Need help with this one.

[irarref215]

Hey there auto community! My name is Eric and I live in the PNW.

I finally found an 81 close to my area. I have never seen the engine run correctly. The PO made attempts to fix the problem, and when I got it, it had the problems it has now. It will start, idle high at about 1500 and settle down to a reasonable idle. Cracking the throttle (I would assume coming off the idle switch) causes the engine to chug, backfire through the intake and blow unburnt fuel out the exhaust. It is pretty violent how this happens. The PO was revving it up as he was demonstrating this for me and I could see something was wrong. So the car will idle, but that is all it will do. When asking for help, people are asking what it does when I drive it. It has not gone anywhere in years. I would not attempt to drive it like that. I would not let it warm up, since it reeks of fuel. I went to see it and he told me all the things he 'fixed' with the car. They included:

Fuel plump replacement/cleanout
Spark plugs
Fuel distributor
He had been messing with the idle screw trying to get it to run right


I did these things:

verified I had a poor spray and volume from injectors so I replaced all of them
replaced the ignition coil since it seems like an ignition problem.
Verified I have 78 lbs to the distributor with the jumper
Fixed many vacuum leaks including some missing parts left out by the PO
Verified the distributor is at #1 and crank
verified firing order and plug wires ok
spark plugs
New fuel lines
fuel filter

Findings:

FV not buzzing, but something else is near the AC compressor
Tried the dwell meter but the needle did not move
Plunger in distributor operational

I have been told CPR and disassembled this partially, found the diaphragm was not sealing from aluminum corrosion. Good now, holds vacuum on both ports. Any ideas?

[sdg3205]

You need to re-establish a baseline mixture. Is the factory mixture plug still in place on the mixture unit or do you see a CO plug (looks like a question mark)? May also be a golf tee!

EDIT - not sure what you mean "distributor at number 1." Have you verified timing with a gun? Also, have you traced plug wires to distributor cap and is the cap on correctly and NOT 180 off?

Where are you in the PNW?

[Bitsyncmaster]

Sounds like your lambda system is not working. Most common fault for that is someone put the wrong relay into the lambda relay socket. Next fault is the RPM relay if it has the double contacts (which original ones had).

But even with the lambda back working, your mixture is probably way off and will need adjustment once the lambda is fixed.

[irarref215]

You need to re-establish a baseline mixture. Is the factory mixture plug still in place on the mixture unit or do you see a CO plug (looks like a question mark)? May also be a golf tee!

EDIT - not sure what you mean "distributor at number 1." Have you verified timing with a gun? Also, have you traced plug wires to distributor cap and is the cap on correctly and NOT 180 off?

Where are you in the PNW?

I see a rubber coned plug on the mixture unit. I think it idles OK so doesn't this screw just adjust idle? Does it have an effect off idle? I pulled the mixture unit off again and the #1 mark on the distributor lines up with the TDC mark on the crank. So the distributor is indexed correctly. I am from the Portland, Oregon area. I have read every thread regarding fuel delivery. I have spoken with some 'gurus' on this and can not get people to talk about this problem. Is this the way it is supposed to work? I find it hard to believe anyone would buy a car with the PRV engine if it reeked of fuel and backfired through the intake when cold. Maybe I should let it warm and see what kind of surprises I get.

Thank you for your reply.

[Jonathan]

The rubber coned plug sounds like your mixture has been adjusted in the past. That mixture screw doesn't affect idle directly. It doesn't affect what the O2 sensor reads in your exhaust stream directly either, but that is what you adjust for. I'd suggest you read the fuel and lambda systems descriptions in the workshop manual and make note of the diagrams. It will show you a side profile of what that screw does and the lever arm underneath and what it affects. It mostly changes fuel pressures, on both sides of the equation.

I would suggest figuring out how to get your frequency valve buzzing. You can test by jumpering the power on via the RPM relay receptacle. Once that is in place, you don't need the ignition on to have power going to the frequency valve. You should easily hear it buzzing, especially so since the engine won't be on and making any noise. It could be as simple as the connector (electrical) is not making good contact. That could be the source of your fuel smell.

If you are indeed getting unburnt fuel directly out your exhaust, and not just condensation, your catalytic convertor might be in bad shape. You likely need to replace your O2 sensor before all of this is said and done too. You should/can get your lambda system to respond properly without a new one in there. Once everything is better, then put the new one in.

If your engine is truly doing something violent and dangerous, then proceed at your own risk, but adjusting the mixture to somewhere "about" in the middle of rich and lean to at least let you continue with the troubleshooting would be ideal. My mixture adjustment went from stall to stall in only one half of a turn. I don't know if there are physical stops if you were to try and get it in the middle of those two ends while doing it with the engine off. Turn it rich to the right and lean to the left (rich = clockwise and lean = counterclockwise). I suspect you want to lean out your mixture by turning it left (counterclockwise). Try small changes, like in terms of minutes on a clock, not hours, as you only have "6 hours" from stall to stall.

The dwell needle not moving isn't that bad of a sign. Might just mean your O2 sensor is fouled, or not warmed up, or some other issue with the Lambda ECU that a couple of us have seen recently for whatever reason.

[sdg3205]

Dave M makes a good point. Double check the lambda system is actually getting power. Other than the wrong relay being in the socket, the spade connectors on the back of the socket can work themselves out the back. Check AND clean the pins at the bulkhead very well. If you establish you have power the frequent valve could be seized. If so, hit it with a hammer.

