Hot Start Issue

[rothsean]

Hello all. I have recently replaced my fuel pump, accumulator and fuel filter. I still have a hot start issue that is kinda strange.

If I turn the engine on within 5 minutes of shutting down it fires right up. Around 20 minutes or so after shutting down, in order to starte, I have to turn the started for about 10 seconds then it finally picks up.

Any ideas? Any troubleshooting or diagnosing ideas?

Thanks!

[Mike C.]

Have you checked ur Primary Pressure O-Ring?

[rothsean]

Have you checked ur Primary Pressure O-Ring?

No where is that? What do I look for when checking it? What does it do?

[DeLorean03]

Pictures and explanation courtesy of John Hervey at SpecialTAuto:


12945


12944

The PPR that Mike mentioned is in the fuel distributor - as an accessible area on the side where you can change out the O-Rings.

[Rich]

....20 minutes or so after shutting down, in order to start, I have to turn the started for about 10 seconds then it finally picks up.

Troubleshooting test:

Repeat the problem situation you describe, except interrupt the starting procedure by holding the key in the ON position for 5-10 seconds before START. This allows the fuel pump to build pressure in case your (new) accumulator or some other element is acting up or leaking down. This will largely rule out low fuel pressure at the front end of the K-Jet system, assuming your pump is good. If the car starts right up in this case then the problem is upstream of the fuel metering hardware. If it still takes 10sec to start then its in the metering/controls. Or the ignition...

Am assuming you prefer not to use or cannot find your way to a decent Bosch-friendly auto repair facility. They can often zero in on such problems within an hour with a gauge set and experience. Looks as if 3 parts already were replaced in your quest; a shop diagnosis might minimize further parts-chases. Good luck in any case.

[Mike C.]

No where is that? What do I look for when checking it? What does it do?

Im sorry I didn't post a link! I was checking in on my phone. Thanks for posting the pics and link, Jeremiah! I owe you a "high five of awesomeness" :thumbup2:

[rothsean]

Troubleshooting test:

Repeat the problem situation you describe, except interrupt the starting procedure by holding the key in the ON position for 5-10 seconds before START. This allows the fuel pump to build pressure in case your (new) accumulator or some other element is acting up or leaking down. This will largely rule out low fuel pressure at the front end of the K-Jet system, assuming your pump is good. If the car starts right up in this case then the problem is upstream of the fuel metering hardware. If it still takes 10sec to start then its in the metering/controls. Or the ignition...

Am assuming you prefer not to use or cannot find your way to a decent Bosch-friendly auto repair facility. They can often zero in on such problems within an hour with a gauge set and experience. Looks as if 3 parts already were replaced in your quest; a shop diagnosis might minimize further parts-chases. Good luck in any case.


I tried the fue pump trick as explained above, it did not change the hot start issue that I have.

[rothsean]

Pictures and explanation courtesy of John Hervey at SpecialTAuto:


12945


12944

The PPR that Mike mentioned is in the fuel distributor - as an accessible area on the side where you can change out the O-Rings.

Is this a DeLorean specific part or can I get it elsewhere?

[DeLorean03]

Is this a DeLorean specific part or can I get it elsewhere?

I would say yes and no. Obviously, the DeLorean uses a specific fuel distributor. The one picture is not the only one that Bosch makes - so yes it is DeLorean specific in that the car uses 1 unit of multiple different kinds.

Basically, just purchase the primary pressure O-rings from John Hervey. Your fuel distributor should not need replacing. The O-rings are specific to a hot start problem - do NOT go spending $400+ dollars on a new FD - just buy the $3.50 O-rings over at SpecialTAuto's fuel parts page:

12956

[DeLorean03]

Im sorry I didn't post a link! I was checking in on my phone. Thanks for posting the pics and link, Jeremiah! I owe you a "high five of awesomeness" :thumbup2:

Even the mods need a lil' help from time to time ;).

[rothsean]

I would say yes and no. Obviously, the DeLorean uses a specific fuel distributor. The one picture is not the only one that Bosch makes - so yes it is DeLorean specific in that the car uses 1 unit of multiple different kinds.

