Fuel Problem

[jafo2k]

Hi all, well I got a fuel problem and just can't find the problem. Car idles fine but bogs out when you hit the fuel.

The following has been done.. well since March.

New Fuel Pump (Tank Cleaned as well)
New Fuel Filter
New Fuel Accumulator
New plugs and wires.

Replaced all the vacuum lines, sensors.. blah.. blah..

Recently:

Fuel Regulator (DMCMW)
Fuel Distributor (SpecialT)

Timing is set correct.. I know there's more I done but my mind is gone on vacation. Any suggestions would be helpful.

[dmc6960]

Well since you replaced the fuel distributor, did you set the mixture properly? Also check for vacuum leaks since you had all that stuff apart.

[dmc6960]

Also, have you checked the fuel pressures; primary and control?

Did this problem happen suddenly or has it always been like that since you got the car?

Any full diagnosis done before swapping out parts?

How do the injector spray patterns look?

[jawn101]

Is the frequency valve buzzing?

[jafo2k]

Well since you replaced the fuel distributor, did you set the mixture properly? Also check for vacuum leaks since you had all that stuff apart.

Not sure if mixture set right. Checking vacuum lines now.

[jafo2k]

Also, have you checked the fuel pressures; primary and control?

Did this problem happen suddenly or has it always been like that since you got the car?

Any full diagnosis done before swapping out parts?

How do the injector spray patterns look?

Injector spray looks all the same. Problem started since had car.

Dave at DMCMW walked me through a lot of tests. But since my location is so far away from help.. makes it hard.

[jafo2k]

Is the frequency valve buzzing?

Yes it is.

[jafo2k]

Also, have you checked the fuel pressures; primary and control?



Sorry missed this... pressures are ok.

[jafo2k]

Seems like I got vacuum issues.. like none. um.. hmmm

[jafo2k]

No vacuum to Fuel Regulator. hmm

[82DMC12]

I would replace all the vac hoses if you haven't yet. When I was going crazy chasing down a fuel problem about a decade ago I removed a hose only to find a small ball bearing shoved into it in order to turn vacuum off permanently to the vacuum advance. Yeah. You never know.

[WelmoedJ]

No vacuum to Fuel Regulator. hmm

By Fuel Regulator, you mean Control Pressure Regulator?
If you don't have vacuum there check the ThermoVac's vacuum connections (in from vac port at rear of left intake manifold; vac solenoid (at the back of the mixxture unit).
The one to the CPR has a junction in the vac line, could be disconnected there.
See vac diagram.

[dmc6960]

By Fuel Regulator, you mean Control Pressure Regulator?
If you don't have vacuum there check the ThermoVac's vacuum connections (in from vac port at rear of left intake manifold; vac solenoid (at the back of the mixxture unit).
The one to the CPR has a junction in the vac line, could be disconnected there.
See vac diagram.

And the "Thermo-Vacuum Switch" does just that, switches the vacuum when the engine warms up. You should have vacuum to the CPR when cold, and NOT when hot. Likewise you should have vacuum to the distributor advance when hot (and not at idle) but NOT when cold.

[DMC3165]

I know this might sound silly but have you checked your pickup screen in the fuel tank? I recently had an issue where my car would start to buck then bog down but only when hot. It took me a little while to track down but at the suggestion of Rob Grady I pumped the tank and found the pickup screen was in fact clogged solid. Interestingly enough the screen was only put in 2 1/2 years ago when 3165 first went back on the road. At that time I cleaned the tank and put in a new baffle. So I was really surprised to find this after only 16000 miles. I installed the new screen and its been good since.

[David T]

Did the car EVER run right? If you have done all of these things (and you did them right) it should be running OK. I would go back to the beginning and start by doing a compression test followed by a leak-down test and depending on the mileage and the results of the tests, maybe adjust the valves and replace the O2 sensor. Before going crazy, did you every put a dwell meter on and check the Lambda duty cycle? I would also verify TDC and check base timing and vacuum and mechanical advance.
David Teitelbaum

[DMCMW Dave]

Did the car EVER run right?

No - he started with someone else's basket case. Which makes things pretty complex.

[jafo2k]

And the "Thermo-Vacuum Switch" does just that, switches the vacuum when the engine warms up. You should have vacuum to the CPR when cold, and NOT when hot. Likewise you should have vacuum to the distributor advance when hot (and not at idle) but NOT when cold.

