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Motor Trying To Quit While Driving... Aaahhhhhhh!

Discussion in 'Intermediate CJ-5/6/7/8' started by 1MtnJeep!, Jun 8, 2019.

  1. Jun 8, 2019
    1MtnJeep!

    1MtnJeep! New Member

    Texas
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    Mar 6, 2019
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    34
    Hey folks... need some tech guidance please.

    I have a 81 CJ5... recently bought it. Couldn't turn it down as it's in very good condition.

    I noticed when driving it acts like it's starving for gas... tries to shut down. If I pull over and rev the gas it seems to help. It is more prominent at higher speeds... 50+. It doesn't do this all the time, but it did it quite a few times this AM. :n:

    I'm thinking it's starving for gas, but also maybe a carb issue? Flat spot? It has the original Rochester 2 barrel carb. The motor is the 4 cyl Iron Duke with 4 spd manual. My future plans include upgrade to the Weber 38 DGES... plus I have an 80 CJ5 I am considering stripping down for parts. May transfer the full drive train over... 6 cyl 258. But I want to figure this prob out first. Any ideas? :study:

    s-l160015.jpg
     
  2. Jun 8, 2019
    Lee Bennett

    Lee Bennett Banned

    Joined:
    Jan 2, 2019
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    291
    Fuel filter backward, vapor lock, fuel tank vent???
     
  3. Jun 8, 2019
    1MtnJeep!

    1MtnJeep! New Member

    Texas
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    Mar 6, 2019
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    I'll check the fuel filter... fuel tank vent? Not sure about that... never thought about that...
     
  4. Jun 8, 2019
    Focker

    Focker That's a terrible idea...What time? Staff Member

    WA
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    Don't troubleshoot too many things all at the same time.

    Start with fuel delivery.
     
  5. Jun 8, 2019
    1MtnJeep!

    1MtnJeep! New Member

    Texas
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    Thanks will do. Gonna start with the fuel line running to the carb..... see what I find...
     
  6. Jun 8, 2019
    Focker

    Focker That's a terrible idea...What time? Staff Member

    WA
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    How old is the gas?
     
  7. Jun 8, 2019
    PeteL

    PeteL If it wasn't for physics, and law enforcement... 2024 Sponsor 2023 Sponsor 2022 Sponsor

    Hills of NH
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    How about under load, pulling a hill, etc.? Could just be a clogged filter.
     
  8. Jun 8, 2019
    Chilly

    Chilly Active Member

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    Recommend changing all soft fuel lines unless you KNOW theynwere done in last year or three. Junk lines + junk gas = no go.
     
    Lockman and 1MtnJeep! like this.
  9. Jun 8, 2019
    zila

    zila I throw poop

    Rock Springs,...
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    Oct 6, 2003
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    Ok, this happened to me on my 75 CJ.. Run, quit, run... Tried everything. Finally I drained the fuel tank and yanked it. I noticed as I was siphoning out the old fuel prior to removing that a big mess of junk came through the hose.. Cleaned the tank, blew out the lines, put a new in tank sock on and re-installed. Problem solved. May or might not be your problem too
     
    1MtnJeep! likes this.
  10. Jun 8, 2019
    1MtnJeep!

    1MtnJeep! New Member

    Texas
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    Mar 6, 2019
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    Hmmm.... prob have to do that. Funny thing... worked on 258 motors no prob. Also 2.5 L 4 cyl jeep motors no prob. This gm iron duke... fuel filter... uhhhh... feeling pretty dumb here. Time to start reading my manual.

    The guy i bought it from drove it on weekends with his wife. When i got it I put fuel treatment / cleaner in it and topped off the tank. About 6 gallons. Prob best i drop the tank... clean it.. clean the lines etc. The original owner had it parked for a while in his barn, so no telling what kinda crud is in there.
     
  11. Jun 8, 2019
    1MtnJeep!

    1MtnJeep! New Member

    Texas
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    It does want to do it more going up a hill... maybe she’s complaining about the heat here in Texas? :crazy:
     
  12. Jun 8, 2019
    PeteL

    PeteL If it wasn't for physics, and law enforcement... 2024 Sponsor 2023 Sponsor 2022 Sponsor

    Hills of NH
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    No, the point is that if the fuel supply is restricted, it will show up first during high-demand operation.

    Check your filter(s) before doing a bunch of other stuff, like "pulling the tank." One step at a time.
     
    Lee Bennett likes this.
  13. Jun 8, 2019
    zila

    zila I throw poop

    Rock Springs,...
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    Yep Mine was an uphill hater too.
     
  14. Jun 9, 2019
    1MtnJeep!

    1MtnJeep! New Member

    Texas
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    Wow... the fuel filter is inside the carb directly downstream of the inlet line...behind the large inlet nut. Who would’ve thought..:banghead:... after all my looking around the carb now to get a replacement tomorrow am to see if that cures the problem.
     
  15. Jun 9, 2019
    1MtnJeep!

    1MtnJeep! New Member

    Texas
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    Mar 6, 2019
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    Oh yeah as always i appreciate the help! We don’t have any good mechs i can talk to around here for pointers... they mostly want to plug in and see what the computer code is...
     
  16. Jun 10, 2019
    RATTYFLATTY

    RATTYFLATTY I think you need a little more throttle

    Central MN
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    Don't forget about the fuel pump. Bad diaphragm doesn't always leak out the weep hole.
     
  17. Jun 10, 2019
    Jw60

    Jw60 Sitting up n buckled down. 2024 Sponsor 2023 Sponsor 2022 Sponsor

    Sedalia MO.
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    A holy fuel line on the pull side of the pump can also cause a stumble under load, it will pull air when under load but the demand isn't enough at rest to see anything.
     
  18. Jun 10, 2019
    Lockman

    Lockman OK.....Now I Get It . 2024 Sponsor 2023 Sponsor 2022 Sponsor

    Silver Hill,...
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    Fuel filter & lines first. Like Chilly said, a soft fuel line ( Rubber ) could be collapsing under load ? I have also seen cheap filter elements, disintegrate in line, especially after sitting for some time . When you have the line removed , flush & change out your filter to a good quality one ( WIX ). At the same time, I would do a fuel pump test ( TSM has procedure, Highly suggest you get one ) a new fuel pump , on that engine , is a cheap and easy R&R.
    To reaffirm what the others have stated... Keep it Simple in diagnosing a problem . Start at your inline filter & work back to the tank , lastly. My bet is your problem is way before the tank.
    God Speed , Good luck , & please let us know how you make out.
    Richie----Lockman
     
  19. Jun 10, 2019
    Dphillip

    Dphillip Member

    Omaha NE
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    Years ago at the shop I worked at we had a car display the same symptoms, idle fine but would stumble and stall under load. It turned out to be a bad coil. I always thought coils either worked or they didn’t but not in this case.
     
  20. Jun 10, 2019
    Chilly

    Chilly Active Member

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    I've had that happen, too.
     
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