As some of you know, I've been trying to diagnose a misfire that turned into a sudden shutdown after a WOT run on a test drive. The ICP seems to have tanked all at once, and won't come up enough to even allow the IDM to fire the injectors. When the oil was hot on Saturday, it wouldn't even come up past 25 psi. While cold (31F EOT) today, the highest reading was 260 psi. Before this happened, the ICP would come up to about 2800 while cranking. I may be wrong, but 2800 seems a little on the low side when cranking?

As of this morning, the truck had sat for about 48 hours. The first thing I did today was to check the HPO reservoir, which was full. Oil level in the pan is also full. I pulled the valve cover on the driver side since that was the side I suspected to have a problem. While cranking, I saw no injector top o-ring oil leaks, and all injector o-rings were replaced within the last 50 miles. I also logged some data with Torque Pro while cranking:



The maximum readings in the graph are
ICP - 260
IPR - 64.17
PW - 53 microseconds
RPM - 131


Right now, I'm thinking it's one of these issues, in no particular order:

• Failed injector o-ring
• Physical injector failure
• Stuck/failed IPR
• Cratered HPO pump

For some reason, my gut is telling me the HPO pump took a dive, but I'm not going to just throw parts at it until I can test everything. If anyone can think of something else I may be overlooking and can easily check, feel free to let me know!

ALSO, I went to a local hydraulics shop to get fittings to cap one HPO hose and adapt the ICP sensor to the other HPO hose, but they didn't have anything that would work. Does anyone have the size or part numbers for the quick release fittings and thread sizes? I'd like to isolate the heads and check their pressures and the HPO output itself before I get too much deeper into this.

 

I doubt it is the HPO pump itself. A stuck/failed IPR is the most likely candidate, and can give you misfire type of sensation while driving when it is going out. I went through the same thing on my wife's Excursion when it was at about 150K miles. It would act like a bad misfire while it was cold, and then run fairly normal when up to temperature. As the IPR demise progressed, it would occasionally just cut off as if it were a CPS. Hooking up AE and seeing the low HPOP pressure on startup, though, told me it was the IPR, and upon replacing the IPR, the truck ran like gold again.

Also, check the tin nut on the back of the IPR solenoid body to make sure that it is tight. If that nut gets loose, it can create failed IPR symptoms as well.

 

The reason I was leaning toward the pump is that I'm jinxed, and I know it, lol. I swapped the IPR solenoid from my old engine to this one and I was sure I tightened the nut, but I'll definitely double check it. If that doesn't show any improvement, I'll keep on diagnosing it bit by bit, I suppose. Thanks for the suggestion; that would be an easy fix if it turns out to be the problem.

 

With the miles you have on your vehicle, I would try it out. I have a brand new IPR, but it is slated to go into my HPOP very shortly. Otherwise, I would offer to let you try it out.

Perhaps someone else has a spare IPR they might could loan to you for a diagnostic effort.

 

The IPR has 87k on it, but the engine did sit for a year without being started. I have the one from my old engine with 217k if I need to swap it in to test it, but thanks for the offer.

 

IPRs can be repaired... as well as cleaned. I had one that was stuck and cleaning it got me running.

You should really get about 2200 PSI ICP at cranking, 2800 PSI is way too high (if it was a sustained reading on a stock tune... but spikes are OK). What was your IPR when it did that? 31% is about normal for 2200 PSI ICP. If the IPR was significantly lower than that, the PCM was trying to tell the IPR to back off, but the IPR copped some kind of attitude.

 

I may be wrong about the 2800 psi, it may have been 2200. I didn't log any data last week, and might be mis-remembering it. I don't remember seeing anything out of whack with the IPR DC numbers at that time.

 

i would not rule out the hpop being dead. i had one that ran great (185K) shut the engine down came back in a hour and it would not start. towed it back new ipr no help new hpop and i started right up. sent it to Jody and he pulled it apart the the emergency blow off had blown? what made it happen your guess is as good as mine, as the oil was hot and it was 90* out side so no cold oil and the oil had less then 1000 miles on it.

could you see oil coming out of the injectors at all?

 

I haven't ruled anything out at all yet. There was no oil from the injector spouts, but there also wasn't enough HPO pressure for the PCM to signal the IDM to fire the injectors. Tomorrow is supposed to be a nice day, so I'll be back at it in the morning to do some more diagnostics.

 

Whuuuh? Is that a one-shot deal? I guess I know what I'm going to be reading up on now.

 

that is was he told me.


Hey Matt your emergency blow off valve was the problem.

Thank you,
Joey@TE

 

When that happened, did you happen to test the pressure? If you did, do you remember what it was, whether it came up at all, or was just pretty much zero?

 

When I would lose an injector o-ring, that is exactly what my ICP would do. If it got really cold and I cranked it for 20-30 secs, I could occasionally get it to start, and it would run fine...until I shut it off with warm oil, then nada. Pull the lines from the HPOP and run 125-150 psi air in and see if you hear any gurgling. I threw a T500 at mine thinking it was the HPOP and it was the o-rings. Not that I mind having a T500 now, but with my single shots, it really wasn't necessary.

 

i did not check the psi, at the time i did not have a good gauge to check it.

 

It's certainly possible an o-ring got damaged and let go when the pressure spiked. It's a little confusing that the HPO reservoir didn't drain down in 48 hrs., though. I'm going to isolate and check the pump output pressure tomorrow. If it's low, I'll swap the IPR and retest. If the pump output is good, I'll test each head individually to see if I can get this nailed down to a "most likely" cause.