Ok.. then that works.

[jafo2k]

No - he started with someone else's basket case. Which makes things pretty complex.

That's putting it mildly. :) Time to get a Dwell meter!

[David T]

Because you took on a "basket case" you cannot assume ANYTHING is as it should be. Stop throwing parts at it in the vain hope that you will accidentally fix it. You have to now verify for yourself EVERYTHING. That starts with the mechanical. You will never get the motor running right if it is not healthy mechanically. Your next steps should be to inspect and adjust the motor till you know it is as it should be. Then you can start to work on the other systems.
David Teitelbaum

[jafo2k]

Because you took on a "basket case" you cannot assume ANYTHING is as it should be. Stop throwing parts at it in the vain hope that you will accidentally fix it. You have to now verify for yourself EVERYTHING. That starts with the mechanical. You will never get the motor running right if it is not healthy mechanically. Your next steps should be to inspect and adjust the motor till you know it is as it should be. Then you can start to work on the other systems.
David Teitelbaum

I should say some how the motor did run cause it was drove on to the transport carrier. However after installing "missing" parts in an attempt to return it back to normal.. then the issues started. How it ever ran, I'll never know, but it did and seemed to work fine.

[82DMC12]

Speaking of which, maybe start at the beginning such as check compression, valve lash, etc. So you know the motor is even capable of running right.

[jafo2k]

Speaking of which, maybe start at the beginning such as check compression, valve lash, etc. So you know the motor is even capable of running right.

Yes motor did run good until I started to replace missing parts.. we did compression check all ok.

[jafo2k]

I know this might sound silly but have you checked your pickup screen in the fuel tank? I recently had an issue where my car would start to buck then bog down but only when hot. It took me a little while to track down but at the suggestion of Rob Grady I pumped the tank and found the pickup screen was in fact clogged solid. Interestingly enough the screen was only put in 2 1/2 years ago when 3165 first went back on the road. At that time I cleaned the tank and put in a new baffle. So I was really surprised to find this after only 16000 miles. I installed the new screen and its been good since.

Thought of that but fuel pressure doesn't drop coming from tank. And it has a new filter as well. Besides for idling, it has no miles on it except for the ones we pushed. lol

[deloumis]

You mentioned you replaced vacuum lines, have you made sure they all go where they need to? Also make sure your spark plug wires are all going to the correct location.

Is your cat glowing when idling?

[dmc6960]

However after installing "missing" parts in an attempt to return it back to normal.. then the issues started.

I'm going to have to ask what this initially was. May shed some light onto what was done/bypassed to actually make it work.

[dmc6960]

Lets also get a few high resolution pictures of your engine compartment. Quite often we can point out something wrong by just that. Several angles, and several closeups of the fuel distributor, CPR, cold start tube, etc...

[jafo2k]

Hooked Dwell meter up.. stays at 45 .. doesn't move. CO2 sensor?

[jawn101]

Hooked Dwell meter up.. stays at 45 .. doesn't move. CO2 sensor?

If it stays at 45 during 'warm-up' (not moving at all? is it a digital meter?) then that is actually a good thing. If you hit the full throttle microswitch and the reading doesn't change (should jump to about 55 ish) then the microswitch is broken or disconnected.

If the engine warms up and the dwell stays at 45 steady then the O2 sensor is likely non-functional or disconnected.

Edit: clarity

[Bitsyncmaster]

Hooked Dwell meter up.. stays at 45 .. doesn't move. CO2 sensor?

It should stay at 45 until the O2 sensor has warmed up. If it's really cold it will stay higher (same as WOT) until warmed up. But you should see it swinging around 30 after it warms up (about 120 seconds of running).

