Heat soak starting problems
Thread Starter
Joined: Oct 2004
Posts: 5,121
Likes: 74
From: somewhere in TX
Heat soak starting problems A friend of mine has a 98 ls1. On cold start it will spin about 3 or 4 seconds and start. Usually after sitting about twenty minutes it will crank anywhere from 13 to twenty seconds. After startup it has black smoke out of both duals. The only mods are a lid kooks headers and true duals. The tuning is stock and it is running cats. It has had the above parts for about 30k miles. This problem arose about 5k miles ago. The car has 125 on the clock. At 100k we put in a new gm fuel pump, filter,plugs and wires and o2's more for pm than anything else. The ct reads about 165-180. The tech 2 shows crank and cam reference signal while cranking. The black smoke leads me to believe no spark but damm on 8 cylinders. Or could it possibly be flooding down. The tps also show 0 throttle angle during crank. After it starts other than the smoke it runs fine and does not miss a lick. Any other ideas or help would be appreciated. There are also no vats codes stored either.
try pressing the gas pedal to the ground when it does this and see if it clears up and starts right away.. maybe a sticking fuel injector, and by pressing in the petal 80% or more will turn on the clear flood mode in the pcm and cut off fuel for a bit.
Thread Starter
Joined: Oct 2004
Posts: 5,121
Likes: 74
From: somewhere in TX
I tried clear flood a little earlier and no dice. I caught it once with the fuel pressure gauge on it and I had 55lbs of pressure. Which in turn would rule out a sticking injector. Anyone have more ideas? thanks for the help
Teching In
Joined: Aug 2004
Posts: 37
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usualy when a fuel injected car starts up pig rich its due to leaking injectors and is easly diagnosed and fixed. or install new plugs and make sure to use best fuel possible. ls1 cars are sensitive to quality of fuel and have learnedfuel tables and even have the ability to save from bad fuel by,shutdown until fuel supply level is raised in tank to simulate to p.c.m. fresh fuel supply on board. smell the oil for rich fuel smell.good luck.
you could monitor the fuel pressure as you turn off the car, and see how long it takes for the pressure to go down, to see how bad the injectors are leaking.. the fuel petal thing killed one theory.. so tuning or injecotor.
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Thread Starter
Joined: Oct 2004
Posts: 5,121
Likes: 74
From: somewhere in TX
I'll double check it later on today. But last time I had the pressure gage on the vehicle it did not bleed down over a several hour period. It was at that time I thought we may have had a pressure issue. The compression is great on all 8 cylinders too.
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Verdad Gallardo Thread Starter
Joined: Oct 2004
Posts: 5,121
Likes: 74
From: somewhere in TX
The tps showed 0% throttle angle at koeo. IT showed 0%throttle and a touch over a 1 volt koer. Is there a possiblity that the pcm could have internal problems when heated and richen the crap out of it. Everything we have discussed here has been done twice by me and another tech at our shop and both of us keep drawing a blank. I have even tried reflashing the pcm with updated programming to no avail. 
to any and all who have tried anyone have more ideas other than a rag and a match in the fuel tank. I have had a lot of the ls based engines through our shop in the last five to six years and I have never run into this before. I have had problems with the pressure regulator rupturing on the trucks but that is about it.
to any and all who have tried anyone have more ideas other than a rag and a match in the fuel tank. I have had a lot of the ls based engines through our shop in the last five to six years and I have never run into this before. I have had problems with the pressure regulator rupturing on the trucks but that is about it. Thread Starter
Joined: Oct 2004
Posts: 5,121
Likes: 74
From: somewhere in TX
I hope I never have a customers come in doing this. If it was not for all of the spare parts I have around this bitch would already have been out of this world in changed parts.
Thread Starter
Joined: Oct 2004
Posts: 5,121
Likes: 74
From: somewhere in TX
I finally fixed it. Until now all we had been able to manage was a few minutes here and ther to work on it. All after it had cooled off. I got the car for the weekend and drove it for about two hours yesterday. When I got back to the shop and put the pressrue gauge on it. Lo and behold It was now losing pressure. It took about twenty minutes to fall to 0. I pulled both rails and found two injectors on each side dribbling. But they only do it when hot. I let the car sit overnight with the rails out pressured it up and it would not leak a drop. I am just going to put 8 new injectors in it tomorrow. Thanks for all of the help guys.
