1. Registration trouble? Please use the "Contact Us" link at the bottom right corner of the page and your issue will be resolved.
    Dismiss Notice

Fuel System Not Holding Prime - Help!

Discussion in 'Early CJ-5 and CJ-6 Tech' started by Henri Watson, Nov 3, 2018.

  1. Nov 3, 2018
    Henri Watson

    Henri Watson New Member

    Mississippi
    Joined:
    Oct 27, 2018
    Messages:
    23
    Really scratching my head trying to figure out why my fuel system isn't holding prime once I get it running. I'm working on my '66 Cj5 w/ dauntless v6 and have been trying to locate the source of this problem for quite a while.

    So far I have had the carburetor totally rebuilt with all new seals and gaskets, and I've replaced all my fuel lines. If I pour a half shot of gas into the carb I can get it going, and it'll sit there and run all day long, but when I turn it off the fuel falls right back through my glass filter between the pump and the carb and then I can't get it cranked again. There is no gas leaking out onto the ground anywhere. Any ideas? Any help here is greatly appreciated.
     
  2. Nov 3, 2018
    Twin2

    Twin2 wasn't me Sponsor

    Virginia Beach, VA
    Joined:
    Apr 28, 2011
    Messages:
    3,505
    just a guess . try it with gas cap loose or off
     
  3. Nov 3, 2018
    PeteL

    PeteL Member Sponsor

    Hills of NH
    Joined:
    Aug 3, 2003
    Messages:
    5,834

    I'm not familiar with the V6, but the check-valves in the fuel pump itself should prevent what you describe. And it should prime itself if they are working.

    Also be sure that a bad pump diaphragm has not been leaking fuel into the oil pan.

    Rebuild or replace the pump.
     
  4. Nov 3, 2018
    Steve's 70-5

    Steve's 70-5 Member

    Louisville, Ky
    Joined:
    Nov 12, 2009
    Messages:
    750
    Had that problem, gas was leaking from the fuel line, where the vinyl line attached to the metal line. Gas was spraying on the hot engine block and it evaporated and no leak showed up. I think Focker had this problem too. He did a thread on it.
     
    Focker likes this.
  5. Nov 3, 2018
    garage gnome

    garage gnome Rust polisher Sponsor

    Western MA
    Joined:
    Jun 19, 2009
    Messages:
    1,785
    Cheap fuel pumps will not hold a prime. Had this problem with my chevy. I put a good one on it and no more problem.
     
  6. Nov 3, 2018
    heavychevy

    heavychevy Sponsor Sponsor

    Danielsville georgia
    Joined:
    Sep 7, 2008
    Messages:
    222
    I run an electric pump in line with the mechanical. Electric pump has a switch to cut off once cranked and prime picks up
     
    melvinm likes this.
  7. Nov 3, 2018
    71CJ54WD

    71CJ54WD Member

    DC
    Joined:
    May 3, 2018
    Messages:
    152
    Makes me think your fuel pump diaphragm is weak but not torn since you dont mentions gas in the oil.
     
    FinoCJ likes this.
  8. Nov 3, 2018
    Keys5a

    Keys5a Sponsor Sponsor

    Joined:
    Jan 23, 2014
    Messages:
    1,653
    X2 on the pair of check valves in the fuel pump. It could be as simple as a piece of crud caught in the seat.
    -Donny
     
    scoutpilot likes this.
  9. Nov 4, 2018
    Walt Couch

    Walt Couch sidehill Cordele, Ga. Sponsor

    cordele, Ga.
    Joined:
    Mar 29, 2007
    Messages:
    5,264
    Think you have more than one problem. Fuel draining back out of fuel line is due to defective fuel pump. No fuel in carb is something else. The carb inlet is at the top of the bowl and cannot siphon fuel out of the bowl.
     
    70cj5134f likes this.
  10. Nov 4, 2018
    Glenn

    Glenn Kinda grumpy old man Staff Member Sponsor

    Apopka, Fl
    Joined:
    Sep 21, 2002
    Messages:
    8,199
    This is a fact that is easy to forget about. :D
     
  11. Nov 4, 2018
    Henri Watson

    Henri Watson New Member

    Mississippi
    Joined:
    Oct 27, 2018
    Messages:
    23
    I haven't checked the oil but will today. That sounds serious, would it just take a simple oil change to get it out? What kind of damage could that create?
     
  12. Nov 4, 2018
    70cj5134f

    70cj5134f Member

    East Tn
    Joined:
    Aug 18, 2018
    Messages:
    359
    1-carb should hold enough fuel to start back up ,at least 2-3 days after shutoff.
    2- I had the no fuel in line problem once, small cracks in fuel line that would
    let air suck in, but would not let any fuel leak out, because it was a suction line,
    no pressure to push out fuel.
    3- agree with others,about bad pumps,some don't hold a prime?
     
  13. Nov 4, 2018
    PeteL

    PeteL Member Sponsor

    Hills of NH
    Joined:
    Aug 3, 2003
    Messages:
    5,834
    Eventually? Low oil pressure and a wrecked engine.
     
  14. Nov 4, 2018
    Henri Watson

    Henri Watson New Member

    Mississippi
    Joined:
    Oct 27, 2018
    Messages:
    23
    Last edited: Nov 4, 2018
  15. Nov 4, 2018
    homersdog

    homersdog Tulsa, Ok Sponsor

    Tulsa, OK
    Joined:
    Jan 8, 2012
    Messages:
    1,405
    Rockauto has 3 different brands in 20-25 range. Unless Kaiser-Willys has some secret American made source, they just reselling the same stuff.
     
  16. Nov 4, 2018
    sterlclan

    sterlclan Member Sponsor

    exploring the...
    Joined:
    Feb 21, 2009
    Messages:
    2,574
    this
     
  17. Nov 4, 2018
    71CJ54WD

    71CJ54WD Member

    DC
    Joined:
    May 3, 2018
    Messages:
    152
    Now that you have a pump coming you can just drain the oil and replace the filter. Should be fine to just do that no need to drain again if you leave the filler cap off and the drain plug off while you wait on the fuel pump shipment - should all evaporate pretty quickly leaving those openings.
     
  18. Nov 5, 2018
    chrisg

    chrisg New Member Sponsor

    94555
    Joined:
    Jun 20, 2018
    Messages:
    36
    Don't wanna hijack this post but I'm having a similar situation. Mine also has a electronic pump as well as the one on the block. Don't start for a few days and the jeep doesn't want to start .... replaced all the fuel filters.
     
  19. Nov 5, 2018
    Walt Couch

    Walt Couch sidehill Cordele, Ga. Sponsor

    cordele, Ga.
    Joined:
    Mar 29, 2007
    Messages:
    5,264
    Chrisg it would be better for you to start your own post. It sometimes gets confusing when repair suggestions are acted on by the wrong poster.
     
    chrisg likes this.
  20. Nov 5, 2018
    chrisg

    chrisg New Member Sponsor

    94555
    Joined:
    Jun 20, 2018
    Messages:
    36
    Thanks walt... just reading this and will do..

    Chris
     

Share This Page

New Posts