[David T]

Once you can say the motor is OK then you have to figure it was something you did or did wrong. Maybe you screwed up the firing order or damaged an ignition wire. Maybe the distributor cap is not on right. Maybe you dropped a spark plug and messed up the gap or the plug is loose. There are too many things that could be wrong to list them all. You have to go over all of the work you did. To add to the complexity, with all of the parts you changed it is possible you have a bad part. That is another reason you don't change a lot of parts all at once if you can help it. The fact you are not getting any swing on the dwell meter could be the meter you are using, a wiring problem in the Lambda system, or it is just a symptom of another problem with the fuel system. If the frequency valve is buzzing the motor should be running better than you say it is even if the Lambda is not working exactly as it should.
David Teitelbaum

[jafo2k]

Once you can say the motor is OK then you have to figure it was something you did or did wrong. Maybe you screwed up the firing order or damaged an ignition wire. Maybe the distributor cap is not on right. Maybe you dropped a spark plug and messed up the gap or the plug is loose. There are too many things that could be wrong to list them all. You have to go over all of the work you did. To add to the complexity, with all of the parts you changed it is possible you have a bad part. That is another reason you don't change a lot of parts all at once if you can help it. The fact you are not getting any swing on the dwell meter could be the meter you are using, a wiring problem in the Lambda system, or it is just a symptom of another problem with the fuel system. If the frequency valve is buzzing the motor should be running better than you say it is even if the Lambda is not working exactly as it should.
David Teitelbaum

Never replaced all the parts at once. Sure wish there was a Delorean mechanic close by.. #@$@#!! Seems like I been over my work at least twice.. everything from plugs to wires. Hoses to connections. And I don't think the dwell meter I'm using is correct..

[jafo2k]

and if there is a Delorean Mechanic close... message me!! :)

[Dangermouse]

Never replaced all the parts at once. Sure wish there was a Delorean mechanic close by.. #@$@#!! Seems like I been over my work at least twice.. everything from plugs to wires. Hoses to connections. And I don't think the dwell meter I'm using is correct..

Many eyes make light work, or something like that:


Lets also get a few high resolution pictures of your engine compartment. Quite often we can point out something wrong by just that. Several angles, and several closeups of the fuel distributor, CPR, cold start tube, etc...

Jim and others are great at spotting stuff that is wrong, or just plain missing. :thumbup2:

(iirc in one thread recently, the engine was missing the entire throttle spool spring)

[Bitsyncmaster]

Never replaced all the parts at once. Sure wish there was a Delorean mechanic close by.. #@$@#!! Seems like I been over my work at least twice.. everything from plugs to wires. Hoses to connections. And I don't think the dwell meter I'm using is correct..

Sounds like the dwell meter is working. If the O2 sensor was disconnected the reading would also be locked at 45. Follow the wire on the O2 and see if it pulled off at the wheel well.

[David T]

You go over your work till you find the problem. The hard part is when you go over your own work you continue to miss your own mistakes. Best if you can get a fresh set of eyes on it but that isn't always possible. Try to look at it as if you didn't do anything and start all over. Be suspicious of everything. It could be as simple as while you were working in a tight area (like between the motor and the firewall) you knocked a hose or wire loose.
David Teitelbaum

[deloumis]

Never replaced all the parts at once. Sure wish there was a Delorean mechanic close by.. #@$@#!! Seems like I been over my work at least twice.. everything from plugs to wires. Hoses to connections. And I don't think the dwell meter I'm using is correct..

There's a ground wire in the back of the intake. I can't remember exactly what its for but it has to do with the fuel system. Its a quick check so worth a shot.
Also to check ignition what I do is get a timing gun and hook it up to the coil first and look at the light. It should be a steady strobe. Then hook it up to cylinder 1 and look at the light again. Should be a steady strobe again. Just repeat for all cylinders and if there is one with no light then you know something is wrong. Make sure the firing order is correct.

[dmc6960]

There's a ground wire in the back of the intake. I can't remember exactly what its for but it has to do with the fuel system.

That is the ground reference for the LAMBDA system. May have some red on the wire or connector. Yes, its important.

[jafo2k]

That is the ground reference for the LAMBDA system. May have some red on the wire or connector. Yes, its important.

Ground was already checked. All ok there. Going to start from scratch from the fuel pump back. I know it's going to be something stupid.

[dmc6960]

Pictures, and description of what was missing initially and what you installed first?

[dmc6960]

You mentioned you replaced vacuum lines, have you made sure they all go where they need to? Also make sure your spark plug wires are all going to the correct location.

Is your cat glowing when idling?

This too...

[jafo2k]

Pictures, and description of what was missing initially and what you installed first?

