pressure enough. There are several reasons this can occur. That makes it harder for idle vacuum to pull the plate down. I know you said you checked this, but maybe it’s fine at rest and only occurs when running. If this is the problem, you might find it will be too rich after warm up.


I'm trying to think about this logically. Anyone who thinks I am not describing this properly, feel free to chime in and have the discussion!

We know the metering pin in the FD is always riding on the roller connected to the "see-saw". The CO screw is able to lift the roller or drop the roller so that the metering pin is "higher" or "lower" in the FD when the air plate is at a neutral position. So, basically the CO screw sets the initial position of the pin within the FD. If we have the RPM relay jumped, we have a constant fuel pressure supplied to the FD and it's just waiting to be routed to the injectors. If the pressure is sufficient, the fuel will spray through the injectors because the opening pressure of the injectors is fixed. There should be zero fuel going to the injectors when the metering plate is in a rest/neutral position, or else the engine would flood while jumping the RPM relay.

If the initial setting of the CO screw is too lean (CCW), the pin will require more travel (air plate pushed down further) to get the fuel to move to the upper half of the FD and then to the injectors. If the initial setting of the CO screw is too rich (CW) the injectors will be leaking into the cylinders.

The only thing that can change the initial CO setting is a change in primary pressure, a change in control pressure, or a change in the physical location of the FD (such as using too thick of an o-ring underneath it).

I did change the O-ring with a new one from DMCMW and I did replace the o-rings on the PPR which could have affected the primary pressure. Maybe between both of those changes, it affected the relative spacial relationship of the metering pin to the slits in the FD.

Since all this is done without the engine running, vacuum cannot be an influence in the initial setting (RPM relay jumped).

Now that I think about it, I don't believe control pressure can influence this setting either, since we do not have any downward force on the meter plate. The control pressure simply provides resistance to the plate so that it requires more air flow to move the pin during a warm condition.

What do you all think? This was written on my first mug of coffee.

[Helirich]

I agree with what youÂ’re saying if the fuel is supposed to spray the minute the plate goes down. IÂ’m not sure if this is true. I very well could be wrong, but IÂ’ve not read at what point the fuel should spray.

For example, let’s say when the motor is idling normally, the plate is down 1/2”. Then I suppose if the fuel started spraying when the plate is down 3/8”, it could run fine. You turn the key, the engine vacuum sucks it down 3/8”, it starts and sucks down further to the 1/2” mark. If you give it throttle, it sucks down further yet increasing fuel for power.

So if your WUR was not reducing control pressure enough, it would be harder for the vacuum to suck the plate down. If idle vacuum could only suck it down 1/4”, it would stall right after the cold start fuel ended. In this scenario, if you adjusted the mixture screw so that a 1/4” of plate travel gives it some fuel, it will probably run. But of course, when you give it more throttle, it maybe too rich.

I completely made up these numbers. I donÂ’t have any idea how far the plate moves at idle. IÂ’m just giving you my logic here. And a possible reason the mixture screw would have to be adjusted that far because of a bad WUR.

Is there a reference that says the fuel must spray with in the first 1/8” of travel?

Edit, please dismiss the stupid “A’s” in my post. My stupid IPad does that all the time on this site. I don’t know why.

[Rich]

But what would a vacuum leak have to do with the opening pressure of the injectors? The car was not running as I was setting the CO screw to see if I can get the injectors to start dripping or spraying. I had to turn it clockwise quite a bit in order to get the injectors to start singing. I can see a vacuum leak being a problem while adjusting the screw while the engine is running on a dwell meter, but not with just the RPM relay jumped. Know what I mean?

Got it. You're right.

Thought you were by now chasing a mixture problem while engine ran, not the original non-start and injector spray issue. Just a misread on my part.

Good to hear you got it running today and are back where you expect the CO setting to be.

