General starting problem (hot or cold)

[DMC3165]

Hi all. For the past several months I've been having a general starting problem with my car. It idles low and sounds lumpy like it has a miss but it always goes away after a few minutes and idles normal once it reaches operating temperature. It seems to be worse if the car was parked for an hour or two. If it stalls on a warm restart I have to let it sit for a minute otherwise it'll crank but won't run.

Earlier this year I had a weak fuel pump fail. I might be jumping to conclusions but I'm wondering if the weak pump damaged something in the fuel system? A check valve somewhere?

Occasionally it'll start fine but always when cold. When it's warm I have to nurse the throttle a little just to keep it above 500 rpms. But after running for a minute or two it's just fine. For now it's more of a nuisance problem but I'm sure it's going to get worse.

Any thoughts?

[Rich]

....Earlier this year I had a weak fuel pump fail. I might be jumping to conclusions but I'm wondering if the weak pump damaged something in the fuel system? A check valve somewhere?

Setting aside your specific questions about starting and idling to ask for more info and offer a side answer.

Question: Are you saying that you replaced the fuel pump earlier this year? Which brand/supplier pump is in there now? It may have something to do with the starting problem.

Side answer: Very unlikely that the weak pump damaged anything. Set that worry aside for now.

[David T]

Setting aside your specific questions about starting and idling to ask for more info and offer a side answer.

Question: Are you saying that you replaced the fuel pump earlier this year? Which brand/supplier pump is in there now? It may have something to do with the starting problem.

Side answer: Very unlikely that the weak pump damaged anything. Set that worry aside for now.

Since it is very common, I would check for vacuum leaks. It also seems as if your ignition system may need some new parts. Other possibilities include dirty injectors with a bad pattern. Unlikely it has anything to do with your fuel pump.

[sdg3205]

Sounds like a fuel pressure problem. Have you thrown some gauges on it?

If you've got rest pressure and a hot start problem, id check the CSV isnt firing at hot start and the WUR isnt throwing out your fuel pressure. If both were doing weird things my guess is it would be the thermistor on the y-pipe is toast.

Just a guess!

[DMC3165]

I think it may be something related to ambient temperature. It generally starts better in cooler weather when it hasn't been run for about 10-12 hours.

[Bitsyncmaster]

I think it may be something related to ambient temperature. It generally starts better in cooler weather when it hasn't been run for about 10-12 hours.

That is a sign of your mixture is too rich when starting. Have you adjusted the mixture? You can also unplug the CSV to see if that helps your warmer starts.

[kings1527]

Sounds like a fuel pressure problem. Have you thrown some gauges on it?

If you've got rest pressure and a hot start problem, id check the CSV isnt firing at hot start and the WUR isnt throwing out your fuel pressure. If both were doing weird things my guess is it would be the thermistor on the y-pipe is toast.

Just a guess!

That's exactly what I was going to say. This was the EXACT same problem I was having with my hot start issue and it turned out to be my PPR o-ring. I had every symptom you just mentioned in the OP. My old o-ring was probably Buna-N and it swelled up over a period of time due to the ethanol in today's fuel and couldn't seal anymore. I replaced it and it's as good as new, now. Hot or cold starts.

I'd definitely go through and troubleshoot your all of your common rest pressure parts (PPR O-rings, accumulator, and fuel pump check valve).

[David T]

That is a sign of your mixture is too rich when starting. Have you adjusted the mixture? You can also unplug the CSV to see if that helps your warmer starts.

Not necessarily. If it starts well when it is cold the Cold Start Valve is running during cranking and starts it right up. If it is warm-hot the CSV doesn't operate and that is when it is harder to start. That would lead me to believe that it is too LEAN when you are having trouble starting. Could be the CPR or a problem with Rest Pressure. One way to test this theory is to do the plug swap or a squirt of Ether when it is hard to start. That would confirm a fuel problem as opposed to an ignition problem.

[DeLorean03]

I cannot stress this enough:

http://www.amazon.com/CTA-Tools-3420-Jetronic-Injection/dp/B008FJXA3M

Ownership of these gauges need to be a requirement before buying a DeLorean. I went years guessing on symptoms, trying to figure these kinds of things out, and buying these gauges was one of the best things I've ever done.

And I promise, I'm not trying to blast the OP. I only post this because these gauges pay for themselves in one use. They provide a "baseline" for what could be going wrong, and in some cases, they eliminate the fuel system altogether, allowing for the owner to focus on other areas of the car.

Look at the Amazon link, it even has a picture of the gauges on the hood of a DeLorean. That says it all :thankyou:.

[DMC3165]

When this issue first started in the spring. I was stranded on the side of the road. On a warm restart it had a low missing idle of about 500. I went to pull away and the car died. It would not restart on it's own. I bought a can of starting fluid and the car fired right up but with the low idle until it warmed up. Brought it to one of the local vendors who did some work on it but the problem remained. A few months later my fuel pump quit. This was due to disintegrated rubber getting in the tank from somewhere and clogging the pickup screen. Eventually the restricted pump overheated and quit (small side note to this rubber had been building up for a few years I'm still not sure where it came from). I put in a new screen, installed a new pump and I was back on the road but still with the low idldling at startup. After two additiaonl attempts to solve the problem it still persists for the better part of this year. About a month ago I took my wife out for dinner and after we ate (2 hours or so) We got back in the car started it, went to pull away and it stalled again and would not restart. I let it sit for about 5 minutes and it finally restarted.