Yes, I'll do that. First installed was fuel pump, filter and accumulator only because the car sat so long. The other stuff I'll write down and try to get some pictures up asap

[jafo2k]

Some pictures. Yes the hose is missing between the cold start motor (regulator) and valve. The idle speed ECU is bad so was just by passing it for now. When I got the car there was no idle speed motor. (Mind you the car did run too) Most the vacuum lines were either missing or blocked off. Checked all vacuum lines 4 times including a camera to look under the intake to check connections.

All the sensors under the intake were replaced due to a fire from PO, which included a new engine harness. Water pump was replaced at same time.

New vacuum delay and hose to CSR
New CSR
Fuel Distributor
Pretty much all the temp sensors etc.. either broken and wires taped on.. etc.

Replaced solenoid value.. missing.

New wires (in correct order.. check three times)
New plugs (plugged to check gap.. all ok)

Don't bash me if I got a name of part wrong.. lol .. there is more when I think of it. But I'll be dam if this car is going to get the best of me!! Anyone want to come to Nova Scotia? lol

13175 13176 13177 13178 13179 13180

[jawn101]

Some pictures. Yes the hose is missing between the cold start motor (regulator) and valve. The idle speed ECU is bad so was just by passing it for now. When I got the car there was no idle speed motor. (Mind you the car did run too) Most the vacuum lines were either missing or blocked off. Checked all vacuum lines 4 times including a camera to look under the intake to check connections.

All the sensors under the intake were replaced due to a fire from PO, which included a new engine harness. Water pump was replaced at same time.

New vacuum delay and hose to CSR
New CSR
Fuel Distributor
Pretty much all the temp sensors etc.. either broken and wires taped on.. etc.

Replaced solenoid value.. missing.

New wires (in correct order.. check three times)
New plugs (plugged to check gap.. all ok)

Don't bash me if I got a name of part wrong.. lol .. there is more when I think of it. But I'll be dam if this car is going to get the best of me!! Anyone want to come to Nova Scotia? lol

13175 13176 13177 13178 13179 13180

Do you have a plug for the mixture adjustment screw (small hole in the top of the mixture unit, just in front of the fuel distributor)

Edit: Misread what you said there. Removed one question

[jafo2k]

Do you have a plug for the mixture adjustment screw (small hole in the top of the mixture unit, just in front of the fuel distributor)

Edit: Misread what you said there. Removed one question

Yes, I have a plug but it is out right now.

[dmc6960]

This is why a picture is SOOOOOOOO helpful. It appears that your fuel supply line is in the wrong port. It is currently attached DIRECTLY to the fuel return line. See here...

http://www.dmcnews.com/Techsection/fuelhoses.htm

EDIT: NEVERMIND!!! I was wrong. So many black hoses...

[dmc6960]

Also the electrical plug for the vacuum solenoid isn't seated properly. Pull the rubber boot back when inserting it, then slide it back over.

[dmc6960]

This is why a picture is SOOOOOOOO helpful. It appears that your fuel supply line is in the wrong port. It is currently attached DIRECTLY to the fuel return line. See here...

http://www.dmcnews.com/Techsection/fuelhoses.htm

Whoops, my bad, so many hoses look alike. I dont think this is the case, but always worth a doublecheck.

[jafo2k]

This is why a picture is SOOOOOOOO helpful. It appears that your fuel supply line is in the wrong port. It is currently attached DIRECTLY to the fuel return line. See here...

http://www.dmcnews.com/Techsection/fuelhoses.htm

EDIT: NEVERMIND!!! I was wrong. So many black hoses...

I was running for the car thinking how embarrassed i was going to be.. hehe

[jafo2k]

Fuel Pump.. checked everything correct. Reinstalled double checked hoses. All correct. Filter clean. Headed to accumulator.

[WelmoedJ]

And the "Thermo-Vacuum Switch" does just that, switches the vacuum when the engine warms up. You should have vacuum to the CPR when cold, and NOT when hot. Likewise you should have vacuum to the distributor advance when hot (and not at idle) but NOT when cold.

Thanks, Jim, for completing my answer.
Had forgotten that.

[jafo2k]

Well, tested fuel injectors with old fuel distributor.. but with new distributor showed 3 bad. Had 3 here that came with the car.. replaced and the engine was running fine!! Put everything back in place and got ready for test drive... my battery was dead.. hehehehe!!! to be continued............. after I charge the battery up. (Darn hood light.. lol)

[klaatu42]

Hi. Well, I am the latest owner of #3133 and this saga continues. It's taken some doing to fix some of the issues caused before I got it (some fuel lines were on incorrectly, etc.), plus some new issues that I didn't see listed in this thread. I couldn't get anything out of her until I fixed up some wiring issues, some of which was caused by a botched audio installation.

