Hot start issue. What next?

[SShaw]

So I have been having a hot/warm start issue. After I drive it long enough to get up to temperature and letting it sit for more than about 30 minutes it will have trouble starting. Once it sits long enough it's fine. I believe I am losing pressure. I have replaced the accumulator, check valve and PPR O-Rings. I also double checked the torque on the banjo bolts at the distributor. Any suggestions on where to look next? Attached is some data if it interests you.

50097

[David T]

Does it start right up when you do a plug swap? If so you need to figure out why you are losing rest pressure. With all of the stuff you replaced, now it could be anything.

[Bitsyncmaster]

Test how long you hold rest pressure. It is best to have a pressure gauge but you can do it without one. Remove the air cleaner, start your engine and run it for a few seconds then shut it down. Now lightly tap with your finger on the air plate and the rest pressure should keep it from moving. Don't press hard enough to move the air plate or that will cause the injectors to spray. Now time and repeat that "tap test" until that air plate moves freely. When it moves freely you have lost rest pressure.

In the hot summer, I found I had to hold rest pressure for greater than 3 hours or I would have warm start issues if I tried to start it 3.5 hours after shut down. Engine would cool enought after 4 hours and start fine.

[Some guy]

I had all the same issues. I replaced everything i could think of and find. Nothing worked for me.

I ended up making a switch that jumpers the cold stat valve. I wired it from the fuse box terminal to a switch by my shifter.

i know it is not the right fix, but it works. I know someone made a relay that has a delay fire that dose the same thing, but i like having the control over it.

[SShaw]

I just did the CSV plug swap and it didn't start up right away. It sputtered, started and died. I then removed the CSV, put it in a cup, did the RPM relay jumpers and it does spray fuel. Ideas?

[SShaw]

It held rest pressure at the plate for between 1.5 and 2 hours. Since I was having the issue after 30min is it safe to assume it's related to the CSV?

[David T]

It is possible it is not fuel related. It could be some problem with ignition that is somehow affected by heat. If the plug swap didn't help you need to see if you have spark.

[kings1527]

So I have been having a hot/warm start issue. After I drive it long enough to get up to temperature and letting it sit for more than about 30 minutes it will have trouble starting. Once it sits long enough it's fine. I believe I am losing pressure. I have replaced the accumulator, check valve and PPR O-Rings. I also double checked the torque on the banjo bolts at the distributor. Any suggestions on where to look next? Attached is some data if it interests you.

50097

Everything you listed as replaced are the only things involved in maintaining rest pressure in the system per the K-Jet design. I think you have a problem elsewhere that's not related to rest pressure if everything you replaced was done correctly.

[SShaw]

Any suggestions of what to test next? Once it starts it runs great. Is there anything ignition wise that could be affected by heat?

[David T]

Any suggestions of what to test next? Once it starts it runs great. Is there anything ignition wise that could be affected by heat?

Reread post #7 last part.

[SShaw]

So I haven't tested spark but in the last year I have replaced the battery, ignition coil, rotor, cap, wires and plugs.

I've noticed a few more symptoms that may be related. A few times I've had high idle when warm and in park. On occasion it will also start slow when cold. Even start and die. But it will always start without too much trouble within two attempts. Leaking injector maybe?

[madstudios]

So I haven't tested spark but in the last year I have replaced the battery, ignition coil, rotor, cap, wires and plugs.

I've noticed a few more symptoms that may be related. A few times I've had high idle when warm and in park. On occasion it will also start slow when cold. Even start and die. But it will always start without too much trouble within two attempts. Leaking injector maybe?

Did you ever adjust your mixture with a Dwell Meter?
I found out mine was with a very rich mixture, and after the adjustment now starts a lot better when warm or hot! Very occasionally I have hot start issues, usually I have to crank the engine 2 or 3 times when it happens, and I'm good to go.
Yesterday I also bought a hot start relay from Dave, just in case... I'll test as soon as I get it.


Fernando Silotto. Sao Paulo - Brazil
Delorean Vin 3772

[SShaw]

I finally got around to checking the dwell. It's bouncing around 35 (70 once doubled) which is too high. It should be around 25 (50), correct? Is it safe to assume that means it's running too rich?


https://www.youtube.com/watch?v=V-WPKeHVG8M

[Bitsyncmaster]

I finally got around to checking the dwell. It's bouncing around 35 (70 once doubled) which is too high. It should be around 25 (50), correct? Is it safe to assume that means it's running too rich?


https://www.youtube.com/watch?v=V-WPKeHVG8M

Even with it running 70 deg dwell, the lambda system is still holding AFR where it should at 14.7.

It's just that that maladjusted dwell will make the cold engine run at the wrong mixture and if you hit wide open throttle your AFR will go a little lean.

[SShaw]

Even with it running 70 deg dwell, the lambda system is still holding AFR where it should at 14.7.

It's just that that maladjusted dwell will make the cold engine run at the wrong mixture and if you hit wide open throttle your AFR will go a little lean.

But I should go ahead and adjust it so it's in the 40-50 range even if it's unrelated to my warm start issue?

[Bitsyncmaster]

But I should go ahead and adjust it so it's in the 40-50 range even if it's unrelated to my warm start issue?

Yes, I would set it to the book value. It still may cure your warm starting issue.

[David T]

You should not be adjusting the mixture screw until you have EVERYTHING else well sorted out and operating as it should. No amount of adjustment can compensate for things not working correctly. That includes vacuum leaks, worn spark plugs, bad wires, leaky valves, dirty injectors, stale fuel, etc.

[SShaw]

Thanks for the help guys! I am fairly confident everything else is in good shape so I adjusted the mixture with the dwell meter. It wasn't giving me a great reading, I don't think the engine was warm enough, and I made it a little lean. A few days later I did it again and dialed it in just right. This appears to have to have resolved my hot start issue! The only lingering issue I see is that on occasion it will idle a bit high when warm and in Park. As soon as I put it in Reverse or Drive it idles just fine. Any ideas? Data attached.

51445