Once everything is powered and operating take the injectors out and place them in clear jars. Jump the fuel pump at the rpm relay and adjust the mixture screw to lean until they stop spraying. This is your new baseline. Reinstall the injectors and proceed with mixture adjustment and dwell procedure.

I have no idea what u mean by people not wanting to talk about this problem. Fuel delivery problems are probably the number one topic on this forum.

[David T]

Dave M makes a good point. Double check the lambda system is actually getting power. Other than the wrong relay being in the socket, the spade connectors on the back of the socket can work themselves out the back. Check AND clean the pins at the bulkhead very well. If you establish you have power the frequent valve could be seized. If so, hit it with a hammer.

Once everything is powered and operating take the injectors out and place them in clear jars. Jump the fuel pump at the rpm relay and adjust the mixture screw to lean until they stop spraying. This is your new baseline. Reinstall the injectors and proceed with mixture adjustment and dwell procedure.

I have no idea what u mean by people not wanting to talk about this problem. Fuel delivery problems are probably the number one topic on this forum.

Other possible reasons for the frequency valve not to buzz include a bad connection at the plug to the valve and if the mixture is way off. Remove and replace the plug a few times, that usually gets it going if that is the problem. There is a procedure to roughly adjust the mixture screw to get it close so you can fine tune it with a dwell meter once you get the frequency valve going. Do you feel resistance when you push on the air sensor plate? If not, the fuel plunger may still be stuck. If the plunger is stuck the mixture will be VERY rich. You will see the muffler turn red if you let the motor run long enough.

[irarref215]

Other possible reasons for the frequency valve not to buzz include a bad connection at the plug to the valve and if the mixture is way off. Remove and replace the plug a few times, that usually gets it going if that is the problem. There is a procedure to roughly adjust the mixture screw to get it close so you can fine tune it with a dwell meter once you get the frequency valve going. Do you feel resistance when you push on the air sensor plate? If not, the fuel plunger may still be stuck. If the plunger is stuck the mixture will be VERY rich. You will see the muffler turn red if you let the motor run long enough.


Thank you everyone for your help. The help I have asked for so far has been on the phone only. Seems like people were just too busy to talk on a land line, even some that I have spent money and done business with in the past. This is the first time I have solicited help from the net.

The Frequency Valve looks like an injector and I tested it with my injector simulator. It feeds a 50% duty squarewave to it and it is useful for cleaning in the ultrasonic bath. It does work by itself. I have excellent connections right at the Frequency Valve as I see others have had issues in this area.

I feel resistance when I press the sensor plate, I believe the plunger is working fine. I have run an injector volume/spray test and it appears to operate as it should. I will set the idle screw as suggested by David T, just at the point it stops spraying fuel.

I guess the question I have now is that when I was doing the flow test for the injectors, I jumpered out 30 and 87 terminals I believe. Is this supposed to get the frequency valve to buzz? If so, it wasn't.

No doubt that the Cat is probably plugged at this point. It still would not account for the engine being able to idle just fine, but just cracked off idle it dies and backfires. Is there anything in the valley that could cause this? I have not pulled the entire intake off but there is some thermally operated switches in there. Could they cause such a problem? Want to check before I put the mixture unit back on again (5X already) and discover it still has the problem.

[Bitsyncmaster]

You jumper the brown wire to the double white/red wires on the RPM relay socket to power up the lambda.

You should get a buzz of 50% duty cycle when you do that jumper.

[axh174]

You jumper the brown wire to the double white/red wires on the RPM relay socket to power up the lambda.

You should get a buzz of 50% duty cycle when you do that jumper.

+1 on this.

I had a similar problem when the connection at my frequency valve got corroded. Idling was fine, but as soon as I left off the idle speed switch, the engine would sputter and choke. Jumpering the RPM relay pins is what helped me track down the problem (I could hear the lambda relay closing, but no valve buzzing. Following the circuit to the valve revealed the corrosion).

If you've jumpered the RPM pins and don't hear the valve buzzing, do you hear the relay clicking?

A helpful resource is the Lambda Circuit diagram found 3/4 of the way down in this (http://dmctalk.org/showthread.php?40-All-Wiring-Schematics) post (DMCTalk Resources).

[DTOUR]

Since the car has never run right for you, and the previous owner replaced the fuel pump, do a simple check and make sure the input/return fuel lines are not crossed. The pump will put out sufficient pressure to "back feed" the fuel system and allow an idle condition. Anything beyond that and the engine will not sound happy at all, and probably stall. This is not to say the engine will just start up and run fine at idle. It won't! If one of your "cats" is getting red hot - big clue there too.

VERIFY your fuel lines are connected properly!
(Ask me how I know this...) Don't trust what the Previous Owner did!

[mluder]

Welcome to DeLorean ownership.
I'm also in the immediate Portland area - Happy Valley actually. I'm by no means an expert on the DeLorean operations but have learned a few things in the 4 years I've owned my car. There's another member of the forum who lives in Hillsboro and has been an owner for much longer who I often turn to for advice. He and I occasionally get together to work on little bits here and there or sometimes to just go for a drive. I'm not saying we could be of help, but we're often up for trying.

