Motor runs with IPR unplugged

DZL JIM

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A customer's truck I did injectors for.
A little history:
He bought the truck not running, though it might be injectors, so we went through them.
He's tried at least 3 different HPOP, and 3 different IPR's.
He's had the motor out and front cover off. Everything basically looked normal.
Now with everything back together, he can see oil spitting from the HPOP past the gear with res off and cranking, telling me the IPR is dumping properly.
Yet when he starts the truck he can unplug the IPR and it'll run with 2900 psi of oil pressure, then a short while it'll die and won't restart.

He's done about everything I can think of to try, anybody else have any ideas???

The kicker is he bought the truck with the HPOP sitting on the fneder. My guess is the previous owner probably ran into the same trouble and just got rid of the truck.

Thanks for any help.
 

DcMoore

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Have you tested the connector to see if it's shorted or grounded out, also continunity to the 42 pin connector? .. Just shootin at the hip here.
 

Hotrodtractor

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A customer's truck I did injectors for.
A little history:
He bought the truck not running, though it might be injectors, so we went through them.
He's tried at least 3 different HPOP, and 3 different IPR's.
He's had the motor out and front cover off. Everything basically looked normal.
Now with everything back together, he can see oil spitting from the HPOP past the gear with res off and cranking, telling me the IPR is dumping properly.
Yet when he starts the truck he can unplug the IPR and it'll run with 2900 psi of oil pressure, then a short while it'll die and won't restart.

He's done about everything I can think of to try, anybody else have any ideas???

The kicker is he bought the truck with the HPOP sitting on the fneder. My guess is the previous owner probably ran into the same trouble and just got rid of the truck.

Thanks for any help.

I had to think about this for a bit - ARE you sure the IPR is dumping correctly - or is the oil coming out from around the shaft seal on the pump from too much inner case pressure? When he starts the truck and leaves the IPR in what is the duty cycle and what is the ICP? Is the ICP being checked by a mechanical gauge or through the ICP sensor? You say the ICP is 2900psi with the IPR unplugged, is it any different with it plugged in? Could this be a case of the early front cover with a later HPOP or vice versa?

Just throwing stuff to see what sticks.
 

kyle43335

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Have you tested the connector to see if it's shorted or grounded out, also continunity to the 42 pin connector? .. Just shootin at the hip here.

that shouldnt matter. once the ipr is unplugged,it defaults open and dumps. you can hot wire the ipr and leave the factory connector unplugged,and the truck will run. issue has to be in the ipr some where. jim are these iprs that your guy is swapping all new? or is he trying used ones?
 

cowboy_dan

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is the oil coming out from around the shaft seal on the pump from too much inner case pressure? When he starts the truck and leaves the IPR in what is the duty cycle and what is the ICP? Is the ICP being checked by a mechanical gauge or through the ICP sensor? You say the ICP is 2900psi with the IPR unplugged, is it any different with it plugged in? Could this be a case of the early front cover with a later HPOP or vice versa?

Just throwing stuff to see what sticks.

I was about ready to ask the same questions. Especially about the shaft seal.
 

DZL JIM

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I had to think about this for a bit - ARE you sure the IPR is dumping correctly - or is the oil coming out from around the shaft seal on the pump from too much inner case pressure? When he starts the truck and leaves the IPR in what is the duty cycle and what is the ICP? Is the ICP being checked by a mechanical gauge or through the ICP sensor? You say the ICP is 2900psi with the IPR unplugged, is it any different with it plugged in? Could this be a case of the early front cover with a later HPOP or vice versa?

Just throwing stuff to see what sticks.

Agreed, and I don't know. I've been trying to work on it myself personally, just haven't had time.
He said he visually matched the dump port of the HPOP to the port in the front cover and that they lined up.
:shrug:
I've told him many times it seems the pump isn't dumping properly. He said he pulled the res off, and had a guy pump oil into the supply cavity and cranked the motor and saw oil coming out the port of the front cover behind the gear,
That's all I know.

If this seems to be the only possibility of the problem, I guess I need to see for myself....
 

DZL JIM

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How hard would it be to find a known working hpop and IPR and install them on the truck.

He did, 3 times.
HPOP from Joey twice I think, plus one off a good running truck. Joey couldn't find anythigng wrong with the pump at all.
It's Nnot the HPOP or IPR.
...Unless it's the wrong front cover.
 

firehunter

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Yet when he starts the truck he can unplug the IPR and it'll run with 2900 psi of oil pressure, then a short while it'll die and won't restart.

Purely a guess here...weak LPOP not able to keep the HPOP happy once it starts? Does oil pressure drop while it's running?

I dunno...
 

DZL JIM

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Purely a guess here...weak LPOP not able to keep the HPOP happy once it starts? Does oil pressure drop while it's running?

I dunno...

Thanks for the thought, but that doesn't make much sense with what it's doing. Besides, he said it's a new LPOP.

He said 100% sure the HPOP is dumping from the port in the front cover and not from around the seal.
He also said he rigged up a dump valve off his mech HPOP gauge and ran it to the oil fill cap, so with it running he can adjust psi lower and it still won't run properly.

Really at a loss here...

Someone suggested the oil cooler might mess up the LPOil system and might cause these issues. But I can't see how it would affect the HPOP building too much pressure.

Thanks for the help guys.
 

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