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No start. How does ECM get oil pressure signal?

4230 Views 26 Replies 9 Participants Last post by  bukhntr
I'm working on a no start situation and I believe I may have lost lube oil pressure. Does the ECM require an oil pressure signal to start or will the engine start with no pressure until the HPOP reservoir is empty?

Does anyone know how the ECM gets the oil pressure signal? I know the sending unit on top of the HPOP supplies the dash guage with information but does it also signal the ECM that there is adequate oil pressure to start?

The HPOP is full. Engine has plenty of oil. I have changed the CPS and IPR and have tried disconnecting the ICP, but still no start.

I have checked for codes and have none except for low ICP signal when I disconnected it and a TPS signal which I always have since I spliced the wire for my idle throttle control.

Am I missing something here? /ubbthreads/images/graemlins/shrug.gif /ubbthreads/images/graemlins/confused.gif
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have you verified that you dont have a cracked pickup tube?? air being drawn causing oil to foam.
have you verified that you dont have a cracked pickup tube?? air being drawn causing oil to foam.

[/ QUOTE ]

No I haven't. Could foaming oil cause the high pressure pump to be that erratic. I have changed injector o rings and got huge amounts of air in the system but never has it ran so poorly or outright quit the way it's doing.
the foaming of oil can cause the ipr valve to not function as its designed causing poor or no running. oil quality and quantity is very important to these engines.
Just finally got mine started. It was a faulty PCM. Picked up a used one to try and it fired up almost right away. The pcm controls the oil pressure of the hpop through the IPR. I could not get more than 120 psi with the old pcm. I was set to buy a new oil pump but decided to try a pcm first( alot cheaper). When it stalls open the site plug on the hpop resevoir and you can see how much oil there is in there. You may want to use a long screwdriver as a dipstick. There is no pickup tube just a hole in the bottom of the resevoir that goes straight to the pump.

Bountyhunter, Thanks for the info. Where did you buy your PCM?

Keep us posted on what you find wrong, why your truck won't start for I now have the same problem, my tach is just barely moving when cranking, I have ordered a new CPS hope that is the problem, if not I have been wanting to get an extra one to put in the glove box anyway for emergencies.

Thanks, Bill Miller.
Well finally got her back up and running right. All it took was a new PCM.

Thanks to everyone who responded and a special thanks goes to Bountyhunter. I was ready to spring for a new HPOP. My son who is a CAT mechanic also thought it was the HPOP mostly because when it wouldn't start it would not build over 150 to 200# pressure. Then when it would start it would run fine for awhile then all of a sudden the pressure would start jumping all over the place or would just all of a sudden drop below 500# and die.

I'm going to buy an extra PCM and carry in my tool box. I bought a reman unit at NAPA for $158.00. Ford wanted $460.00 also for a reman unit with $150.00 core charge.

Thanks again, /ubbthreads/images/graemlins/biggrin.gif /ubbthreads/images/graemlins/biggrin.gif /ubbthreads/images/graemlins/biggrin.gif
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