craiso

This is a RHD postal Jeep. I have had zero problems with it until my son turned 16 a few days ago. He took it out for his first taste of freedom, and it let him know exactly what driving a Jeep is all about. Driving down the road and it just shut off without warning or CEL. No codes to speak of. The problem is crank - no start. After a long period of time it will start and run great for about 5 minutes then shut down. After it shuts down, no spark (verified with spark checker), and no fuel pressure Verified with gauge on rail). I swapped out the crankshaft position sensor, no joy. Verified with a multimeter that the crankshaft and camshaft position sensors are functioning normally while cranking. Oddly, it will try to start in neutral. It stumbles a few times, then shuts down. This does not happen in park. In drive, reverse, or 1-2 it will not crank. Can anyone explain this? It has a different NSS installed than what Rock Auto or any of the other stores say it is supposed to be. I will add photos shortly. All the grounds that I can find have been refreshed. ASD relay has been swapped out.

craiso

NSS Plug

NSS

This NSS does not appear to be the same as what can be found at Rock Auto or the other stores. Does anyone know the part number?

cruiser54

Do you get fuel pressure on initialization?

Just key on before cranking?

craiso

Thanks for the look cruiser.
No fuel pressure with the key to ON. After looking over the wiring diagrams, I am starting to think I have a ground problem. When the Jeep was running, the OBDII would connect to the code reader; after it went to no-start, the OBDII would not connect. The ground G105 is for the PCM to operate the OBDII. It also is the PCM ground for the crankshaft and camshaft sensors. I did not have a good ground on the wiring for the two sensors while cranking over the engine, but I did have nearly 5V on both signal and reference. I found it strange that both the signal wire and reference wire read exactly the same as the engine cranked. On my XJ, the signal was a pulse and the reference was 5V steady as soon as you turned the key to ON. Plan of the day for tomorrow is to find G105; I have the FSM ground diagram...wish me luck. I'll keep you posted. Still not sure about it trying to start in neutral...

craiso

Problem solved. The PCM was bad. I slaved in a PCM from a 1998 XJ and it runs like a champ. It does have a CEL because of the different transmission. Verified the no-start on the other vehicle.

cruiser54

Nice work.

craiso

Thank you sir. I was sure it was a bad ground or splice, but pulling on wires and moving the harnesses was getting me nowhere. Desperation makes you do crazy things like swap PCM. This time it paid off.