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mechanical vs electric fuel pump AMC V8

Discussion in 'Intermediate CJ-5/6/7/8' started by IrishCJ6, Jan 12, 2014.

  1. Jan 12, 2014
    IrishCJ6

    IrishCJ6 Member

    Wicklow Ireland
    Joined:
    Dec 6, 2010
    Messages:
    435
    The Jeep is a pain to start if left more than a day without starting, believe the fuel must be either leaking out or evaporating (carb has been rebuilt). The mechanical pumps doesn't seem to like priming itself and I can churn the engine over for a good 20sec + before I get fuel. I have been using easy start and with that it will start after a few squirts. From what I can make out the pump doesn't function great without the engine spinning at a raised speed (i.e. above cranking speed). I've been thinking that I should change to an electrical pump, this way as soon as the key is turned on the fuel is pumping/primed and should solve this issue.

    Question is what electrical pump are people using? and is this a good idea?
     
  2. Jan 13, 2014
    jeepcj

    jeepcj Member

    cincy, Ohio
    Joined:
    Aug 23, 2009
    Messages:
    601
    I use a Mr. gasket universal electric fuel pump on my sbc in my jeep. Its been on there for over a year and a half with no issues, this is my second one because I think the first pump I got was for 4-6cyl engines and it didn't last very long. Your engine requires 5-7 psi to run, you will need a regulator to turn down the psi if the pump you buy has more. I had the same issue with my jeep not starting if left more than a day, actually over night. Not sure which part cured it but I replaced the coil, points and condenser and problem solved.
     
  3. Jan 13, 2014
    timgr

    timgr Jeepin' Nerd 2020 Sponsor 2019 Sponsor

    Medford Mass USA
    Joined:
    Aug 10, 2003
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    20,581
    Electric pump is fine, if that's what you want.

    Mechanical pumps work fine if you have no air leaks between the tank and the pump, the plumbing is not clogged somehow, and the pump is in good condition. Mechanical fuel pumps are very reliable generally, and a new, brand name pump will last a long time.

    The Motorcraft carburetors tend to dry out rather quickly if the car sits for any length of time. That's not a problem with the fuel pump, but an electric pump can be used to "cure" the problem.

    This topic has been covered ad nauseum in the past. Here's a search that should give you plenty of reading: https://www.google.com/search?q=site:earlycj5.net+electric+fuel+pump
     
  4. Jan 13, 2014
    Corveeper

    Corveeper Member

    Chanute, Kansas
    Joined:
    Jul 29, 2005
    Messages:
    817
    http://kmjent.com/index.php/catalog...fuel-pump-140gph-universal-fit-3-8-npt-ports/

    I’ve had pretty good luck with KMJ Performance and the parts I’ve gotten from them but really this same type of pump is available from a variety of sources. It’s basically a knock off of a Holley Blue pump. It does run high pressure for a carburetor, 14 psi, so a regulator and gauge would be needed to regulate that pressure down to under 7 psi. And when you’re looking at these things remember the flow rate they advertise is free flow, make it push pressure and that flow rate can drop by around 30-40%.
     
  5. Jan 13, 2014
    Jeepenstein

    Jeepenstein Me like Jeep..

    Middle TN
    Joined:
    Jun 15, 2003
    Messages:
    1,678
    My CJ always ran a cheap-o in line electric and I never had an issue..
     
  6. Jan 14, 2014
    johneyboy03

    johneyboy03 The green beast

    Quebec, Canada
    Joined:
    Jan 15, 2011
    Messages:
    1,761
    I'm thinking too about adding a electrik pump. During winter on cold condition when i'm a week without using the jeep it's very long cranking before engine start. But asap that engine has started i get no problem.

    It there a way to use both? only use electric on initial start-up and keep the mechanical for normal operation?
     
  7. Jan 14, 2014
    Corveeper

    Corveeper Member

    Chanute, Kansas
    Joined:
    Jul 29, 2005
    Messages:
    817
    I know that a Mr. Gasket pump can be drawn through like you’re talking about because I’ve done it.
    Set it up with a momentary switch and use it strictly for priming the carb.
     
  8. Jan 14, 2014
    timgr

    timgr Jeepin' Nerd 2020 Sponsor 2019 Sponsor

    Medford Mass USA
    Joined:
    Aug 10, 2003
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    My CJ-6 came to me with a Mr. Gasket pump on the left front inner fender, exactly for that purpose. Sounded like someone hammering on the fender when it was running.
     
  9. Jan 14, 2014
    johneyboy03

    johneyboy03 The green beast

    Quebec, Canada
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  10. Jan 14, 2014
    Corveeper

    Corveeper Member

    Chanute, Kansas
    Joined:
    Jul 29, 2005
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    817
    I would have to look when I get home to be sure but it looks like the 12S pump.
    Basically its what was available at O'Reilly at the time.
     
  11. Jan 14, 2014
    sterlclan

    sterlclan Member

    exploring the...
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    Feb 21, 2009
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    3,209
    as a primer id use the other one 42s. if planning on using the original mechanical pump too no need for the additional pressure offered by the 12s
     
  12. Jan 15, 2014
    jeepcj

    jeepcj Member

    cincy, Ohio
    Joined:
    Aug 23, 2009
    Messages:
    601
    I think mine is the 12s also, i'll have to go outside this morning as soon as it gets daylight and see. Mine also was at my local auto store, just make sure you get one for a v8,, I got the 4, 6 cyl pump the first time and it didn't last long, probably half the summer.
     

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