The frequency valve was not buzzing until I reseated it several times. The RPM relay had (still has, but I've put in a temporary fix) a bad socket at the fuel pump connection, and I'm now suspecting a bad alternator as well (no battery light, and getting 9V in a lot of places when cranking).

The vehicle will start, rev up high as it should, but then dies rather than idling 1-2 seconds later.

Not sure where I'm going from here, but I'm thinking lambda relay or ECU...

EDIT: I should add that I also have #11633, which is an automatic that runs perfectly, which I can use for reference, or for careful temporary part swaps!

[SS Spoiler]

Check for poor connection on ballast resistors on back firewall.[long white thingys]

[klaatu42]

I don't seem to have a poor connection here, but I DO seem to have fewer connections than I do on 11633, and it's definitely possible that these are just plain bad...

35133

So it would seem that the engine doesn't run for a specific amount of time before dying... it is revving up to a certain RPM and then dying. So if it takes a bit to start and ramp up, it runs longer. If it starts quickly and ramps up fast, it shuts off faster.

Am I right in thinking that the cold start valve would be feeding it fuel and it is dying when the valve shuts off?

I will have to look into the procedure for checking to be sure that my injectors are spraying.

[David T]

I don't seem to have a poor connection here, but I DO seem to have fewer connections than I do on 11633, and it's definitely possible that these are just plain bad...

35133

So it would seem that the engine doesn't run for a specific amount of time before dying... it is revving up to a certain RPM and then dying. So if it takes a bit to start and ramp up, it runs longer. If it starts quickly and ramps up fast, it shuts off faster.

Am I right in thinking that the cold start valve would be feeding it fuel and it is dying when the valve shuts off?

I will have to look into the procedure for checking to be sure that my injectors are spraying.

You are probably on the right track but the other possibility is when it starts the ignition is running on the bypass and when you stop cranking you lose ignition voltage and the motor stops. Can you keep it running by holding down the air sensor plate? If so it is a fuel problem.

[Bitsyncmaster]

CSV only can fire when your cranking on the starter. It delivers very little fuel so when you release the starter it would not run at all if you needed the CSV for fuel.

[klaatu42]

I have in the past been able to keep the engine running indefinitely by delivering 12V to the CSV. The moment it is disconnected, the engine stops.

There are more wiring issues I need to sort out for sure, because the battery light (and other indicator lights) do not come on when the key is turned. Somebody did quite the number on this car, including using wood screws to attach trim, etc. and spray painting INSIDE the passenger compartment. I'm putting in a whole new center console because of that!

[DMCMW Dave]

I have in the past been able to keep the engine running indefinitely by delivering 12V to the CSV. The moment it is disconnected, the engine stops.

There are more wiring issues I need to sort out for sure, because the battery light (and other indicator lights) do not come on when the key is turned. Somebody did quite the number on this car, including using wood screws to attach trim, etc. and spray painting INSIDE the passenger compartment. I'm putting in a whole new center console because of that!

That means you were running the engine entirely on the CSV, and the fuel distributor and/or injectors are likely plugged or otherwise not functional.

It's somewhat dangerous to run it on the CSV for a long time as the fuel distribution is very uneven. Some cylinders are extremely rich and some extremely lean. It's only intended as a quick shot to start a cold engine.

[David T]

That means you were running the engine entirely on the CSV, and the fuel distributor and/or injectors are likely plugged or otherwise not functional.

It's somewhat dangerous to run it on the CSV for a long time as the fuel distribution is very uneven. Some cylinders are extremely rich and some extremely lean. It's only intended as a quick shot to start a cold engine.

Agreed, if you can keep it running on the CSV you have a fuel system problem so do not bother to troubleshoot the ignition system. Jumper the fuel pump to run, pull an injector and push on the air sensor plate. See if the injector squirts.

[klaatu42]

Unfortunately, it was "in the past" that I was able to get it to run from the CSV. After sitting in cold storage for the winter, it came back out with a couple of chewed wires from an animal (ugh) and some other wiring/voltage issues that I'm still trying to track down. There were some pretty bad wiring issues I've found so far, including live 12V wires that were just twisted together – no solder, no crimp, not even tape! Also a couple of grounds weren't even tightened down, so they were just spinning loose on bolts.

