1980 mack fuel issue

Discussion in 'Mack Forum' started by Cjkcustoms, Mar 8, 2022.

  1. Cjkcustoms

    Cjkcustoms Bobtail Member

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    Mar 8, 2022
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    Hi guys I have a 1980 mack I'm trying to get running correctly. It starts and runs but when it idles for about 5 min it stumbles and stalls out. When this happens It cranks long and finally starts. I thought it was sucking air so I replaced all the fuel lines as I thought it was sucking air. The fuel filters are new and have been filled I've primed all the way to the injection pump and this still happens. I'm a mechanic but not a diesel mechanic. I understand how the engines work but when It comes to drivability issues I'm laxed. I'd like to exhaust all possibilities before I shoot the lock off the wallet for an injection pump
     
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  3. rbrtwbstr

    rbrtwbstr Road Train Member

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    When it dies, did you spin the fuel filter off to see if it has fuel at the filter?
     
  4. Cjkcustoms

    Cjkcustoms Bobtail Member

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    Mar 8, 2022
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    Yes primary filter is full secondary filter is a little low
     
  5. Cjkcustoms

    Cjkcustoms Bobtail Member

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    Mar 8, 2022
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  6. 062

    062 Road Train Member

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    @Brettj3876 may have some ideas.
    It’s a long shot, but take the fuel caps off and see if that helps. Vents may be clogged.
     
    Brettj3876 and Cjkcustoms Thank this.
  7. Cjkcustoms

    Cjkcustoms Bobtail Member

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    Mar 8, 2022
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    It does it if the cap is on or off
     
  8. Cjkcustoms

    Cjkcustoms Bobtail Member

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    Mar 8, 2022
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    It does it if the cap is on or off
     
  9. Brettj3876

    Brettj3876 Road Train Member

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    I was gonna say check the pickup in the tank to make sure it's not clogged. Sounds like it might possibly be the issue. Runs for a bit then whatever is down there gets sucked back up and stalls it
     
    062 Thanks this.
  10. Cjkcustoms

    Cjkcustoms Bobtail Member

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    Mar 8, 2022
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    This gives any other ideas the pick up pump is after the primary filter and before the secondary. And it is a mechanical pump
     
  11. Brettj3876

    Brettj3876 Road Train Member

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    At least there's no electronics to worry about Lol
     
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