At any rate we're both members, along with some other locals, of the Pacific Northwest DeLorean Club. http://www.pndc.org The club is headquartered in the Seattle area and the oldest contiguously running DeLorean club in the world and . It's only $20 a year to join and gets you access to many club events but more importantly access to "expert" owners including tech sessions hosted by members and aided by Toby Peterson from the DeLorean shop up in Seattle. This is a great opportunity to get some guided time to work on your car. Toby comes down to the Portland area once a year for a session in Forest Grove at the home of a local owner who's sort of the local guru when it comes to all things DeLorean.

My schedule is a bit busy but feel free to PM me if you'd like to get together sometime.

Cheers
Steven

[irarref215]

Welcome to DeLorean ownership.
I'm also in the immediate Portland area - Happy Valley actually. I'm by no means an expert on the DeLorean operations but have learned a few things in the 4 years I've owned my car. There's another member of the forum who lives in Hillsboro and has been an owner for much longer who I often turn to for advice. He and I occasionally get together to work on little bits here and there or sometimes to just go for a drive. I'm not saying we could be of help, but we're often up for trying.

At any rate we're both members, along with some other locals, of the Pacific Northwest DeLorean Club. http://www.pndc.org The club is headquartered in the Seattle area and the oldest contiguously running DeLorean club in the world and . It's only $20 a year to join and gets you access to many club events but more importantly access to "expert" owners including tech sessions hosted by members and aided by Toby Peterson from the DeLorean shop up in Seattle. This is a great opportunity to get some guided time to work on your car. Toby comes down to the Portland area once a year for a session in Forest Grove at the home of a local owner who's sort of the local guru when it comes to all things DeLorean.

My schedule is a bit busy but feel free to PM me if you'd like to get together sometime.

Cheers
Steven

Wow now look at all this help. I was getting the feeling that this community of car people was not going to be healthy for me. I might know one of the people you speak of in the Portland area. I have much experience with EFI setups, mostly from the GM corner. This CIS system is something I have always wanted to learn, and now I feel fully immersed as well as confused.

I see on the diagram where the WUR and FV get their power from. I will power up the lambda and see if I can get this thing to oscillate. I believe I have a bad connection somewhere as if the FV is not oscillating, it will meter full pressure from the distributor, hence the rich mixture. I have 78 pounds of pressure measured from the center from the distributor so the fuel pump must be connected properly. I will recheck that too. Thank you again for all your help everyone.

[sdg3205]

It's a great community. Sorry you had a negative initial experience. As Steve said, the PNDC is a great club. Why the wife and I are even going to the Xmas party in Seattle this coming weekend.

[Ron]

Welcome!!


Sounds like: check the control pressure, warm it up, check CP again, lean it out (CCW) until the dwell shows the system kick in....

[mluder]

Why the wife and I are even going to the Xmas party in Seattle this coming weekend.

Are you coming down? Crap! We can't go so it looks like we won't get a chance to meet again...

One day, Mr. Graham... One day.

Cheers
Steven

[sdg3205]

Are you coming down? Crap! We can't go so it looks like we won't get a chance to meet again...

One day, Mr. Graham... One day.

Cheers
Steven

Single tear.

[irarref215]

Ok so getting pretty good at taking apart/reassemble. The frequency valve itself was not working, got it working again. Now it isn't dumping fuel as bad. It still is backfiring through the intake when accelerated. I guess I let it warm up and try to tune it from here. Thanks for your help.

[fnzen]

QUESTIONS
are the plug wires new?
new rotor?
new cap?

if no or unknown just replace

the "mixture" screw is on the fuel distributor under the plug
when the plug is removed while running does the "idle" change? can you feel a vacuum?
make sure the plug "plugs"

is the vacuum solenoid working? turn key on but not to start, hold the solenoid and manually move the throttle you should feel it click each time you move the throttle

if you are smelling gas , move each fuel line "covering" gently back to see if any of the lines have a slight leak

are you sure the ground is good from the ballast resistor

[Bitsyncmaster]

I see on the diagram where the WUR and FV get their power from. I will power up the lambda and see if I can get this thing to oscillate. I believe I have a bad connection somewhere as if the FV is not oscillating, it will meter full pressure from the distributor, hence the rich mixture. I have 78 pounds of pressure measured from the center from the distributor so the fuel pump must be connected properly. I will recheck that too. Thank you again for all your help everyone.

You should get 70 to 80 PSI testing primary pressure via a gauge connected on the center post. To read control pressure, the gauge stays on that center post but the line is opened also on the gauge to the WUR. Just want to make sure you have the gauge setup with the shut off valve in the line. Typical control pressure starts around 20 PSI with a cold engine and warms up to about 50 PSI.

[irarref215]

QUESTIONS
are the plug wires new?
new rotor?
new cap?

if no or unknown just replace

the "mixture" screw is on the fuel distributor under the plug
when the plug is removed while running does the "idle" change? can you feel a vacuum?
make sure the plug "plugs"

is the vacuum solenoid working? turn key on but not to start, hold the solenoid and manually move the throttle you should feel it click each time you move the throttle

if you are smelling gas , move each fuel line "covering" gently back to see if any of the lines have a slight leak

are you sure the ground is good from the ballast resistor

The plug wires are new, MSD and measure ~ 1K with ohmmeter. New cap, new rotor inspected OK.

I will check for vacuum at the rubber plug. Probably creates a pretty good leak if not on.

