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Discussion Starter #1
Hey fellas,

My 95 F250XLT 7.3 ZF5 4x2 intermittently has some combination of losing power, dying, extended cranking after dying, or just plain crank-no-start

I recently acquired an MTG2500 scan tool that will data link with the truck. So far, I haven't been able to get it to die while looking at the PIDs while idling (don't want to drive it right now, because it's hot here in the Mojave and I don't want to have to walk)

Findings / steps taken so far:
1. About a year ago, my truck died at a stop light and let a bunch of oil out (my ICP sensor gave up the ghost) - had to travel that day for work and needed it when I got back, so I had a local shop replace it
2. More recently, I replaced my CMP (some call it a CPS). No change to issue
3. Fuel pump seems good - had gauge on it when truck died at idle once and it was 60 PSI right up til it died. Fuel bowl full any time I pull the cover. Cranking the truck by jumping the starter solenoid also showed good fuel pressure even though it wouldn't start
4. Most recently, the issue became more frequent, so I got a MTG2500. No DTCs stored in PCM. Passes KOEO and KOER tests
5. Some PIDs at idle from the MTG2500 (truck did not die):
ICP(V) 0.86 to 1.01
ICP(PSI) 565 to 596 (I imagine this is calculated from the ICP voltage)
IPR(%) 11 to 12

If I'm going to look at my PIDs while driving / under load (sadly it's got a ZF5 so I can't just stall the torque converter) what other PIDs should I be looking at?

And is there a good resource online for what my PIDs should be under various conditions? Like, a table of IPR percentages and ICP pressures for this vintage 7.3?

Ultimately, I just want to some peace of mind the next time I throw some parts at it, I will have hope of changing the nature of the issue with my truck. Didn't feel so bad about throwing a CMP at it since now I have a spare in the glove box, but things will start to get a little spendy if I do a the IPR and turns out I needed a HPOP, UVCH or an IDM etc.

I wouldn't think it's injector seals since the issue happens hot or cold, and sometimes when it dies I have extended no-starts, but I suppose it could be sticking injector(s)? Which is, uh, well, a lot of money too

Any guidance is much appreciated, thank you
 

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When it's difficult to start is there white smoke coming out of the exhaust?

Check the tin nut on the back of the IPR and verify there's no oil in the ICP connector. I wonder if your IDM is on it's way out.
 

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Discussion Starter #3
There's a small amount of white smoke, I'd say. Definitely not mosquito fogger status

Tin nut is there and is tight, ICP connector is dry

I noticed the two-wire connector on the turbo compressor housing is missing its retainer clip, was loose, and the inside was covered in oil. I'm guessing that's IAT? Not sure that would explain these symptoms though

Looks to me like the Y pipe, plenums, fuel bowl all would have to come out to do the IPR valve on this thing, if I end up going that route. So that's a lot of seals etc.

Would not be great to do all that work and realize "welp, it's my IDM, actually"

As a former dealership tech, it's frustrating to know I couldn't take my truck into a shop for this kind of issue and expect them to troubleshoot it correctly / fix it with first repair attempt / not completely bend me over while it was torn down while insisting it needs x, y, z while they're in there, and still hack it up and not change the issue anyway
 

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Discussion Starter #4
Hmm, I looked into the IDM more closely than I had before (didn't realize it was so straightforward to refurbish)

I guess I'll just have to look at my PIDs when it dies and see if my ICP actually changes when it stumbles / stalls out. If it doesn't, I can't imagine it's my IPR valve or solenoid. It wouldn't make sense that the valve is "sticking" when it dies at idle, but the solenoid going out could explain that

Another thing is that the issue doesn't seem to be related to temperature, whether the truck has been running or been sitting, etc. Which to me would suggest it's probably not the IPR solenoid going out, and would be better explained by bad contacts in IDM

Then again, I don't know enough about these trucks yet to be confident in my reasoning
 

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The easy part is fixing it, hard part is finding the issue.

Without a long explanation, the IPR is just a solenoid aka electromagnet. After many heat cycles they wear out and get real finicky. They usually show their failures when hot but can certainly do it when cold.

I'd watch the IPR % in relation to ICP pressure and see if IPR % increases and ICP stays the same. It could point to a failing HPOP but i'd expect you to have other issues for that.

Remove the IDM and shake it. Listen for water sloshing around, common cause of failure.
 

