1995 7.3 Shuts Off After Warm Up

Discussion in '94-97 PowerStroke Engine, Drivetrain & Chassis' started by lotzagoodstuff, Mar 12, 2018.

  1. lotzagoodstuff

    lotzagoodstuff SDD Junior Member

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    Dec 4, 2013
    Vancouver, Wa
    I posed this over on Oilburners as I'm a former IDI guy, but I know there's more traffic over here and definitely more expertise.

    I'll try to summarize what I've done so far in hopes somebody thinks of something I haven't thought of yet.

    My truck is a 1995 Powerstroke, totally stock except for a TW Performance 6 position chip (I installed this to make the shift points nicer and I've never had it on anything but "stock" or "+40HP" position) and the big open air filter modification. The truck has a tick over 100K on it, and other than the trans being a little soft for the last 10K miles I've owned it, it's a pretty decent dually.

    Over the last six months, it smoked heavily during cold starts, cleared up and ran fine when warm. It got worse and worse starting as the winter temps got colder, so around Christmas I decided that I'd swap to thinner oil to make it easier on my starter, and it smoked more on startup but seemed to run about the same. I stopped driving it as I try to keep the salt off of it over the winter months as much as possible, and I figured I'd put a set of injector orings in it to see if this helped the smokey cold starts. I used Alliant parts as it seemed like these were the best replacements. The old ones were a little hardened, I changed them all out, but didn't help much, and I parked it for about a month as it got cold and I got busy with the holidays. The next time I started it, I let it get warmed up and when I shut it off, it would start and run for about a second, and then shut off, like you turned the key off. If would do this as many times as you restarted it.

    I figured maybe it was a bad IPR that was bleeding off too much pressure to fire the injectors when warm, so I rebuilt the IPR. It didn't look terrible (it was interesting that it didn't have a split backup ring on it, but it does now, again I used Alliant repair kit parts) but it didn't change anything and the warm engine shut off continued.

    I have unplugged and inspected the ICP, no oil in it, and when I unplugged it running, this was the only time I've ever gotten the check engine light to go on.

    Then I figured I'd bite the bullet and buy a blue tooth adapter and take a look at the electronic data via Forscan. Nothing appears out of range, it never throws any codes, but the problem persists.

    Last week I was convinced that maybe I had a bad TS Performance Chip, so I uninstalled it. No change, still shuts off when warmed up, no codes, etc.

    If I had to guess, I'd say that maybe I have a bad ECU, but I'm getting tired of throwing parts at it so I figured I'd get some additional eyes and thoughts as I'm pretty used up and in reality there's way more diesel experience and insight on this forum than I have in my mushy brain.

    All I know is that the engine starts cold, seems to run ok in the cold start "mechanical" start up mode, but something is killing it when it gets up to temperature. Something that doesn't give me any codes.

    I am attaching a Forscan recording, and here's another couple of things that I've already done:

    1. I tested all the glow plugs and the relay when I had the injectors out. I inspected and tested the harness side of the glow plugs too. It starts cold just fine, which is kind of funny: it's runs better cold without any computer controls
    2. I've had it running for hours at a time, there's no air in any of the HPOP or fuel side of the injection circuits as it has been run sufficiently to clear that.
    3. I have buzz tested the injectors and they all passed.
    4. I have run the KOEO tests and also got no issues found.
    5. I have the OBD blue tooth adapter so I can run all the diagnostics available with Forscan, but I've never seen any codes or Check Engine light (with the exception of the unplugged ICP)
    6. I totally agree with the IPR, ICP or CPS being a potential culprit. I kind of wish I'd have bought a brand new IPR, but I figured I'd rebuild it first. I also have a brand new CPS that I haven't installed yet as I have always heard that if the tach wiggles when you are cranking it, the CPS is good. I'm trying not to change too many things at once.
    7. I have recorded it running, but I'm not that sure of what I am looking for as I've never used Forscan before, but from what I can tell the sensors are measuring with throttle variation, which seems "normal", but again I don't really have any experience for a baseline. If anybody has any input for what I should be monitoring/recording with Forscan, I will be happy to try and post.

    I'm all ears at this point and I've got plenty of humble pie to serve myself for not figuring this out on my own, but I'll take any help I can get.

    Thanks in advance for any help or insight

    Attached Files:

  2. Mick

    Mick 97 Powerstroke

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    Nov 1, 2006
    I haven't experienced this problem with my truck but I have with my snowmobile. It would shut off and not start backup when it got up to temperature. When cold, I started the machine and I took a hairdryer and heated each component and eventually hit one that made the engine shut off. Unfortunately it was the engine control module that cost more than I paid for the snowmobile to replace.

    I'd try the same with your truck. With the engine cold and running I'd heat the IDM and other components visible including the ECU.

    Might also be something wrong in the wiring which is difficult to check.

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