I assume the vacuum solenoid you are referring to is for the distributor advance. This only operates when the thermal vacuum valve is warm. I am just trying to get the car to cease backfiring through the intake before I let it warm. However... the diaphragm inside the solenoid was breached. It was drawing vacuum from the electrical plug on the solenoid. It was so leaky that it would not actuate the advance mechanism inside the distributor when sufficient vacuum applied to the input port of the solenoid. Ordered a solenoid from DMC Europe, as well as ONE of the spacers that is in between the 'W' pipe and the mixture unit that was missing from the PO. I believe I don't have any more leaks, although I will put on a gauge tonight and see if I have ~19 in/hg at idle.

The fuel I am smelling is coming out of the exhaust. I have checked all my fuel connections and don't see any leakage, just a strong unburnt fuel smell coming from the exhaust. I can rev it up now that the FV is working, but coaxing it to higher RPM's causes backfires in the in the intake that makes the sensor plate flutter. Is this normal?

[DMCMW Dave]

I can rev it up now that the FV is working, but coaxing it to higher RPM's causes backfires in the in the intake that makes the sensor plate flutter. Is this normal?

No. Without seeing it in person, I'd hazard a guess that you have a couple of bad injectors or a bad fuel distributor. It's leaning out at higher RPM but not very evenly.

[irarref215]

No. Without seeing it in person, I'd hazard a guess that you have a couple of bad injectors or a bad fuel distributor. It's leaning out at higher RPM but not very evenly.

When I first got the vehicle, it had very poor spray patterns, and different volume between them. I also noticed some rust on the interior of the banjo fittings. I attempted to have the injectors cleaned and this worked initially. They eventually clogged again. The screens inside the injectors had rusted and clogged the valve causing poor spray patterns again. These injectors were bad. I replaced all of them. I replaced all of my fuel lines. I ran a flow test that resulted in great spray pattern and 6oz/minute of flow wide open. Very even volume between all injectors. This I believe to be stable. Not sure if the distributor can be affected by low flow rates with foreign debris inside. I have not had that apart.

Forgot to mention I did run a compression test that resulted in 177 +/- 5 psi per cylinder.

[DMCMW Dave]

When I first got the vehicle, it had very poor spray patterns, and different volume between them. I also noticed some rust on the interior of the banjo fittings. I attempted to have the injectors cleaned and this worked initially. They eventually clogged again. The screens inside the injectors had rusted and clogged the valve causing poor spray patterns again. These injectors were bad. I replaced all of them. I replaced all of my fuel lines. I ran a flow test that resulted in great spray pattern and 6oz/minute of flow wide open. Very even volume between all injectors. This I believe to be stable. Not sure if the distributor can be affected by low flow rates with foreign debris inside. I have not had that apart.

Forgot to mention I did run a compression test that resulted in 177 +/- 5 psi per cylinder.

Everything "sounds" right but anytime I've seen that "flutter" thing happen, and high speed lean-out, it has been injectors or FD. Or a massive vacuum leak, but that usually presents other issues as well.

A sticky fuel distributor plunger will cause some pretty odd behavior, and will pass a flow test just fine.

If it's been a while, repeat the flow test on the car. You may have had more stuff in the system break loose since you first did this.

[Ron]

I will check for vacuum at the rubber plug. Probably creates a pretty good leak if not on. Don't forget to plug the hose that went to the breather...

[dn010]

Any time I had the smell of fuel or raw fuel coming from my exhaust, it was due to a bad fuel distributor - this happened twice to me. If you can find a known good one to swap out for, at least you'd have 1 thing checked off your list of possible causes.

[David T]

Any time I had the smell of fuel or raw fuel coming from my exhaust, it was due to a bad fuel distributor - this happened twice to me. If you can find a known good one to swap out for, at least you'd have 1 thing checked off your list of possible causes.

Another thing that can cause backfiring is if the timing off or the mechanical or vacuum advance is not working right. Other possibilities include bad ignition wires, bad coil, bad cap and rotor, and bad spark plugs.

[irarref215]

Another thing that can cause backfiring is if the timing off or the mechanical or vacuum advance is not working right. Other possibilities include bad ignition wires, bad coil, bad cap and rotor, and bad spark plugs.

Precisely. Thats what I thought as well. I will say that there is much 'misinformation' on this site as to how this engine functions. I decided to put a timing light on the crank and noticed COLD (no advance because the thermal valve was not warm yet) and the timing was pretty close to zero. Retarded the timing to 13 degrees. Let the vehicle warm for the first time, removed and plugged the vacuum line to the advance diaphragm, retimed when I could get the idle low enough and it was still about 13 degrees. I assume like any vehicle you check the timing without any vacuum advance? I have the full manual and it doesn't give this information. I think with these engines it assumes a basic understanding on how a multi-cylinder engine operates and build from there. I have a ways to go before it is running right, and I might rebuild the fuel distributor since it is the only place in the fuel system I haven't been. Need to now start checking CPR pressures now that the ignition is right, and set the duty cycle. Left bank (1,2,3) has a slight miss that I can feel against the tailpipe.

I did take my first drive, and it goes pretty good, especially if you put some gas in the tank before you leave the house :(. I think I will contact the PNW Delorean club and make some new friends. Thank you everyone for your help, these last couple months have been enlightening.