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Discussion Starter #6


Figured I'd run the scan tool while I went to go grab some groceries, and wouldn't you know it - crank no start!

That's while cranking. Looks like my IPR valve needs replaced

Gonna do some YouTube "research" but am I right that I've basically gotta pull my y pipe, plenums, and fuel bowl to replace that thing?

Seems like a good time to do the lift pump too. Is resealing the fuel bowl a can of worms or should I do that while I've got it out too?

Any brands / vendors in particular good for the IPR, fuel pump, other seals?
 

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Is your ICP at 0 while cranking??

Check your HPOP reservoir before cranking. If it's low or empty then the HPOP is the problem. But while cranking you should see more than 15% IPR.
 

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Discussion Starter #8
Sorry, I meant the waveform was while cranking

HPOP oil reservoir is full and while cranking IPR climbed from 15% to 55% but ICP plateaued at 155 psi
 

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Full HPOP and IPR demanding 55% with only 155psi is pointing to HPOP.

The demand is there from the IPR but the HPOP is not producing the pressure.
 

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Discussion Starter #10
I am under the impression that the 55% is duty cycle sent to the IPR from the PCM

IPR % climbing from 15% to 55% while ICP plateaus at 155 psi suggests to me that the IPR is remaining open and not allowing enough pressure to build to fire my injectors

Moreso since my ICP plummets to zero while I'm KOEO, before my IPR % drops
 

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Discussion Starter #12
Pulled my IPR and the o-rings at the tip were trashed

Coil ohmed out good at 11 ohms so that wasn't it, but I imagine those o-rings could have something to do with it

Gonna order an IPR, fuel bowl seals and some other misc. stuff and hope for the best

Any input on a good vendor for those things?

A vendor for a dead head kit to test HPOP directly (taking injectors out of equation) would be helpful too, in case the IPR doesn't solve my woes
 

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Pulled my IPR and the o-rings at the tip were trashed

Coil ohmed out good at 11 ohms so that wasn't it, but I imagine those o-rings could have something to do with it

Gonna order an IPR, fuel bowl seals and some other misc. stuff and hope for the best

Any input on a good vendor for those things?

A vendor for a dead head kit to test HPOP directly (taking injectors out of equation) would be helpful too, in case the IPR doesn't solve my woes
I do have all those parts in stock.
 

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Discussion Starter #15
FYI, just as a quick update, I ended up replacing my IPR and, welp, didn't change the nature of the issue

I ohm tested the yellow/red wire terminal from IPR connector back to my PCM connector (pin 83, also yellow/red), and had continuity, even while manipulating the harness at various points between PCM and IPR

I had previously verified that I had battery positive voltage at the IPR connector red wire terminal

When I did the IPR I also replaced my leaking fuel bowl and the hoses, and the reman fuel bowl came with a new harness, so I cut the old IPR pigtail off and spliced ~3 feet of wire + alligator clips, hot wired my new IPR (battery positive to the red wire, battery negative to the yellow/red wire), and wouldn't you know it: the old pig fired right up and was showing ~3700psi for my ICP (so I know my HPOP is healthy) with the new IPR closed

I pulled my PCM and when I took the cover off on my work bench a solid state relay fell out of it (lol)

My PCB troubleshooting skills are very rudimentary (read: terrible), and after looking at the board for a while I didn't see any bare relay connections with obviously broken solder joints, and I didn't have any luck in my blind ohm-testing of the relevant connector pin on my PCM back to components on the board, so rather than chase my tail I ordered a reman PCM

That should be coming in this coming week, and I'm pretty confident my truck is going to be back to killing bugs once I drop it in

I don't know much about these trucks specifically, but a PCM going out seems pretty abnormal based on my google "research". It hasn't had a chip since I've owned it, but there is a bullet hole under the dash where I imagine a switch for a chip used to live when it belonged to one of the last guys, so I guess that could explain it

Just thought I'd share since it's sort of "a weird one" that defied conventional wisdom on the HEUI system in these trucks

I'll post an update after I put the new PCM in there, but based on my troubleshooting and findings I'd be floored if this didn't fix it
 

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Thanks for the update.

Read through the forum and you'll notice very odd trends. One week there was 4 people who had bad IDM's. Even a burnt tail light has caused people to rebuild their transmission and even sel their trucks.
 
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