I noticed something tonight I hadn't before. If I run the engine warm it up, shut it and restart it under 5 seconds evrything is completely normal. Could this be a sign of a bad WUR/CPR? Mine is either origninal or 15 years old beacuse I've never replaced it. Also the plug connectors on my CSV and CPR are not in the best of shape. Both are showing signs of corrosion and the CSV connector has one slot either burnt or overheated.

On the advice of a few different people I have ordered new plugs for both, a new CPR and PPR O-ring kit. Fingers crossed this works!

[DMCMW Dave]

Look at the Amazon link, it even has a picture of the gauges on the hood of a DeLorean. That says it all :thankyou:.

Did you do that? :hysterical:

[DeLorean03]

Did you do that? :hysterical:

I sure wish I could claim credit for it. I really do :D.

Those gauges, back in 2004, were about $55 or so. When I bought mine just this year, they were $89 for the first pair and $110 for the second pair. Now, they're inching up to $150.

They're super-easy to use, and they can tell you a lot about what may or may not be going on with the car. Just this year alone, they helped Dave and me figure out that my check valve was bad and also helped me realize that I did not need to buy a CPR when I thought that was what I needed for sure.

I stress this because I am easily spooked by using equipment from the 1980's. These gauges are an absolute synch (sp?) to use. Well worth the time and money spent.

[refugeefromcalif]

I cannot stress this enough:

http://www.amazon.com/CTA-Tools-3420-Jetronic-Injection/dp/B008FJXA3M

Ownership of these gauges need to be a requirement before buying a DeLorean. I went years guessing on symptoms, trying to figure these kinds of things out, and buying these gauges was one of the best things I've ever done.
Look at the Amazon link, it even has a picture of the gauges on the hood of a DeLorean. That says it all :thankyou:.

Thanks again for the link. My gauges will be here tomorrow.

George

[DeLorean03]

Thanks again for the link. My gauges will be here tomorrow.

George

Glad to help bud - you won't regret snagging a set when you REALLY need them :thumbup: !

[rdarlington]

I cannot stress this enough:

http://www.amazon.com/CTA-Tools-3420-Jetronic-Injection/dp/B008FJXA3M

<snip>

Look at the Amazon link, it even has a picture of the gauges on the hood of a DeLorean. That says it all :thankyou:.

Hahah, that's my car in the picture. :-)

While I agree they CAN pay for themselves in one use, make sure you have a supply of copper gaskets ahead of time so that you're not stuck when you drop one down on top of the distributor (ignition distributor) and then it slides under the manifold. If you see mine, please look around for that 11mm socket I managed to sacrifice to the engine gods down there too.

-Bob

[rdarlington]

<snip>

I noticed something tonight I hadn't before. If I run the engine warm it up, shut it and restart it under 5 seconds evrything is completely normal. Could this be a sign of a bad WUR/CPR? Mine is either origninal or 15 years old beacuse I've never replaced it. Also the plug connectors on my CSV and CPR are not in the best of shape. Both are showing signs of corrosion and the CSV connector has one slot either burnt or overheated.

<snip>



No, this problem can't be a CPR/WUR problem if it does it when the engine is warmed up. Under the manifold lives the thermal control valve. When the engine is cold, vacuum runs to the control pressure regulator. When warm, that whole system is cut out and vacuum is then switched over to the vacuum advance line on the distributor.

-Bob

[DeLorean03]

Hahah, that's my car in the picture. :-)


-Bob

You are the man, dude. Love it!

Yes, extra washers are DEFINITELY a good call. I have - man - I think nearly 60 of them. At one point, Julee actually told me I cleaned them out of their inventory (yep, that's what happenes when you take off the FD/mixture unit 5 times in 1/2 a year).

Won't ever have to do that again soon ;) ....

[DMC3165]

Just to follow up with this. Installed new CPR and PPR o-rings and still the same problem persists. It does seem to run better under general operating conditions but definitely did not solve the problem I was trying to.

[Ron]

No, this problem can't be a CPR/WUR problem if it does it when the engine is warmed up. Under the manifold lives the thermal control valve. When the engine is cold, vacuum runs to the control pressure regulator. When warm, that whole system is cut out and vacuum is then switched over to the vacuum advance line on the distributor.

-Bob
Actually, it's not entirely cut out -- When the engine is above 40°C, the WUR/CPR must maintain 3.4 to 3.8 Bar...

[Bitsyncmaster]

Actually, it's not entirely cut out -- When the engine is above 40°C, the WUR/CPR must maintain 3.4 to 3.8 Bar...