[Ron]

I assume like any vehicle you check the timing without any vacuum advance? I have the full manual and it doesn't give this information. I think with these engines it assumes a basic understanding on how a multi-cylinder engine operates and build from there.
Yes. Unlike some later model vehicles, there should be no vacuum there at idle. But, it's a good idea to disconnect it, just in case the solenoid leaks, etc, and, for checking the mechanical advance function while you are there.

[Bitsyncmaster]

I did take my first drive, and it goes pretty good, especially if you put some gas in the tank before you leave the house :(. I think I will contact the PNW Delorean club and make some new friends. Thank you everyone for your help, these last couple months have been enlightening.

It sounds like you have a pretty good understanding of the PRV engine now. Glad your making progress.

[David T]

It sounds like you have a pretty good understanding of the PRV engine now. Glad your making progress.

If you need the step-by-step procedure here it is:
Disconnect and plug the vacuum line to the distributor vacuum advance capsule.
Clean the timing marks.
Connect to cyl #1
Start the motor and verify 13 degrees at 775 RPM's or less so the mechanical advance is not coming in.
This is in the Workshop Manual M:01:02
NOW increase the RPM's and check the timing.
At 1000 no advance
At 2000 10 degrees
At 3000 14 degrees
At 4000 20 degrees
These are of course + 13 so for example at 2000 you should see a total of 13 + 10 or 23 degrees.

Now go back to idle and apply vacuum to the vacuum advance capsule
At 5" 3 degrees
At 10" 12 degrees
At 15" 20 degrees.
Again, you need to add 13 to these #'s

Hook up the vacuum line.
These specs are on M:01:04
Add a couple of drops of oil to the wick under the rotor.
If you don't get these results you have to find out why and fix it. Without the proper advance (vacuum AND mechanical) you will not get all of the power you should have, the motor will overheat and knock, and your gas mileage will be low.

[irarref215]

If you need the step-by-step procedure here it is:
Disconnect and plug the vacuum line to the distributor vacuum advance capsule.
Clean the timing marks.
Connect to cyl #1
Start the motor and verify 13 degrees at 775 RPM's or less so the mechanical advance is not coming in.
This is in the Workshop Manual M:01:02
NOW increase the RPM's and check the timing.
At 1000 no advance
At 2000 10 degrees
At 3000 14 degrees
At 4000 20 degrees
These are of course + 13 so for example at 2000 you should see a total of 13 + 10 or 23 degrees.

Now go back to idle and apply vacuum to the vacuum advance capsule
At 5" 3 degrees
At 10" 12 degrees
At 15" 20 degrees.
Again, you need to add 13 to these #'s

Hook up the vacuum line.
These specs are on M:01:04
Add a couple of drops of oil to the wick under the rotor.
If you don't get these results you have to find out why and fix it. Without the proper advance (vacuum AND mechanical) you will not get all of the power you should have, the motor will overheat and knock, and your gas mileage will be low.

Thank you David T for making this information available. Following this should insure both mechanical and vacuum advance are working as they should.

[irarref215]

OK so I have had this car for a year now. I work on it frequently. I got the ignition working good. It still had hard starts and would not idle when cold. Injector volume was all over the place. Purchased 6X injectors. Still varied in volume. Had the fuel distributor rebuilt. Now, with a CIS fuel pressure tester, I have 68 PSI with the valve open or closed. Crack an outlet fitting for the WUR and the pressure does not change with the CIS valve open. Cleaned the screen on the WUR, disassembled and verified that it will flow. I cannot get the control pressure below the main regulator. The only way I can get the control pressure down is to crack a line going into the WUR, and it will go down. The outlet of the WUR has no effect on regulating control pressure. Diassembled the WUR and cleaned it out. Screen was clogged. Should I try to remove the screen and put another in? I poked a pin in it and it seemed to flow. Thinking it might be too restrictive. but that diaphragm in there is very restrictive. The guy I got the car from worked on the car for 8 years or so. Anything could be suspect. Any ideas on how to lower the control pressure? Does the engine have to be running for the control pressure to come down? I certainly have not heard the engine run, I don't know how I would get it started, it just cranks and cranks.

[irarref215]

OK so I have had this car for a year now. I work on it frequently. I got the ignition working good. It still had hard starts and would not idle when cold. Injector volume was all over the place. Purchased 6X injectors. Still varied in volume. Had the fuel distributor rebuilt. Now, with a CIS fuel pressure tester, I have 68 PSI with the valve open or closed. Crack an outlet fitting for the WUR and the pressure does not change with the CIS valve open. Cleaned the screen on the WUR, disassembled and verified that it will flow. I cannot get the control pressure below the main regulator. The only way I can get the control pressure down is to crack a line going into the WUR, and it will go down. The outlet of the WUR has no effect on regulating control pressure. Diassembled the WUR and cleaned it out. Screen was clogged. Should I try to remove the screen and put another in? I poked a pin in it and it seemed to flow. Thinking it might be too restrictive. but that diaphragm in there is very restrictive. The guy I got the car from worked on the car for 8 years or so. Anything could be suspect. Any ideas on how to lower the control pressure? I just removed both screens and took the whole thing apart. Should run full flow. It does not pass any fuel, even open in a bucket. How is this supposed to pass fuel? I can blow through the passages, reassemble and it still won't pass fuel. Beginning to suspect I have the wrong WUR. ANYTHING IS POSSIBLE with this one. Does the engine have to be running for the control pressure to come down? I certainly have not heard the engine run, I don't know how I would get it started, it just cranks and cranks.

