Sorry for this long post, but I'm having trouble with my 1997 F-250 7.3L truck.
My problem started as a no start when hot issue. It would crank fine when cold, but when it heated up, no go.
I researched the forums, checked the oil level in the HPOP reservoir (each time it wouldn't start), checked for fuel in the fuel bowl, drained fuel bowl and watched it fill back up, checked all my fuses in the cab and under the hood, etc, etc. Found nothing abnormal, so I downloaded the Torque Pro app and monitored my engine parameters.
When the truck would start, everything looked fine. HPOP pressure would jump immediately up to 900-1200 at start and go up to 2800-ish driving. Sensor voltages and duty cycles looked good, etc.
When the truck wouldn't start, my HPOP would only hit around 350, IPR duty cycle would go up in the 70's with no CEL's, and I HAD movement on my tachometer.
Not sure what to do next, I replaced my IPR with a new Ford IPR and changed the oil. The no start when hot remained.
I was leaning towards and electrical problem because my HPOP seemed ok, both during successful start and while driving, so I started moving wire bundles, etc, trying to get a hiccup. During this, I noticed when I moved my ICP pigtail, the engine would rev up slightly.
So I changed my ICP sensor and ICP pigtail with new Ford parts. The truck fired up both hot and cold. It still cranked slightly longer than normal when hot and I now had a hard CEL (although for some reason, I have yet to get Torque Pro or my Code Reader to pull that DTC). Both say "No DTC's stored in PCM" when I've tried, but the CEL remains on. Other than that, the engine ran good and the parameters looked normal.
Scratching my head about the long start and the CEL, I began looking at my ICP pigtail wiring because I my wiring diagram wasn't very clear.
Turns out, I had VRef (DB/W) wire going to the lower ICP connector pin (ICP signal circuit), and ICP signal (DB/LG) going to the Vref pin in the connector. The truck still ran pretty good at this point. Idled great, started hot and cold, etc.
I swapped those two wires to the correct positions, thinking this was my "easy fix" and now the truck is dead in the water.
I intermittently loose Vref voltage. It's throwing several codes, ie, 472 - Exhaust Press Sensor Low Input, 198 - EOT High Input, and 1661 - Output Circuit Check Low Input (the battery's were a little low from repeated starting attempts at this point).
And another thing, which baffles me, is my HPOP pressure has fallen off to almost nothing while cranking. Maybe 100 psi (tops).
I'm kind of lost at this point and I didn't want to post all this in the forum.
I'm thinking maybe a shorted ICP, faulty IDM or PCM, faulty IDM / PCM relay, or wiring/ground issue.
I'm gonna put my old ICP sensor back in later today and see if that changes anything.
Anyway, I'm sorry for the long post. I wanted to get all the details of my problem in and would really, really appreciate any advice or direction anyone might could provide to help me figure this out.
Thank you
My problem started as a no start when hot issue. It would crank fine when cold, but when it heated up, no go.
I researched the forums, checked the oil level in the HPOP reservoir (each time it wouldn't start), checked for fuel in the fuel bowl, drained fuel bowl and watched it fill back up, checked all my fuses in the cab and under the hood, etc, etc. Found nothing abnormal, so I downloaded the Torque Pro app and monitored my engine parameters.
When the truck would start, everything looked fine. HPOP pressure would jump immediately up to 900-1200 at start and go up to 2800-ish driving. Sensor voltages and duty cycles looked good, etc.
When the truck wouldn't start, my HPOP would only hit around 350, IPR duty cycle would go up in the 70's with no CEL's, and I HAD movement on my tachometer.
Not sure what to do next, I replaced my IPR with a new Ford IPR and changed the oil. The no start when hot remained.
I was leaning towards and electrical problem because my HPOP seemed ok, both during successful start and while driving, so I started moving wire bundles, etc, trying to get a hiccup. During this, I noticed when I moved my ICP pigtail, the engine would rev up slightly.
So I changed my ICP sensor and ICP pigtail with new Ford parts. The truck fired up both hot and cold. It still cranked slightly longer than normal when hot and I now had a hard CEL (although for some reason, I have yet to get Torque Pro or my Code Reader to pull that DTC). Both say "No DTC's stored in PCM" when I've tried, but the CEL remains on. Other than that, the engine ran good and the parameters looked normal.
Scratching my head about the long start and the CEL, I began looking at my ICP pigtail wiring because I my wiring diagram wasn't very clear.
Turns out, I had VRef (DB/W) wire going to the lower ICP connector pin (ICP signal circuit), and ICP signal (DB/LG) going to the Vref pin in the connector. The truck still ran pretty good at this point. Idled great, started hot and cold, etc.
I swapped those two wires to the correct positions, thinking this was my "easy fix" and now the truck is dead in the water.
I intermittently loose Vref voltage. It's throwing several codes, ie, 472 - Exhaust Press Sensor Low Input, 198 - EOT High Input, and 1661 - Output Circuit Check Low Input (the battery's were a little low from repeated starting attempts at this point).
And another thing, which baffles me, is my HPOP pressure has fallen off to almost nothing while cranking. Maybe 100 psi (tops).
I'm kind of lost at this point and I didn't want to post all this in the forum.
I'm thinking maybe a shorted ICP, faulty IDM or PCM, faulty IDM / PCM relay, or wiring/ground issue.
I'm gonna put my old ICP sensor back in later today and see if that changes anything.
Anyway, I'm sorry for the long post. I wanted to get all the details of my problem in and would really, really appreciate any advice or direction anyone might could provide to help me figure this out.
Thank you