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Hot Rods Fuel question ?

Discussion in 'The Hokey Ass Message Board' started by mark hogan, Aug 20, 2025 at 11:22 AM.

  1. mark hogan
    Joined: Jul 27, 2022
    Posts: 146

    mark hogan
    Member

    Folks looking for more ideas. I’ve been chasing the tail on this one. 30 coup running stock tank, stock ball valve at bottom of tank and stock piping to stock full bowl. Alls been updated and restored. Stock hard line down past floor board the to rubber line to fuel pump. Rubber line out of pump to hard line on fire wall to regulator the two clear fuel filter to fuel rail. Car runs great gage reads 2 psi. Then shell starve for fuel. I get out as it’s running and gage reads 0 for a few then gos to 2psi and noticing very little fuel going through clear filter at fuel rails??? I’ve changed pump which did nothing. Played with regulator and at this time the adjustment is full open! So pump delivers 2psi which that’s max on these carbs. I’m running 3. I’ve got all new filters. You can here pump run. What do you all think. Kinda hard to roll out always wondering about fuel. Thanks all ideas welcome at this point! I must be missing something here. Good Day!!
     
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  2. Joe Blow
    Joined: Oct 29, 2016
    Posts: 1,681

    Joe Blow
    ALLIANCE MEMBER

    What's the make of your regulator?
     
  3. mark hogan
    Joined: Jul 27, 2022
    Posts: 146

    mark hogan
    Member

    Japanese / Chines have not found a quality one .(speedway)
     
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  4. Retterath
    Joined: Oct 25, 2020
    Posts: 6

    Retterath

    Try without the filters. I've recently had 2 Napa gold filters that actually collapse when I turn the pump on.
     
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  5. Joe Blow
    Joined: Oct 29, 2016
    Posts: 1,681

    Joe Blow
    ALLIANCE MEMBER

    Like a Mr. Gasket? Could be your problem....look at a low pressure Holley.
    thumbnail (89).jpeg
     
  6. mark hogan
    Joined: Jul 27, 2022
    Posts: 146

    mark hogan
    Member

     

    Attached Files:

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  7. mark hogan
    Joined: Jul 27, 2022
    Posts: 146

    mark hogan
    Member

    I’ve got the fuel bowl filter it’s new bowls clean. Micron filter at pump which is large screen. Bowl always has fuel in these episodes? It runs well for longer drives but at some point will act up cold or hot..
     
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  8. Joe Blow
    Joined: Oct 29, 2016
    Posts: 1,681

    Joe Blow
    ALLIANCE MEMBER

    Speedway's knock off of a Holley.....but then again the Holley's quality is starting to lag too (overseas). I'd sure look at that regulator though.
     
  9. Doublepumper
    Joined: Jun 26, 2016
    Posts: 1,763

    Doublepumper
    Member
    from WA-OR, USA

  10. mark hogan
    Joined: Jul 27, 2022
    Posts: 146

    mark hogan
    Member

    Model a fuel caps have never seal well. Thanks for the help
     
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  11. TCTND
    Joined: Dec 27, 2019
    Posts: 715

    TCTND
    Member

    That really does sound like an unvented tank; ask me how I know. Try leaving the cap loose for a while and see if anything changes. If the vent is blocked you'll notice it more quickly when the tank is full than when it's low.
     
  12. 19Eddy30
    Joined: Mar 27, 2011
    Posts: 3,483

    19Eddy30
    Member
    from VA

    If using stock fuel tank in cowl
    Should Not need a fuel pump ,
    Should have No issue Gravity feeding carburetors Unless there is a restriction
    1 gal fuel weight 6 pounds ish ,
    Experiment with a jet and fuel supply line so does not over come needle and seat when gravity feeding.
    I have been having issues with the
    Clear plastic fuel filers shown lately ,
    Napa & Autozone . On 5-25 hp small engine's.
    Japan part's better Quality than cheap China,
    Aeromotive make's Quality fuel regulators and pumps
     
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  13. Fuel ehh? Whatta gas! Hehe.
     
  14. mark hogan
    Joined: Jul 27, 2022
    Posts: 146

    mark hogan
    Member

    On my test run I used gravity feed. In was proven unstable to provide consistency on Tri-Power big 97s. It would allow max of 19/2000rpms. Then starve ? Firewalls to close for mechanical pump system. Thank you for the ideas.
     
  15. mark hogan
    Joined: Jul 27, 2022
    Posts: 146

    mark hogan
    Member

    My fuel cap sorta rattles if to full on roughy terrain it slops out. Venting not an issue. Thanks for the help.
     
  16. mark hogan
    Joined: Jul 27, 2022
    Posts: 146

    mark hogan
    Member

    Just received a new Hollie from S-way the mounting hole were not tapped?? Go figure. Three day out from test run I’d say.
     