[irarref215]

Ok so there is no way to delete or edit posts that I can find. I found a problem with the fuel pressure tester I was using. I will move forward. Sorry to bother anyone with my car nonsense. This one is getting really old. I am an EFI guy, this mechanical injection is not for me.

[Bitsyncmaster]

You check the primary pressure with the engine off, RPM relay jumpered and test valve closed. Your 68 PSI is typical primary pressure.

You check the control pressure with engine running and test valve open. I'm not sure what you would get with engine off.

Does your engine fire at all when you try to start it? Have you tried starter fluid?

[DMCVegas]

Injector volume was all over the place. Purchased 6X injectors. Still varied in volume. Had the fuel distributor rebuilt. .

Did you first swap injectors between fuel hoses to ensure that the variances followed the injectors before you had the distributor rebuilt?

[Ron]

Any ideas on how to lower the control pressure?

See http://dmctalk.org/showthread.php?1900-Wur
Be sure to read the whole thread first!

[irarref215]

Got the test fixture correct. I have 71 PSI with the valve closed and 42 PSI control pressure. When I attempt to start the thing, it fires, then sputters and dies. I am going to take the frequency valve off again and attempt to see if it is clean, but I have already done that.

@ DMCVEGAS The injectors were replaced and the flow messed up and would not follow an injector swap.

[irarref215]

Yes I did find some crud in the FV. Fished that out of there and the car seems to run good. 51 PSI control pressure when warm, 71 PSI total. It has a bit excessive leak down, but I am attributing that to a partially leaking accumulator. The only issue left is when I stop somewhere, park it for say, 2 to 20 minutes. The car will start and rev to 3000 RPM and run there for 5-7 seconds, and then return to idle, 900 RPM. What would cause this to rev so high on an immediate restart? I think it is related to the idle air control (oops! GM lingo). It is buzzing when running, and the resistance measurements are 10 ohms for each side, 20 ohms total. I moved the internal 'vane' and it seems to roll back and forth unobstructed. Could this be causing the starting RPM to soar for so long?

[Bitsyncmaster]

Yes I did find some crud in the FV. Fished that out of there and the car seems to run good. 51 PSI control pressure when warm, 71 PSI total. It has a bit excessive leak down, but I am attributing that to a partially leaking accumulator. The only issue left is when I stop somewhere, park it for say, 2 to 20 minutes. The car will start and rev to 3000 RPM and run there for 5-7 seconds, and then return to idle, 900 RPM. What would cause this to rev so high on an immediate restart? I think it is related to the idle air control (oops! GM lingo). It is buzzing when running, and the resistance measurements are 10 ohms for each side, 20 ohms total. I moved the internal 'vane' and it seems to roll back and forth unobstructed. Could this be causing the starting RPM to soar for so long?

Never heard of any others with that 3000 RPM restart problem. I would guess your idle ECU may have a problem. If you know another owner that would lend you his ECU you could verify it or not.

[irarref215]

Never heard of any others with that 3000 RPM restart problem. I would guess your idle ECU may have a problem. If you know another owner that would lend you his ECU you could verify it or not.

Thanks Dave. I was under the impression that it went fully open when started, then closed off for idle. I don't have anyone to swap parts with. Is there some measurements I can do to make sure it is right? I think what I will do first is start the vehicle with the ISM plugged in and get a stable idle. I will then unplug it , shut off the engine and try a restart and see if it jumps to 3000+ rpm. If it does then I most likely have another problem. Is this a good approach?

[Bitsyncmaster]

Thanks Dave. I was under the impression that it went fully open when started, then closed off for idle. I don't have anyone to swap parts with. Is there some measurements I can do to make sure it is right? I think what I will do first is start the vehicle with the ISM plugged in and get a stable idle. I will then unplug it , shut off the engine and try a restart and see if it jumps to 3000+ rpm. If it does then I most likely have another problem. Is this a good approach?

The stock ECU jumps to about half open on a cold engine on start up. With a warm engine it jumps less than half open depending on the engine temp sensor feeding the ECU.

You had said your idle is 900 RPM but the stock ECU sets 775 RPM. I'm guessing your curb idle screw is holding the idle to high which would also affect the start RPM.

Try to adjust to get that stock 775 RPM with a hot engine and see if that stops the 3000 RPM start up.

[irarref215]

The stock ECU jumps to about half open on a cold engine on start up. With a warm engine it jumps less than half open depending on the engine temp sensor feeding the ECU.

You had said your idle is 900 RPM but the stock ECU sets 775 RPM. I'm guessing your curb idle screw is holding the idle to high which would also affect the start RPM.

Try to adjust to get that stock 775 RPM with a hot engine and see if that stops the 3000 RPM start up.

Firstly, it does not rev like this if the ism is unplugged. It is for sure the thing that is opening causing the racing.

Hmmm. Engine temp sensor? OK I will for sure attempt to adjust the curb idle screw with a hot engine. I need to stick my tach/dwell meter on there to be more accurate as I was looking at the cluster rpm. I think I would like to test that temp sensor as well. I have done so much work to get to this point, it is going to be great to drive the car.

[irarref215]

Firstly, it does not rev like this if the ism is unplugged. It is for sure the thing that is opening causing the racing.

