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Another No Start Problem

5K views 12 replies 5 participants last post by  1997_F250 
#1 ·
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
 
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#2 ·
I would recheck your ICP connector wiring again. See the attached GIF (the wire colors and position on my 97's ICP correspond to the diagram as far as placement in the connector, except that pin C wire color is the "Econoline" LB/R in the diagram! The 1997 EVTM also has it as LB/R, so go with that. The diagram shows the connector as if you are looking into the unplugged connector face and not down on the connector when it is plugged in). If you are still having VREF issues, you may need to check for the 5V reference signal at the other sensors that use it. The MAP, BARO, TPS, EBP, ICP, and CPS all use it.

As far as the no start when hot, it can be something like bad IPR O-rings (probably not these since you just replaced IPR), or injector O-rings. Cold, thick oil will not leak past a bad o-ring as easily as hot, thin oil and let the system build enough pressure to start. A bad middle o-ring will let oil into the fuel (increased oil consumption) and a bad top o-ring will leak oil out around the at the base of the injector where it goes into the head. Cheers!
 

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#3 ·
I would recheck your ICP connector wiring again. See the attached GIF (the wire colors and position on my 97's ICP correspond to the diagram as far as placement in the connector, except that pin C wire color is the "Econoline" LB/R in the diagram! The 1997 EVTM also has it as LB/R, so go with that. The diagram shows the connector as if you are looking into the unplugged connector face and not down on the connector when it is plugged in). If you are still having VREF issues, you may need to check for the 5V reference signal at the other sensors that use it. The MAP, BARO, TPS, EBP, ICP, and CPS all use it.
Thanks for the GIF Patrick!

I know I have VRef wired to pin B as per your diagram. It's possible I may have A and C switched. The truck is at my son's house, so it will be this afternoon before I get over there to verify.
I did find the old pigtail last night and tried to match the wiring as best I could. The signal and signal return are really faded though.

Could an ICP mis-wire or a faulty ICP sensor issue cause my HPOP pressure indication to read low on Torque Pro?
I'm not sure which sensor it gets that information from. Last night was the first time I'd seen HPOP read that low while cranking since this started. Before touching the ICP, my HPOP would bounce between 250-450 psi when it didn't start.
Last night after rewiring that ICP pigtail, live HPOP during cranking would barely reached 100 psi.
 
#4 ·
My '95 has just begun to experience a similar problem - Hot, no start (or very long crank to start). Had it to the Ford shop because they were running a $50 diagnostic special before Xmas, but it would not refuse to start - though it did require a longer than normal crank.

They didn't charge me anything and said he suspected a high pressure oil problem.
He claimed to have successfully used an OBDII scanner, but did not have any results for me. I have my doubts about that (no paperwork, no charge?).

I had it to another shop a couple years ago with what turned out to be burnt connectors on the UVC gasket. They had also assured me that they would be able to read the codes. Well, I watched while the engine was barely running, CEL on, and he had no codes.

I would gladly buy the Torque Pro app and adapter if I was relatively sure it would work with my truck, which is from Canada btw.

In the meantime, I think I'll rig up a mechanical gauge kit to try to figure out my current problem.
 
#5 ·
^^^^^ If I had a '95 and didn't know the flash status of it, and had a $50 diagnostic offer at the dealer, I would ask to apply the $50 to flashing the truck, so I could use my own device of my own choosing in the future. Maybe since they didn't discover anything last time, they'll still honor that $50 offer.
 
#6 ·
If you have to, you can check the wiring by going from the 42-pin harness connector to the ICP connector (C-138). The applicable connector pins are 19, 21, & 22 and the connection is just inboard of and below the underhood fusebox. It is almost directly below the brake master cylinder. I've attached the GIF of the connector pinout for reference. Cheers!
 

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#8 · (Edited)
Two questions:

(1) Can your HPOP and/or an injector o-ring fail instantly?
Mine went from "No start when hot" to zero HPOP indication at ICP sensor.

