88 2.8 mpi wont start when warm

[mfre1111]

Any help greatly appriciated. I will start from the start. It was running fine and then started sputtering and died and would not restart. Had it towed home. Went out in the morning and it started right up. Once it was warm and I shut it off for about 5 minutes it would not start again. when it is cold it will start right up. I put in a new crank position sensor and have now put on 3 different coil packs from the wrecking yard. It has 45 pounds of fuel pressure when it is warm and it drops to 35 when cranking. so it has fuel to the rail. As I understand it the ignition control module controls the signal to the injectors. I am sort of stumped because I put 3 different ones on and they all did the same thing. I am thinking the computer. Any Ideas? thank you in advance.

[mfre1111]

I warmed it up until it wouldn't run and sprayed starting fluid in the air horn. It started up and ran until the starting fluid was gone. I also installed a new computer and it does the same thing. As I said before I have a brand new crank sensor and have installed 3 different ignition modules from the wrecking yard. It seems unlikely that all 3 would be bad and have the same symptoms. I suppose it is possible or also that the new crank sensor is not good. Any suggestions at all? Thank YOU

[Blue Bowtie]

It would be good to test the injector resistances when the engine is cold, then start and fully warm the engine and test the resistances again. A substantial drop in resistance could be forcing the ECM to cut off fuel pulses.

[tomj76]

Did you check for any stored codes? On my '90 the PCM will "flash" the codes through the SES light if you connect a jumper wire to the Diagnostic connector.

Also, I once had a problem, somewhat different than yours, that was due to an electrical connection to a sensor. At some temperatures the connection was good, but at other temperatures the connection was bad. In my case the connection was between the PCM and the temperature sensor (the one for the PCM, not the one for the gauge). When the engine was cold the connection was bad, and I could only run the engine at idle. In this condition the PCM was reading an off scale engine temperature and adjusted the mixture very, very lean. Once the engine warmed the connection made contact, and it ran fine.

[manicmechanix]

Blue bowties suggestion was good about checking the injector resistance. You could have a short or open when hot at the injectors or its circuit. It's not uncommon for this models injectors to act up.

Also are you getting fuel pressure for sure when the engine stalls? The fuel pump voltage is fed through an oil pressure switch once the engine is started. There is a 2-way connecter for the injectors to ECM. You should see flashing with a testlight +B at the ECM side and at the injector side you can check the resistance. I think your problem is in this injecors circuit.