Hmmm. Engine temp sensor? OK I will for sure attempt to adjust the curb idle screw with a hot engine. I need to stick my tach/dwell meter on there to be more accurate as I was looking at the cluster rpm. I think I would like to test that temp sensor as well. I have done so much work to get to this point, it is going to be great to drive the car.

Looks like you all allowed someone to hijack my original post. I can't do that, why can this person? I still have this problem. I am still trying to figure out why this car revs to 3,500 RPM when started. OK now three years later. Going to have to try to fix this problem. What else can cause the engine to rev to 3,500 rpm on startup and then idle down after 10 seconds? There has to be a reason for this. Static fuel pressure is 70 psi, pre warm pressure is 40 and then rises to 50 when it is warm. I can't have the engine revving to 3,500 RPM every time I start it. Very hard on the engine. Anyone?

[Bitsyncmaster]

Looks like you all allowed someone to hijack my original post. I can't do that, why can this person? I still have this problem. I am still trying to figure out why this car revs to 3,500 RPM when started. OK now three years later. Going to have to try to fix this problem. What else can cause the engine to rev to 3,500 rpm on startup and then idle down after 10 seconds? There has to be a reason for this. Static fuel pressure is 70 psi, pre warm pressure is 40 and then rises to 50 when it is warm. I can't have the engine revving to 3,500 RPM every time I start it. Very hard on the engine. Anyone?

I would try another idle ECU if you can borrow one.

You can also short the temp sensor wires at the idle ECU just to verify if that will fix the problem. Those are the black/yellow to black/slate wires.

[David T]

Check the decel springs on the throttle butterfly plates. Check the adjustments on the throttle arm making sure the throttle moves freely and returns all the way back to the idle position by itself.

[SBL]

I bet that it is the idle ECU. If you unplug the ISM, I assume that it will start and not rev up to 3000. This means that either a) the ISM is getting incorrect information from the ECU, or b) the idle ECU is feeding correct information to the ISM but the ISM is not working well (sticky). A final possibility is that there is a vac leak somewhere and the idle ECU and ISM are "trying their best" to compensate and it takes 20 sec or so.

In the forum I found a person who had this problem in Brazil, and I had this problem as well. After checking everything, by process of elimination I blamed the idle ECU. $138 later (one of Dave's units), perfect starts and idles, and no initial high idle. Trust me, even if it is not the culprit, the options available to program via DIP switches make this a useful investment anyway.

I agree it is not good for the engine. While waiting for your idle ECU, or whatever you plan to do, drive without the ISM connected, using brass screws or curb idle screw to keep idle somewhat close to being acceptable on a temporary basis. It will not hurt anything. Do the final unplugging of the ISM after you start it with it plugged in, and it settles down. Then unplug it. There is no guarantee that the ISM position will remain in that position due to vibration, but it is a good place to start.

[irarref215]

I bet that it is the idle ECU. If you unplug the ISM, I assume that it will start and not rev up to 3000. This means that either a) the ISM is getting incorrect information from the ECU, or b) the idle ECU is feeding correct information to the ISM but the ISM is not working well (sticky). A final possibility is that there is a vac leak somewhere and the idle ECU and ISM are "trying their best" to compensate and it takes 20 sec or so.

In the forum I found a person who had this problem in Brazil, and I had this problem as well. After checking everything, by process of elimination I blamed the idle ECU. $138 later (one of Dave's units), perfect starts and idles, and no initial high idle. Trust me, even if it is not the culprit, the options available to program via DIP switches make this a useful investment anyway.

I agree it is not good for the engine. While waiting for your idle ECU, or whatever you plan to do, drive without the ISM connected, using brass screws or curb idle screw to keep idle somewhat close to being acceptable on a temporary basis. It will not hurt anything. Do the final unplugging of the ISM after you start it with it plugged in, and it settles down. Then unplug it. There is no guarantee that the ISM position will remain in that position due to vibration, but it is a good place to start.

Great. Thank you for all your good advice. I think I will see if the thermistor is working via measuring at the idle ECU. Have fixed many things the PO did. Missing gaskets, things plugged in to where they don't belong, misadjusted screws etc. This guy did 7+ years of screwing with it. I am still not sure it ever ran right, because when I got it on a flatbed trailer, it barely ran.

[irarref215]

I would try another idle ECU if you can borrow one.

You can also short the temp sensor wires at the idle ECU just to verify if that will fix the problem. Those are the black/yellow to black/slate wires.

So if I read the workshop manual correctly, it states, "A thermistor (3), located in the coolant system distribution pipe, will activate another circuit within the ECU module when the coolant temperature is below 15deg C. This circuit will provide a fast idle condition". So am I correct in thinking that the thermistor (actually a temp switch, huh?) opens when the temp gets too low and then closes above 15 deg C?

[Bitsyncmaster]

So if I read the workshop manual correctly, it states, "A thermistor (3), located in the coolant system distribution pipe, will activate another circuit within the ECU module when the coolant temperature is below 15deg C. This circuit will provide a fast idle condition". So am I correct in thinking that the thermistor (actually a temp switch, huh?) opens when the temp gets too low and then closes above 15 deg C?

