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 Pump Recommendations?

Discussion in 'Early CJ5 and CJ6 Tech' started by jbjeeps, Jul 24, 2022.

  1. Jul 24, 2022
    jbjeeps

    jbjeeps Member 2022 Sponsor

    The Idaho side...
    Joined:
    Jun 12, 2010
    Messages:
    527
    Our ’53 M38A1 has the stock F head engine, stock YS 950 carb and is converted to 12 volts.

    The Airtex 572 fuel pump I put on about 7 years ago is only putting out 2 - 2 1/2 pounds of pressure according to the Holley fuel pressure gauge I have mounted just before the carburetor.

    I sent the carburetor out to be professionally rebuilt about a year and a half ago. It has very little use on it since then. The pressure spec on this carb is 4 1/2 - 5 pounds.

    I’ve tried some of the less expensive generic replacement fuel pumps. Not good.

    I don’t have vacuum wipers, so I don’t necessarily need a pump for them. But I'll put one on if that's the best available.

    My questions are:
    1. What mechanical fuel pump do you recommend that will give me the 4 1/2 - 5 pounds?
    2. What electric fuel pump do you recommend? Will it require a pressure regulator?

    Thanks, Jack
     
  2. Jul 24, 2022
    Glenn

    Glenn Kinda grumpy old man Staff Member

    Apopka, Fl
    Joined:
    Sep 21, 2002
    Messages:
    12,036
    Isn't the 4 1/2 lbs. maximum pressure? Are you saying yours is not delivering enough gas to the carb?
     
  3. Jul 24, 2022
    PeteL

    PeteL If it wasn't for physics, and law enforcement... 2022 Sponsor 2021 Sponsor

    Hills of NH
    Joined:
    Aug 3, 2003
    Messages:
    8,852
    Maybe an OEM military pump would suit your carb. Expensive, but super-duty.
     
    scoutpilot likes this.
  4. Jul 24, 2022
    Keys5a

    Keys5a Sponsor

    Florida Keys
    Joined:
    Jan 23, 2014
    Messages:
    3,793
    Rebuild your fuel pump. Kits are available. Most likely the rubber diaphragm has a small hole or tear, or a piece of dirt is under one of the check valves.
    -Donny
     
    jbjeeps likes this.
  5. Jul 25, 2022
    jbjeeps

    jbjeeps Member 2022 Sponsor

    The Idaho side...
    Joined:
    Jun 12, 2010
    Messages:
    527
    The TM 9-8014 lists the pressure as 4 1/2 - 5 lbs at 1800 rpm. Yes, I'm thinking the carb isn't getting enough fuel.
     
  6. Jul 25, 2022
    jbjeeps

    jbjeeps Member 2022 Sponsor

    The Idaho side...
    Joined:
    Jun 12, 2010
    Messages:
    527
    I need to look into that. I think I may actually have an original pump, I just need to find it. :) If nothing else it could be a good core.
     
  7. Jul 25, 2022
    Rick Whitson

    Rick Whitson Detroit Area 2022 Sponsor 2021 Sponsor

    I live South of...
    Joined:
    Dec 2, 2014
    Messages:
    1,590
    On both my F 134's I used the one with the inverted glass bowl, they both run well.
     
  8. Jul 25, 2022
    PeteL

    PeteL If it wasn't for physics, and law enforcement... 2022 Sponsor 2021 Sponsor

    Hills of NH
    Joined:
    Aug 3, 2003
    Messages:
    8,852

    Me too. But I think they may be specc'ed for the YF carb which prefers 2.5 to 3 psi.

    And I just paid $100 for a rebuild kit. :shock:
     
  9. Jul 25, 2022
    timgr

    timgr We stand on the shoulders of giants. 2022 Sponsor 2021 Sponsor

    Medford Mass USA
    Joined:
    Aug 10, 2003
    Messages:
    23,605
    I would point out - your Jeep will run from a gas can sitting on the cowl, powered only by siphon pressure. BTDT. A meter of water is only 1.5 psi, and less than half that distance of a less dense fluid should be ca 1/2 psi. 2.5 psi from the pump is plenty to run the engine.

    [​IMG]
     
    Last edited: Jul 25, 2022
    jeepstar likes this.
  10. Jul 25, 2022
    DirtRoad61

    DirtRoad61 Member

    California
    Joined:
    Jun 9, 2019
    Messages:
    50
    I've been using the Edelbrock mico pump for a few years. I have a solex carb and don't need a pressure regulator on mine.
     
  11. Jul 26, 2022
    Rick Whitson

    Rick Whitson Detroit Area 2022 Sponsor 2021 Sponsor

    I live South of...
    Joined:
    Dec 2, 2014
    Messages:
    1,590
    Most Motorcycles don't have fuel pumps, rely on gravity to feed the carburates.
     
  12. Jul 28, 2022
    Jw60

    Jw60 It's not flat, it's aired down. 2022 Sponsor 2021 Sponsor

    Sedalia MO.
    Joined:
    Apr 8, 2008
    Messages:
    3,264
    The pressure would really only apply to the needle and float. after that there is no pressure in the bowl unless some fool put a Turbo on it... :whistle:

    Check flow from the pump by putting the carb inlet hose into a container. A length of clear hose would allow you to see any bubbles. Are there any spacers under your pump against the block? Is the cam and pump foot in good condition?
     
    Rick Whitson likes this.
  13. Aug 2, 2022
    jbjeeps

    jbjeeps Member 2022 Sponsor

    The Idaho side...
    Joined:
    Jun 12, 2010
    Messages:
    527
    Update: finally had a chance to check through my boxes, found an original M38A1 fuel pump, sent pictures to the supplier who confirmed it is a good core, so I've ordered a rebuilt original M38A1 fuel pump. I'll let you know how that turns out. Thanks again to those who have contributed. Jack
     
    Dwins1 and Jw60 like this.
  14. Aug 24, 2022
    jbjeeps

    jbjeeps Member 2022 Sponsor

    The Idaho side...
    Joined:
    Jun 12, 2010
    Messages:
    527
    Update #2:

    “Most carburetor problems are electrical.”

    There’s more than a little truth to that old statement.

    The newly rebuilt original military style fuel pump is in. It’s a great looking piece, nicely done, and has worked flawlessly since the first turn of the key. I’m glad to finally have the correct pump in place. It goes well with the original military YS-950 carburetor Scoutpilot rebuilt for us a while back.

    Both those jobs were overdue, but the old A1 still wasn’t running as well as I knew it could.

    We converted to 12 volts years ago. There’s no timing marks on the front of the engine, so I used the vacuum timing method that Scoutpilot recommends on his web page. It took me a few tries, but the A1 is now back to it’s former self, running well and ready for the trails once more.

    I’ve decided to give Pertronix a try, so I’ve ordered one of those kits. It’ll be here next week.
     
    Last edited: Aug 24, 2022
    Fireball and jeepstar like this.
  15. Aug 24, 2022
    jeepstar

    jeepstar Well-Known Member 2023 Sponsor 2022 Sponsor 2021 Sponsor

    Sheboygan
    Joined:
    Jun 28, 2006
    Messages:
    2,393
    I did this year's ago, haven't looked back. Still keep the points and condensers and all that in a bag in the under seat tool box, but they are probably rusty by now, thinking about it.
     
    Last edited: Aug 24, 2022
    jbjeeps likes this.
New Posts