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  17. winduptoy
    Joined: Feb 19, 2013
    Posts: 3,997

    winduptoy
    ALLIANCE MEMBER

    Mark,
    I agree with you and your need for a fuel pump...that works.
    I lean towards the regulator as well but this is a shot gun approach...
    Zero pressure on the gauge should be a clue....but since it is on the outlet/regulated side you don't know if it is the regulator or the pump....if you had a gauge on the inlet to the pump, that might tell.
    I use a Holly 12-426 fuel pump to 2ea, 97 carbs on the 12V banger and it doesn't require a regulator. It has been good to me. The 6V banger has a Facet pump that has been problematic, you could hear it running but it didn't pump. I recall replacing it and it is now on it's third one in 15+ years
    I use a Malpassi fuel pressure regulator and I like it because it looks more era appropriate and it works flawlessly.
    https://www.heritagepartscentre.com...MIxvjBqqeajwMVY7IDAB2yWyyuEAQYASABEgLTvvD_BwE
    follow the link or queri under Malpassi fuel pressure regulator....
    good luck
     
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  18. BJR
    Joined: Mar 11, 2005
    Posts: 11,087

    BJR
    Member

    Is the tank clean? I had a piece of teflon tape floating around in a tank once. Everyone in a while it would get sucked up against the fuel line in the tank and block the fuel. When the suction stopped it would fall off and all was well again until next time.
     
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  19. Joe Blow
    Joined: Oct 29, 2016
    Posts: 1,681

    Joe Blow
    ALLIANCE MEMBER

    Good luck man.
     
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  20. deucemac
    Joined: Aug 31, 2008
    Posts: 1,639

    deucemac
    Member

    I had a customer one time that had fuel starvation problems. Turned out that he had an unvented cap and the fuel leaving the tank eventually cause a vacuum and caused the starvation! He was pulling his hair out in frustration. We recommended a vented cap, and voila! Problem cured!
     
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  21. Doublepumper
    Joined: Jun 26, 2016
    Posts: 1,763

    Doublepumper
    Member
    from WA-OR, USA

    ^ This reminds me of.
    In the early eighties Harley Davidson started using a smog cap on some FX and XL models. It was a vented cap, but it was controlled by a spring that would open at a certain vacuum, and pressure. Problem was the vent wouldn't always open to vent as it should. Get much above sea level and they would stay closed, causing the fuel to stop. It was a source of lots of confusion. The engine would act like it was out of fuel...the rider would open the tank to check...nope, plenty of fuel. In the process of checking the fuel the vacuum in the tank was relieved. The rider would fire up his scooter and ride off...only to have it happen again...and again...and again.
     
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  22. mark hogan
    Joined: Jul 27, 2022
    Posts: 146

    mark hogan
    Member

    I’ve drove the car quite a bit when it was stock model A never had an issue till now so kinda raises your brow.. I’m going to take a look inside the tank. Thanks
     
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  23. clem
    Joined: Dec 20, 2006
    Posts: 4,617

    clem
    Member

    If none of the above recommendations help, which I believe they will,
    perhaps consider whether the diameter of the stock lines ( I am not familiar with Model A) are possibly insufficient size for 750cfm carbs at 2lb pressure ?
     
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  24. 19Eddy30
    Joined: Mar 27, 2011
    Posts: 3,483

    19Eddy30
    Member
    from VA

    @mark hogan
    I believe A tanks have a debris collecting
    Area right in side tank Outlet .
    I believe As where 3/8 I.D. Hole .maybe 7/16 ?
    Try borescope if you have.
    Some vent caps Vent to small ,Vacuum restriction , but sure you tried with out cap . There must be a restriction @ tank outlet, @ ball valve
    Feral , @ carbs inlets, ext.
    Typical F-H lucky if 100 hp , not that much fuel consumption.
    Facet Brand makes good low pressure
    fuel pumps .
    The / those small low pressure gauges below 10 psi , size of 50 Cent piece
    Are not accurate, The smaller the gauge the internals are just to small for the precise mechanism needed,
    I have called / email many top Manufacturers In Industrial & common gauge manufacturers Brands .USA & European.
     
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  25. clem
    Joined: Dec 20, 2006
    Posts: 4,617

    clem
    Member

    Maybe I missed it, but OP never stated type of engine, so how do you know that it is a flathead ?
     
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  26. Budget36
    Joined: Nov 29, 2014
    Posts: 15,054

    Budget36
    Member

    Post number 6, you can see it’s a FH.
     
  27. 31 Coupe
    Joined: Feb 25, 2008
    Posts: 505

    31 Coupe
    Member

    Clem beat me to it ..... if the gravity feed volume straight to the carbs was insufficient maybe the supply line between the tank outlet and the pump inlet can't cope too and it's cavitating.
    Maybe experiment with a larger diameter hose going between the pump inlet and into the top of the tank filler neck ..... just to isolate that aspect of the problem.
    Good luck.
     
  28. clem
    Joined: Dec 20, 2006
    Posts: 4,617

    clem
    Member

    thanks @Budget36 , don’t think those pictures loaded when I initially read this thread - poor internet connection today !
     
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  29. mark hogan
    Joined: Jul 27, 2022
    Posts: 146

    mark hogan
    Member

    it was a thought to me also at build time. Seems I’ve driven long distance 55 or so miles before taking a break with out a hiccup. Then when it starts it’s random. Soon I’ll have a new regulator on and inspect fuel tank from neck. So if lines work for a long Strech at Hwy speeds 2500-2900 Rpm I’m thinking my problem lies in the murks of the unknown !
     
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  30. mark hogan
    Joined: Jul 27, 2022
    Posts: 146

    mark hogan
    Member

    I had that thought also? I’m running second Facet pump figured it was pump? Then opened the fuel regulator to max it read 2 1/2 -3 pounds psi. So I’ve ran the regulator wide open no restriction. It was so close to what I wanted. I’ve had zero seepage or flood issues.
     
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