The idle ECU uses a thermistor which varies resistance as temperature changes. It's about 40 Kohms cold and 1 Kohms hot and the resistance varies between those values as it warms up. What that does to the stock idle ECU is limit how far closed the idle motor will close. That can result in a faster idle RPM but depends on other adjustments of the throttle. It does not set a different closed loop RPM control in the ECU.

Now the lambda "thermal throttle enrichment" is a temperature switch.

[irarref215]

The idle ECU uses a thermistor which varies resistance as temperature changes. It's about 40 Kohms cold and 1 Kohms hot and the resistance varies between those values as it warms up. What that does to the stock idle ECU is limit how far closed the idle motor will close. That can result in a faster idle RPM but depends on other adjustments of the throttle. It does not set a different closed loop RPM control in the ECU.

Now the lambda "thermal throttle enrichment" is a temperature switch.

OK I see that. Room temp it is about 9K ohms. I think that is about right from what I see. I opened up the ECU and didn't see anything obvious. Tested some of the active components and some resistors and everything looks good there. Going to take the cold start valve off and look into the ISM and do a key cycle to see what it is doing. Looks like the inputs to the ECU (Tach, thermisor, idle switch) are good testing at the ECU. Too bad I don't know anyone with a delorean that will let me use their ECU. Anyone have a 'loaner' out there I can use? Meanwhile, I will insure the ISM is free and operational again.

[Bitsyncmaster]

OK I see that. Room temp it is about 9K ohms. I think that is about right from what I see. I opened up the ECU and didn't see anything obvious. Tested some of the active components and some resistors and everything looks good there. Going to take the cold start valve off and look into the ISM and do a key cycle to see what it is doing. Looks like the inputs to the ECU (Tach, thermisor, idle switch) are good testing at the ECU. Too bad I don't know anyone with a delorean that will let me use their ECU. Anyone have a 'loaner' out there I can use? Meanwhile, I will insure the ISM is free and operational again.

The most common failure of the OEM idle ECU is a bad driver transistor but that is indicated by no buzzing of the idle motor.

[irarref215]

The most common failure of the OEM idle ECU is a bad driver transistor but that is indicated by no buzzing of the idle motor.

The ISM does vibrate. I power cycled the ignition while looking at the ISM, and it fully opens, then slowly closes till it is a 1/16" gap. I measured the voltage at the ISM, it was 9 volts. I am sure I have tested this before in the three years I have been working on this problem and it was 12V. Power to the idle ECU was at 10V. Found fuse #1 had some corrosion dropping voltage. Got the ISM at 12V now. Going to drop the oil, it is diluted then attempt to run the engine again. Pretty sure it I am down to only the IDLE ECU/ISM. Any more advice, I am open to suggestions.

[Bitsyncmaster]

The ISM does vibrate. I power cycled the ignition while looking at the ISM, and it fully opens, then slowly closes till it is a 1/16" gap. I measured the voltage at the ISM, it was 9 volts. I am sure I have tested this before in the three years I have been working on this problem and it was 12V. Power to the idle ECU was at 10V. Found fuse #1 had some corrosion dropping voltage. Got the ISM at 12V now. Going to drop the oil, it is diluted then attempt to run the engine again. Pretty sure it I am down to only the IDLE ECU/ISM. Any more advice, I am open to suggestions.

When measuring the voltage on the ISM your measuring the average voltage. It is really a 100 Hz. switching of the 12 volts square wave switching to 0 volts. The other side of the ISM has the reverse duty cycle to that average would read different. The center terminal of the ISM is the 12 volts and the side terminals get switched to ground (square wave) by the ECU.

[irarref215]

When measuring the voltage on the ISM your measuring the average voltage. It is really a 100 Hz. switching of the 12 volts square wave switching to 0 volts. The other side of the ISM has the reverse duty cycle to that average would read different. The center terminal of the ISM is the 12 volts and the side terminals get switched to ground (square wave) by the ECU.

I get that the outer terminals are going to be an average because of the 100 hz square wave. The center post (+12V) was low because of the corrosion. Going to fire this up again soon and see if anything changed. I fixed a few small things, but the fuse that I found the corrosion on powers the coil, RPM relay and this Idle ECU. Not sure what to do other than unplugging the ISM to keep the idle down when starting. Not going to throw money at an idle ECU for $200 or an ISM for $???. I don't shotgun. Three years later... still didn't fix it!

[irarref215]

I get that the outer terminals are going to be an average because of the 100 hz square wave. The center post (+12V) was low because of the corrosion. Going to fire this up again soon and see if anything changed. I fixed a few small things, but the fuse that I found the corrosion on powers the coil, RPM relay and this Idle ECU. Not sure what to do other than unplugging the ISM to keep the idle down when starting. Not going to throw money at an idle ECU for $200 or an ISM for $???. I don't shotgun. Three years later... still didn't fix it!

Still revs to 3000-4000 rpm immediately after it starts. I just unplugged the idle ECU and the problem stops. When I look down the throat of the ISM when the key cycles, it opens all the way and then takes several seconds to return to a little slit. Why would the car do anything else other than overspeed right after start? Is this the way all of the Delorean ISM's operate? I tool a look at another video from someone here:

https://www.youtube.com/watch?v=fUOK0ksB0Gs

That is clearly not what mine does, my ISM opens all the way, then slowly closes. This video shows the ISM starting closed, then slowly opening, then slowly closing. Is there anyone repairing the idle ECU's anymore? Does anyone have a schematic for it?