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97 non California truck all stock, 168k. Was running bad, then quit running all together. Buddy hooked up his magic tablet and found 125 psi oil while cranking, unplugging ICP had no effect. Replaced IPR, truck fired right up and ran very well. Shut it off and immediately had to crank excessively to start. Eventually it started then died at idle and would not re-start. Now hi pressure oil is at 55 psi while cranking. Cleaned new IPR, re installed, and won't start. Unplugged ICP and it ran well. Drove it 20 miles or so, shut it off, and 2 hours later it wouldnt start again-clearly not making any high oil pressure again. Pulled IP R and cleaned it and still won't start.

Engine oil is cleAn and full, have lube oil pressure while cranking
HPOP is full to top
New Motorcraft CPS, have tach signal while cranking
New fuel bowl wiring harness
New EOT sensor and pigtail
New ICP pigtail
UVCH look like New externally


Hoping to get some ideas on this as I really want to avoid taking it to a shop if I can. I'm a competent mechanic, but have little experience diagnosing an engine like this
 

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What I would first do is double check that the electric plug that goes onto the IPR is clean and in good shape. There is an o ring in that plug so make sure it has not fallen inside the connection. Also check the harness wires that go into the IPR plug, over time I’ve had the insulation degrade and short at that location. Also ensure the tin nut is snug on the rear of the IPR.

At issue it appears you have low High Pressure oil, this can be caused by the electrical system (I.e., IPR signal) and/or a leak some where in the HPO system, like an injector, failing HPOP.

As you may know you need 500 psi high pressure oil to injectors to fire the truck up. You’ve entrained air into the high pressure system through changing out the IPR and it’ll take a little while for it to work out of the system. Not surprising it may have taken an extended crank to fire up, especially if you didn’t top up the HPOP reservoir after IPR change/cleanings. Was there debris on the IPR?

Is the fuel filter media black, like saturated with diluted engine oil, this can be an indication that injector o-ring(s) have failed leaking HP oil.

If it were me I’d double check the electrical system as noted above, because 168k seems somewhat low mileage for HPOP or injectors (o rings) to be going out. Next I would probably purchase a few high pressure oil fittings, couple rail plugs, 3 ft of high pressure hose and a quality liquid gauge that reads to 4000 psi. You can then isolate the high pressure oil pump, each high pressure oil rail to determine if you have a leak in the system. Do a search on here for greater details.
Let us know how you make out with the electrical connections.
j
 

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Discussion Starter #3
What I would first do is double check that the electric plug that goes onto the IPR is clean and in good shape. There is an o ring in that plug so make sure it has not fallen inside the connection. Also check the harness wires that go into the IPR plug, over time I’ve had the insulation degrade and short at that location. Also ensure the tin nut is snug on the rear of the IPR.

At issue it appears you have low High Pressure oil, this can be caused by the electrical system (I.e., IPR signal) and/or a leak some where in the HPO system, like an injector, failing HPOP.

As you may know you need 500 psi high pressure oil to injectors to fire the truck up. You’ve entrained air into the high pressure system through changing out the IPR and it’ll take a little while for it to work out of the system. Not surprising it may have taken an extended crank to fire up, especially if you didn’t top up the HPOP reservoir after IPR change/cleanings. Was there debris on the IPR?

Is the fuel filter media black, like saturated with diluted engine oil, this can be an indication that injector o-ring(s) have failed leaking HP oil.

If it were me I’d double check the electrical system as noted above, because 168k seems somewhat low mileage for HPOP or injectors (o rings) to be going out. Next I would probably purchase a few high pressure oil fittings, couple rail plugs, 3 ft of high pressure hose and a quality liquid gauge that reads to 4000 psi. You can then isolate the high pressure oil pump, each high pressure oil rail to determine if you have a leak in the system. Do a search on here for greater details.
Let us know how you make out with the electrical connections.
j
IPR wiring is new to the plug at the fuel bowl and in good shape. I cleaned the plug for good measure. Tin nut is tight.

Fuel filter shows no signs of oil in the system.

Filled HPOP with oil after reinstalling IPR, confirmed it's still full after cranking.

No noticeable signs of debris in IPR when I cleaned it either time. The slug took some coaxing to get out, but probably just sticking from the oil. Rattles free after reassembling.

I think ill unplug the harness at the fuel bowl and look for issues then crank some more to see if I can build some hi pressure oil. I've probably already cranked a minute total over several cycles. If that doesn't work, it looks like ill need to buy a rig to pressure test the hi pressure oil system like you mentioned.
 

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I may have interpreted your post incorrectly, but if you disconnect the harness at the fuel bowl (IPR wiring is part of that), you won't build pressure. The IPR when unplugged will dump the oil back to the oil pan. Cheers!
 

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Hey Pumpkinr reread your original post, sorry missed (and forgot too) the new fuel canister harness includes the IPR plug. Question, after driving for 20 min with ICP unplugged, you parked it for 2 hours then would not fire up. Even (presumably) you unplugged the ICP again, or left unplugged? And no diagnostic trouble codes came up when scanned?

When you look inside the ICP connection plug you shouldn’t see any oil or oil residue, sometimes the ICP sensor will leak and go faulty. By unplugging (ICP) the Power Control Module reverts to stored oil pressure tables and by passes “live” pressure inputs by the ICP I think. Again with the relatively low mileage on your rig I’m tending (and could be way wrong) that this (low oil pressure no start), is an electric signal fault, short, poor connection and not a materials e.g., injector O ring, HPOP failure.
j
 
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