The Diesel Stop banner

No start. How does ECM get oil pressure signal?

4222 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
See less See more
1 - 13 of 27 Posts
Centerline, thanks for your response but I don't think it could be the ICP because I have read on this forum the engine will run in the limp home mode without an ICP signal.

I have been told by a Ford diesel tech that this engine will not run without oil pressure. /ubbthreads/images/graemlins/confused.gif
See less See more
All the fuses are good. All the wiring looks OK. No smoke out the tail pipe that I can see from the drivers seat. Plenty of fuel in the filter bowl. Changed the fuel filter changed the air filter.

The engine doesn't try to start at all.
Thanks for your response trucktech. The oil in the reservoir was poured in there by me. When the no start initially started the reservoir was dry and I added a quart. The reservoir however does not go down from cranking.

What should the fuel pressure and HPOP pressure be and where is the most convenient places to test.

No I didn't check the whole harness when I changed the IPR because I didn't remove the fuel filter bowl. As a matter of fact I had the start of a mouse nest in the valley under the fuel filter bowl. I had to take the bolts out of the fuel bowl and push it to one side to get the IPR in and out and all of the harness I could see looked alright on the outside. I guess in order to check it I will have to completely remove the filter and bowl. That is another possibility if I have good fuel pressure readings.

I would have to get a 75 mile tow to get a buzz test. That's what I'm trying to do without.

Are those pressures you gave me attainable just cranking with the starter?

Thanks for all the info.
Thanks, I killed one of my batteries with all the cranking so I have to take a break and go buy another one.
OK, here is the latest.

I took the fuel bowl out and examined the IPR - fuel heater wire loom and all checks out. Even did a continuity check.

Hooked up a guage to the HP Oil rail with the reservoir full and cranking with new batteries could only get 200# oil pressure. Checked the tail pipe while cranking and could not see any white smoke. Put a tire guage on the schrader valve while cranking and could not get any pressure reading on the fuel. Couldn't figure out a place to check the fuel pressure with a better guage. I need a 1/8" NPT and couldn't find one.

What do you guys think? /ubbthreads/images/graemlins/shrug.gif
See less See more
will it fire off of alternate fuel source and continue to run???

[/ QUOTE ]

I'm hesitant to try that because this truck had the lube oil pump go out at 70K miles under warranty and they replaced the oil pump. If that has happened again I would be running the engine with absolutely no oil pressure.

I had to take my grandson to a ball game tonight but tomorrow I'm going to check the oil pressure at the HPOP reservoir to see if I have lube oil pressure and then go from there.

I anyone has any other suggestions I'll try them.

I went out this morning and dumped a little fuel to make sure the bowl had filled after I had emptied it to get to the wiring. I cycled the tank switch and hooked up my guages. I started cranking and she lit. SURPRISE ! the pressures are as follows:

HPOP idle 700#
1500 - 700
2000 - 800
2500 - 1000#
3000 RPM 1300#
fast accel to WOT 1800#

The HPOP pressures might be a little off because my hose sprung a leak and I had a big mess to clean up.

LUBE PUMP idle - 30#
WOT - 60#

FUEL idle 60 - 70#

I don't know what I did to get it to start since I had the fuel bowl apart and out and the wire loom out and apart. I did clean a lot of lint off the FPR screen while I had it out. The truck is running but still dies ever once in a while while it is idling. The fuel guage looks like the pressure drops after it dies, or tries to die, and the same with the oil pressures.

Any more ideas?
See less See more
I've decided that the problem is a bad HPOP. I put another IPR valve and got it started with a guage on the HPOP rail. While she is running pressure is jumping all over the place and RPM's follow. The truck keeps trying to die but only when the pressure drops below 500#. Sometimes you can crank and crank and the HPOP will not build more than about 150# and she will not start.

I've started with starter fluid after disabling GP system and she will not stay running because the pressure will not get above 200#.

Thanks everyone for your help.
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.
Bountyhunter, Thanks for the info. Where did you buy your PCM?
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
See less See more
1 - 13 of 27 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.