Definitely cleaning up several previous owners' messes on this one. So glad I've got 11633 to drive when I get tired of fiddling.

Will pull the injectors again soon (currently sick and stuck indoors). They were not squirting at all last time I tried that. Just a couple of drips after a minute or so. I do get some resistance when pushing down on the plate after the fuel pump has been running.

[klaatu42]

I should add...

Did some of the '81s have no jump post? 3133 has none.

[David T]

I should add...

Did some of the '81s have no jump post? 3133 has none.

It had one, and was removed. All Deloreans had them. I am sure if you look you will find traces. Is there a label still in the car?

[klaatu42]

Thanks. Good point... The covers and stickers on 3133 are mostly removed. I received the vehicle with a lot of these in a box or just thrown into the trunk. I'm sure the jump instructions will indicate the post was there.

I'm heading out to pull, clean, and reinstall the instrument cluster because none of the indicators are functioning. Without fixing things up to at least get the battery light working, I know nothing else is going to be functioning correctly. I hate working on more than one part of a vehicle at a time (for fear of introducing any new problems that I can't detect until she's running), but on this vehicle, it looks like I don't have much choice!

[DMC5180]

Is there a hole in the pontoon where the jump start post should be?

[klaatu42]

Oops. Yup. Forgot to jump back on the thread to say that yes, it's there. Oddly, though, there are no marks on the hole whatsoever from a previous bolt.

Since this thread is "Fuel problem", I started a new one for the electrical issue I found while doing this...
http://dmctalk.org/showthread.php?12107-Bad-Alternator

[klaatu42]

Agreed, if you can keep it running on the CSV you have a fuel system problem so do not bother to troubleshoot the ignition system. Jumper the fuel pump to run, pull an injector and push on the air sensor plate. See if the injector squirts.

Ooo! This is encouraging. I must have done something right recently, because I do now get quite the spray. A week ago I was getting nothing. I find what you have said below quite intriguing. Could this in any way be related to the bad alternator issue it's got? (No battery light when key turned, but I do get light if I ground the warning light wire)


You are probably on the right track but the other possibility is when it starts the ignition is running on the bypass and when you stop cranking you lose ignition voltage and the motor stops. Can you keep it running by holding down the air sensor plate? If so it is a fuel problem.

Is there a way I can test the theory above re the bypass and losing ignition voltage? If necessary, I can temporarily use parts from 11633 for testing purposes.

Would it be safe to defeat the relay by jumping across the lower resistor terminals (white to blue/yellow) just for a quick test or would that be dangerous?

[klaatu42]

Aha! I cannot keep the engine running by pressing down on the air sensor plate. It does, however, start more easily and run a bit better on the next start attempt... I think you might be right about losing ignition voltage.

I've lost the light out there and the mosquitos are killer (no garages until we move to our new place in two weeks) so I will have to continue tomorrow... but I'm very enthusiastic that you've got me on the right track at last.

[klaatu42]

Aaaaand #3133 has moved on, beginning yet another new chapter in its long and complicated life. This time, she will ride again. Wells Auto has acquired 3133 and I have every confidence they will bring her back to life. Clearly, somebody did something unfortunate to her a few owners ago. I am looking forward to seeing what becomes of her.

With a house move, and some other vehicle restorations in progress, I simply didn't have the time or space to keep tinkering and playing detective. Wells has the know-how and can provide the TLC that I currently cannot.

Wishing 3133 all the best!

In the meantime, 11633 is doing great, lol

[Wells Auto]

Aaaaand #3133 has moved on, beginning yet another new chapter in its long and complicated life. This time, she will ride again. Wells Auto has acquired 3133 and I have every confidence they will bring her back to life. Clearly, somebody did something unfortunate to her a few owners ago. I am looking forward to seeing what becomes of her.

With a house move, and some other vehicle restorations in progress, I simply didn't have the time or space to keep tinkering and playing detective. Wells has the know-how and can provide the TLC that I currently cannot.

Wishing 3133 all the best!

In the meantime, 11633 is doing great, lol


Indeed sir! Will keep you posted, 3133 will live again ;)