Basically, just purchase the primary pressure O-rings from John Hervey. Your fuel distributor should not need replacing. The O-rings are specific to a hot start problem - do NOT go spending $400+ dollars on a new FD - just buy the $3.50 O-rings over at SpecialTAuto's fuel parts page:

12956

Thanks, I just ordered the O-ring kit from SpecialT. Where do all three of the o-rings go? All on the same bolt piece in the fuel distributor?

[Chris4099]

When you remove the "bolt", there will be a spring and some shims. Don't lose those shims!!! The larger o-ring and copper washer go on this (both included in the kit). Chances are the plunger will still be inside the distributor. Take a paper clip and straighten it out. Now bend the tip into a small 90 degree hook. This will allow you to stick it inside the distributor and pull out the plunger (it's hollow inside, so you should be able to hook it). You then replace the small o-ring and reinsert everything back together.

Another pic from their site showing all these parts:
http://specialtauto.com/delorean-parts/images/Prim-press-regulator-1.jpg

[David T]

Check the TTS and the CSV for proper operation. After 20 minutes you have lost enough rest pressure for the problem to not be a rest pressure problem. Don't mess with "O" rings. You will cause more problems than you will fix. If you do have a problem with Rest Pressure after replacing the accumulator it may be the check valve on the fuel pump or a fuel leak.
David Teitelbaum

[rothsean]

Check the TTS and the CSV for proper operation. After 20 minutes you have lost enough rest pressure for the problem to not be a rest pressure problem. Don't mess with "O" rings. You will cause more problems than you will fix. If you do have a problem with Rest Pressure after replacing the accumulator it may be the check valve on the fuel pump or a fuel leak.
David Teitelbaum

Ok, it should not be the pump, I just installed the new all-in-one fuel pump unit from DMCH 2 weeks ago. My car starts up fine within 5-10 minutes of shutting down, so you are saying that my o-rings are most likely fine?

As far as a fuel leak, I have searched everywhere for dripping fuel and can't find any. Is there a better way to test for a leak?

[David T]

Your nose is the best instrument to know if there is a leak but it won't find the exact source. I am not familiar enough with the new fuel pump set-up to help you there. You *could* have a problem with it leaking back and losing your rest pressure but as I said, rest pressure is not the problem. I suspect it the the Cold Start Valve system. See if the CSV is passing fuel on start up. Try it on a cold motor first. Even if it does work on a cold motor it may not work on a warm motor if the TTS is bad. At least if you see it working cold you know the CSV and the wiring is OK. Other systems that are active during start-up include the resistor bypass relay, the CPR and the vacuum advance. All should be verified for proper operation. If you need a tune-up that can also cause difficulty starting (worn plugs, wires).
David Teitelbaum

[rothsean]

Your nose is the best instrument to know if there is a leak but it won't find the exact source. I am not familiar enough with the new fuel pump set-up to help you there. You *could* have a problem with it leaking back and losing your rest pressure but as I said, rest pressure is not the problem. I suspect it the the Cold Start Valve system. See if the CSV is passing fuel on start up. Try it on a cold motor first. Even if it does work on a cold motor it may not work on a warm motor if the TTS is bad. At least if you see it working cold you know the CSV and the wiring is OK. Other systems that are active during start-up include the resistor bypass relay, the CPR and the vacuum advance. All should be verified for proper operation. If you need a tune-up that can also cause difficulty starting (worn plugs, wires).
David Teitelbaum


What is TTS?

[DeLorean03]

ThermoTimeSwitch...

Remember everyone - spell out the words so people that haven't been around that long know what you're talking about.

[David T]

The TTS (Thermal Time Switch) runs the CSV (Cold Start Valve) during cranking but only if it is cold and only for a few seconds to avoid flooding the motor. If it is not operating correctly (assuming the wiring is OK) it may not work when it is supposed to or it could work when it is not supposed to. My guess as to why they fail is if you force the plug on the wrong way or you f-ck up the wiring you damage the switch's internals. I have also seen one installed with so much teflon tape it could not ground itself. Very rare to see the CSV not work. I did find one once where the "O" ring was missing and it leaked vacuum. The CPR (Control Pressure Regulator) aka warm-up regulator, varies the control pressure on the mixture unit. If it is not calibrated correctly or the wiring inside is burnt up it will not change the control pressure as it should and you will have drivability problems till the motor warms all the way up. There are a LOT of systems to deal with start-up and warm-up and if they are not all working as they should any of them can cause problems.
David Teitelbaum