+1
The WUR starts a very low control pressure (about 20 PSI) cold and eventually gets up to about 50 PSI hot. If the WUR is plugged you will see 70 PSI for control pressure.

[DMC3165]

Changed fuel filter today. Still no difference. On the advice of a few others I started searching for vacum leaks. Using starting fluid I lightly sprayed around a few vacum lines with no results. But the engine raced slightly when I sprayed the lower intake manifold near the passanger side head. I believe it maybe a cracked intake manifold gasket. Which would surprise me because they are only 2 years old.I think it maybe part of the problem if not the main problem. If it's a pinhole leak it makes sense it would be worse when cold. Maybe it swells up enough to seal as it warms up? Just guessing here.

[Bitsyncmaster]

Changed fuel filter today. Still no difference. On the advice of a few others I started searching for vacum leaks. Using starting fluid I lightly sprayed around a few vacum lines with no results. But the engine raced slightly when I sprayed the lower intake manifold near the passanger side head. I believe it maybe a cracked intake manifold gasket. Which would surprise me because they are only 2 years old.I think it maybe part of the problem if not the main problem. If it's a pinhole leak it makes sense it would be worse when cold. Maybe it swells up enough to seal as it warms up? Just guessing here.

Don't you mean O-rings for the intake seal? Would not think they would change unless you moved the intake. Check that the bolts are tight. Could also be an injector seal leaking.

[DMC3165]

Don't you mean O-rings for the intake seal? Would not think they would change unless you moved the intake. Check that the bolts are tight. Could also be an injector seal leaking.

Forgive me. It's a mistake in terminology. Bolts are tight and I haven't disturbed the manifold. However the injector seals are very old. At least 15 years or older. I'll have to look into this a little further.

[David T]

Forgive me. It's a mistake in terminology. Bolts are tight and I haven't disturbed the manifold. However the injector seals are very old. At least 15 years or older. I'll have to look into this a little further.

Very common for the injector seals to leak. They get old and hard and do not seal well. Each and every leak is additive, ie, each tiny leak adds to others till the net result is a leaning of the mixture. And it is not even. Some cylinders may be much leaner than others depending on where the leaks are. Another common but hard to see leak is the "O" ring seal for the idle motor pipe under the mixture unit. Vacuum leaks are invisible. It is difficult and dangerous to find them unless you use smoke machine. If you pull the injectors to replace the seals you should also have them tested and cleaned.

[DMC3165]

Very common for the injector seals to leak. They get old and hard and do not seal well. Each and every leak is additive, ie, each tiny leak adds to others till the net result is a leaning of the mixture. And it is not even. Some cylinders may be much leaner than others depending on where the leaks are. Another common but hard to see leak is the "O" ring seal for the idle motor pipe under the mixture unit. Vacuum leaks are invisible. It is difficult and dangerous to find them unless you use smoke machine. If you pull the injectors to replace the seals you should also have them tested and cleaned.

Looked at this closer today. Pulled 3 injectors on the right bank and all the seals looked ok. They looked old and a little dry but no obvious signs of damage (craks or breaks). I believe the leak may be under the intake manifold and it looks like it may be exactly what you said David. The idle jumped up when I sprayed ether under the intake on both sides in the general area of the idle motor pipe. I was thinking it may be the o-ring seal there as well. Not really sure if I feel comfortable with pulling the intake apart myself for a "possible" leak there. Plus I hear installing that o-ring is a royal PITA!

[rdarlington]

Actually, it's not entirely cut out -- When the engine is above 40°C, the WUR/CPR must maintain 3.4 to 3.8 Bar...

I meant from a vacuum pressure perspective. The WUR is still in play, but the vacuum (I believe) is switched over completely to the vacuum advance on the ignition distributor.

Do I have this wrong? I need to update my notes if so.

-Bob

[Ron]

I meant from a vacuum pressure perspective. The WUR is still in play, but the vacuum (I believe) is switched over completely to the vacuum advance on the ignition distributor.

Do I have this wrong? I need to update my notes if so.

-BobHey Bob,
Actually it completely switches its vacuum to the solenoid valve, which is connected to the vacuum advance on the ignition distributor... (I think you knew that ;-)

Anyway, I only mentioned it because he asked if it could be a sign of a bad WUR/CPR and you said, "No.....that whole system is cut out and vacuum is...." But it can, so I tried to explain how/why, just in case...
I pulled hair for days over one screwed up similar to what Bitsy mentioned (actually at its FD return oport)...ONCE. lol

[Ron]

Looked at this closer today. Pulled 3 injectors on the right bank and all the seals looked ok. They looked old and a little dry but no obvious signs of damage (craks or breaks). I believe the leak may be under the intake manifold and it looks like it may be exactly what you said David. The idle jumped up when I sprayed ether under the intake on both sides in the general area of the idle motor pipe. I was thinking it may be the o-ring seal there as well. Not really sure if I feel comfortable with pulling the intake apart myself for a "possible" leak there. Plus I hear installing that o-ring is a royal PITA!
This sounds like a perfect candidate for the cigar smoke test (before disassembly ;-)