HELP ! '86 305 TPI wont start hot???

[joeyj]

I have a 1972 Chev Blazer that we did a 1996 305 TPI engine swap in, new wiring harness. It worked great for a few months, THEN, drive to gas station and it won't start. It cools down and will start just fine, gets up to temp and won't start. There are no other symptoms, runs great!

Turn the key on, the fuel pump comes on, build pressure to the rails. Turns over fine, one shot of starter fluid and it cranks right up and runs fine till it is shut off. Has to cool back down and we are ready to go till the next stop.

Can anyone tell me the sequence of what should happen in the electrical and gas sequence to help diagnose this problem? The '86 has the cold start injector. All grounds are in place and good. I just need help with the proper way to diagnose.

[GTP Dad]

Bad ignition module or crank position sensor. Both are heat sensitive and if they overheat the engine can stall. Start with the CPS if that doesn't work then try the ignition module. CPS is a lot cheaper too.

[joeyj]

Thanks for the info, but could you please explain, My understanding of the ignition module is that it would be spark related and not gas related???? As for the CPS, I thought the same.....Would either of these just control the Gas on startup???? I really appreciate your reply and just am anal and am looking to understand the sequence that things happen and not just swap parts, I have no money, but time. I am ignorant of the TPI system, if were carbed, no problem....I don't know what should happen to make the fuel go into the intake???

[maxwedge]

Again. any injector pulse when the engine won't start, diagnostics is the key to your problem here. Also double posting is not within the forum rules. Please focus on one or the other.

[GTP Dad]

The fact that it is stalling can be caused by many things. Heat is a killer of electrical components that is why I suggested the ignition module and CPS may be faulty. If you are saying that the fuel is shutting off then the problem could be a malfunctioning fuel pump that is overheating and causing it to shut down. Once it cools the pump will work fine. As Shep said the issue will require some diagnosis to determine the actual cause.

[joeyj]

Thanks to you both, As for the double thread,I'm new and thought I was posting on two different catagories because of my MOD, I will stay in this thread; Thanks.

I agree that diagnosis is the key here, just a note, it does not stall, it runs fine, it will run all day with no problem, just will not start once it is turned off, it has to cool down. The fuel pump is new, about 4 months old, not saying it couldn't be bad....However, when you turn the key Hot or Cold iot comes on and presurises the rails, I can push the valve on the rail and it will squirt gas all over me Hot or Cold. I used a test light on the injectors and I do have power to them with the ignition key on, don't really know what this means but they do have power. I also unplugged the cold start sensor, it will not start hot or cold with this disconnected. I can start it from a dead sleep in the morning, let it run for 5 min. turn it off and it will not start till it cools down, it does not have to run long for the problem to arise. Can you tell me what tells the injectors to start spraying fuel? This is probably what heats up and is not working, I have had two computers on this with the same results. Thanks in advance....