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Info: 94.5-95 7.3 engine in a 97 f350 truck. Truck let me down on edge of highway few weeks ago, towed it home etc. Inital issue was CPS sensor faulty and bought multiple motorcraft/ford cps with different symptoms when engine started. After playing abith with cps's, engine wouldn't start, only crank.

-Checked wiring and did ohms/voltage tests from cps to pcm 104 pinout and everything is good with wires. I also physically cheched the 3 wires onch-by-inch. Retaped everything back up.
-bought new PCM, ran for 30min idle, next morning back to problem before, no start, only crank.
-Got my AE out again and found low ICP pressure.
-Dead headed hpop both hoses, manual 3000psi gauge on one hose, plug on the other. 1st crank 3000+psi, 2nd crank couple hundred, few cranks after that 500 dropping to 0 with each crank. Opened plug to see if any oil is coming out, comes out in pulsesas a very slow flow (probably normal but no high pressure assuming)

-All the time charging batteries between cranks and 30amp-engine-start-mode when cranking.
- made a plug connector wiring tool for direct IPR to batteries for few seconds when cranking to bypass the pcm.
-Bought new alliant IPR. Engine crank, no start condition as before. No change in deadheaded hoses with gauge on.
-Hpop resevoir was always full when i cranked (i did have to start filling it at one point) im guessing LPOP only supplies oil properly to hpop resevoir when engine is actually running.

-Resevoir went empty overnight. Took resevoir off to see properly oil level and it looks like it went all the way down to where there's a hole going to HPOP (im assuming). The other round(1/2"diamater hole) I'm assuming is where oil comes from the LPOP to supply the resevoir.

-hpop reservoir empty over night leading me to think hpop has a internal leak to oil pan as i saw oil level went up on dipstick from my check the day before.

1- If the hpop has a check valve, if faulty or stuck, would it bypass the closed (energized) IPR somehow and not let it build pressure? If not then pump is assumed faulty even after going trough to IPR with edge filters as required by pump?

2-Would i assume correctly from above tests that HPOP is 100% faulty and needs replacement?

The reason i ask, is that i have a 24month warranty and could send it in but thinking when they bench test it that it passes thir test and i end up wasting time removing fuel filter housing and pump for nothing.

Trying to understand the internals of the pump more exactly and if by small chance debri could reject the warranty of a replacement new pump and my time lost removing it plus shipping it etc.

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How low was ICP? You need greater then 500 psi to fire injectors. Was HPOP reservoir filling up when you deadheaded the HPOP lines? Thinking perhaps it’s not filling as you suggest. No other AE Diagnostic codes? You’re also gonna see some trapped air entrained into system unhooking HPO lines.

In respect to CPS, some 94-95s engines had casting errors on the front engine cover, impacting the seating depth of the CPS. International had a shim kit that spaced the CPS further away from timing wheel. At that time the CPS was very sensitive to distances from timing wheel. I had an early 96 truck (so could have been above engine), whereby I turned down the seating depth (of plastic CPS collar) on a lathe so it would fit closer to the timing wheel. That was when the CPS’ers where $250 each, (FMCo fawkers...). Anyways that worked for that specific engine. That engine would miss/run rough went it got hot under full WOT pulls.

You are probably aware the 95 HPOPs have an anti drain valve so the HPOP doesn’t drain out when parked over night. Might be that malfunctioning, sorry couldn’t help more. Is you HPOP new or aftermarket?

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