[82DMC12]

I agree with what youÂ’re saying if the fuel is supposed to spray the minute the plate goes down. IÂ’m not sure if this is true. I very well could be wrong, but IÂ’ve not read at what point the fuel should spray.

For example, let’s say when the motor is idling normally, the plate is down 1/2”. Then I suppose if the fuel started spraying when the plate is down 3/8”, it could run fine. You turn the key, the engine vacuum sucks it down 3/8”, it starts and sucks down further to the 1/2” mark. If you give it throttle, it sucks down further yet increasing fuel for power.

So if your WUR was not reducing control pressure enough, it would be harder for the vacuum to suck the plate down. If idle vacuum could only suck it down 1/4”, it would stall right after the cold start fuel ended. In this scenario, if you adjusted the mixture screw so that a 1/4” of plate travel gives it some fuel, it will probably run. But of course, when you give it more throttle, it maybe too rich.

I completely made up these numbers. I donÂ’t have any idea how far the plate moves at idle. IÂ’m just giving you my logic here. And a possible reason the mixture screw would have to be adjusted that far because of a bad WUR.

Is there a reference that says the fuel must spray with in the first 1/8” of travel?

Edit, please dismiss the stupid “A’s” in my post. My stupid IPad does that all the time on this site. I don’t know why.

All good conversation here. I'm not sure there's a specification for how far down the plate should go before fuel sprays but my guess is basically immediately because once the CSV stops firing, you need fuel to run, and the vacuum, as you said, is pulling the plate downward. So any downward pull has to result in fuel spray.

I have some Bosch books at home so I'll see if it says anything about this measurement.

My understanding is that from a practical standpoint, after doing a dwell fine-tune, that the CO screw will end up being slightly lean compared to the rough "crack setting" I have done so far.

[Ron]

Ron,
I think there should be + voltage on the W/Y wire.
...

RonUggg...I don't know what I was thinking about, with it removed. ...It would obviously read the battery voltage with the meter itself being in series.

Thanks!
(It's Ron's fault ;-)

[Bitsyncmaster]

Here is what you should expect for coil voltage on our DeLorean.

Assuming you have the stock blue coil, 12.5 volt battery voltage, engine not running, stock wiring and stock ignition ECU, stock resistor setup.

Primary coil resistance is 0.40 ohms at room temp. Ignition ECU drives negative coil to 0.7 volts. So not counting harness resistance the coil voltage will be 4.07 volts (measured from the + and - coil terminals). This is probably the highest voltage you should expect since the harness wire is dropping voltage not accounted for with that calculation.

FYI:
The copper (in the coil and in the car harness) resistance increases 0.393 % per deg. C. My testing was done at room temp (70 deg.F or 20 deg.C).

Normal designed coil current is 5 to 7 amps on most all older cars.

[JtBosman1979]

So this thread is great, and exactly what I was looking for! Thank you to all who replied and the original posted this, because I recently did a VOD rebuild and now I am having the same problem, car starts, just dies right away. Can someone please tell me what the "CO" screw is and where to find it? Am sorry, am new, but I have worked a few cars in my day, but by no means a mechanic. So sorry if this is a simple question. I also replaced all my vacuum lines with a kit from DeLoreanGo, and also replaced all the O-rings, so am guessing I am having a mixture issue too.

Thank you for all your help, and thank you for posting this thread. I was pretty sad tonight to find it wouldn't start after working so hard on it.

Josh

[Ron]

https://dmctalk.org/showthread.php?12909-How-To-Set-CO-Dwell

[Rich]

......I recently did a VOD rebuild and now I am having the same problem, car starts, just dies right away. Can someone please tell me what the "CO" screw is and where to find it?

Ron showed you where the CO screw is.

Two more things just in case:

1. Looking for clarity on the symptom: Does at all for a few seconds or longer after you stop cranking it or does it die immediately when you stop cranking?

2. As you know, a VOD job includes removal and replacement of the throttle linkage and the idle speed switch/motor/wires. Be sure everything is set up and connected the way it was.