(2) Could a faulty PCM or IDM give you a zero indication of HPOP (WTS light works correctly)?

I just hate to spend the money on an HPOP without knowing for sure that's my problem.
(I've bought a new IPR, new ICP, ICP pigtail and fuel bowl wiring harness and I still have a no start).

Advice / opinions greatly appreciated!

Thanks
 
#9 ·
The HPOP or Injector O-rings can fail instantly. At 175k, my 94 used no oil in between 5000 mile changes. Right after an oil change it used 8 quarts in 150 miles (middle set of O-rings failed and put the oil into the fuel system). I would think that you should be able to get an HP Oil pressure reading from the ICP or you would see some code related to it. I would get a 0-5000 psi gauge and plumb it into the HPOP lines with the pump deadheaded to see what the pump is doing. Cheers!
 
#10 · (Edited)
I have an update. Spent a few hours troubleshooting again today. I rechecked my HPOP reservoir when I got home and it was still full. Installed the new CPS I keep in the glove compartment to rule that out.
Next I re-verified Vref on the applicable sensor circuits and checked for 12 volts at my IPR input.
Everything checked out good.

I hooked up Torque Pro and went to live data and tried to crank (I charged the batteries last night also). The HPOP rose to a max pressure of 405.3 psi and ICP voltage was around 0.2 volts.

One thing I noticed tonight that I missed yesterday is my IPR duty cycle did not move at all. It was 14.8% when I switched on my ignition and it stayed at 14.8% during about a dozen attempted starts. I even teed the IPR control wire (pin 83) to ground to trick the IPR into giving me full duty cycle and I had no movement indication on Torque Pro.
This IPR is a new Motorcraft and was replaced about two weeks ago.
When these no start issues showed up a few weeks ago, I was seeing 60% - 70% duty cycle during no starts.
Now it isn't moving off 14.8% at any time during cranking.

I'm thinking this thing is stuck or has failed, but I wanted another opinion. Is there any way to bench check the IPR?
Is it likely this part would fail so quickly or can debris, etc, get into them and make them stick?

Thanks!
 
#11 ·
Have you pulled the valve covers off and looked to see if oil is leaking past the injector o-rings? Have you checked the engine oil level to ensure it is full? While it sounds like an IPR/ICP issue, your original post makes it sound like an injector o-ring issue. If the injector o-rings are bad you can see oil in the fuel and/or oil will leak past the injector o-rings. You also mentioned that almost no oil came out when you changed the ICP. Perhaps you have air in the system and it needs to works it way out. When I did the injectors in my old truck I had to crank it over for a dozen or so times for 15-20 seconds before it would start.
 
#12 ·
The engine oil is full but I have not pulled the valve covers yet. I'll probably do that today or tomorrow.
Last night after cranking, I did get oil out of my ICP port.

I've thought about it being injector o-rings and was looking at the engine last night.
How hard is it to pull those back two injectors on each side? It looks like the back ones would be tight to get out because of the engine firewall.

Still wondering why the IPR doesn't seem to be moving?
When it does start, using live data on Torque Pro, my HPOP jumps up to around 1000psi at idle and around 3000psi at WOT.
Would I still see those kind of pressures with a bad injector o-ring?
 
#13 ·
If your o-rings are bad you may not be able to build pressure. I believe you need 500 psi to fire the injectors. When the oil is cold it is thick compared to when it is warm so it could build the pressure. As the o-rings fail more, more oil can get by the o-rings and now you aren't able to build the pressure to start the truck. If you aren't losing oil, you should see the oil leak past the injector when the valve covers are off and you are cranking the truck over. When I did the injectors in my old truck, I spent a day and a half doing it. I pulled the rear injectors first so all the oil and fuel drained into the rear cylinders. Then I pull the rest with the glow plugs. Before anything went in I used a mighty vac to get the oil and fuel out. I then put the new injectors in and kept the glow plugs out. Then I turned it over to blow the oil out of the cylinders and hopefully get the air out of the hpop.
 
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