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1996 F-Superduty 7.3 won’t stay running

Discussion in '7.3L Powerstroke Diesels' started by Steven66, Jan 11, 2021.

  1. Steven66

    Steven66 Registered User

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    - 96 7.3 psd in F-superduty w/ zf5
    - Sat 5 years after supposedly running
    - Has new cps as the old one was bad
    - ICP checks out and doesn’t have oil in it
    - IPR works
    - injectors all buzz fine and check out, however cylinder #8 injector voltage is low
    - glowplugs work, has WTS, has rpm when cranking
    - Bluetooth OBD1 scanner says everything checks out (pressures all indicate that it should start fine), except for the #8 injector issue
    - Check engine light pops up while cranking and clears when the key is cycled, scanner can’t pick up a code on it at all
    - fuel bowl has new filter and has good fuel pressure and the heater works
    - had a heat gun blowing into the intake for over an hour

    After running glowplugs, the truck will initially start and run really rough for a second or two and then shut off. Immediately cranking it after that happens it will crank and you can hear it combusting on 1-2 cylinders every rotation but never starts like it did the first time. Very consistent in multiple starting attempts. Any ideas?
     
  2. greenskeeper

    greenskeeper Full Access Member

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    remove valve covers and look for oil coming from the injector spouts while cranking. All 8 injectors should be leaking the same amount of oil, indicating that they are firing.

    Block heater work? Try plugging the truck in for at least 3 hours prior to attempting to start.

    How have you confirmed the "glow plugs work" ? While you have the valve covers off you should remove each glow plug and test it by putting 12v to the plug. It should glow cherry red the entire length within 10 seconds.
     
  3. lotzagoodstuff

    lotzagoodstuff Supporting Member Supporting Member

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    +1 on plugging it in. I like the heat gun, but any additional heat you can will help with a hard cold start.

    The check engine light with no codes part seems interesting/strange. Are you using a handheld scanner or Forscan, AE or ?
     
  4. Steven66

    Steven66 Registered User

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    There's actually no block heater installed. I pulled the IDM out of the truck and was going to sell it to a buddy (no codes were thrown about the IDM when scanned) since his IDM is giving signs that its going bad. His truck started on it but sounded like it was only running on a few cylinders. It also did the same thing as the other truck where after cycling the key, it would start and rev up for a second and then it would fall on its face. Buddy has a new IDM that he's going to bring over so we can test and see if thats the problem.
     
  5. lotzagoodstuff

    lotzagoodstuff Supporting Member Supporting Member

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    FYI: newer 7.3 IDMs are supposedly better running and more robust.

    Good luck, hopefully you found your issue.
     
  6. greenskeeper

    greenskeeper Full Access Member

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    Are you sure? It should be near the oil filter. Maybe the cord is missing?
     

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