Working on a fuel issue

Discussion in 'Street/strip 400/430/455' started by rkammer, Aug 5, 2018.

  1. rkammer

    rkammer Gold Level Contributor

    I'm pretty sure my 455 is running out of fuel when I punch it and go to all four barrels or, in the long 3rd gear push past about 80 MPH. The engine just noses over and quits running. If I let off the gas it recovers and smooths out. I'm running a Mark Northcutt built Quadrajet, stock Stage 1 fuel pump, and stock fuel lines back to the tank. I have the return line blocked. My build is below my signature.

    So, I want to start by checking fuel pressure when the problem shows up by running a fuel pressure gauge from the original steel line going from the pump to the carb and monitoring it at the windshield. What's the best method for doing this? I don't mind cutting the fuel line since I'll be installing an inline filter anyway and removing the one at the carb.

    And, what fuel pressure should I be seeing under normal and hard acceleration?
     
  2. Schurkey

    Schurkey Silver Level contributor

    Ideally, you'd be looking for an inverted-flare Tee. Straight-through whatever size your existing fuel tube is (5/16 or 3/8) with a branch that's either pipe-thread or smaller inverted flare. Use the branch to plumb in tubing or hose adapters to supply pressure to the gauge.

    Cut and double-flare the tubing to suit the Tee. When you're done checking pressure, you'd probably have to cut one of the flares off and re-flare that side of the tubing to allow for the longer fuel filter. If you're lucky, you'll find a fuel filter that has the same size inverted flare as the Tee.

    OR

    Use the blocked-off fuel return fitting to plumb the pressure gauge to. The restriction in the fuel pump for the return fitting may dampen the gauge more than optimum, but it could still work.
     
    rkammer likes this.
  3. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

  4. rkammer

    rkammer Gold Level Contributor

    The blocked off fuel return sounds like the simple way if it works. But, under hard acceleration wouldn't the return line be next to no pressure even if the pump was supplying the correct pressure?
     
  5. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

  6. rkammer

    rkammer Gold Level Contributor

    That looks like the way to go then, I can just install the filter after I'm done checking pressure. What kind of flare should I make after cutting the steel fuel line for both the gauge fitting and the fuel filter after that? Can you recommend a pressure gauge that's properly damped and reasonably priced if there is such a thing? I'll post results after I get everything rigged up.
     
  7. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

  8. Briz

    Briz Founders Club Member

    The Riv was doing just that at any RPM over 4000. Ended up running 1/2 line and Robb Mc 550 HP mechanical pump. No problems since
     
  9. rkammer

    rkammer Gold Level Contributor

    Is that Robb MC pump a bolt-in? The arm matches up with the cam?
     
  10. CJay

    CJay Supercar owner Staff Member

    Normally, Im all for diagnosing a problem before just "throwing" parts at it, but isn't a fuel pump like $30? If its been in there a while, just chuck one in and see if it works
     
    rkammer likes this.
  11. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    The 550 pump is a bolt in. It has a Buick arm.
     
    Briz likes this.
  12. 1973gs

    1973gs Well-Known Member

    Just disconnect the line at the carb, slip on a piece of fuel line with a "T", and connect it to a short piece of fuel line with the proper fitting for the carb. Make sure to install hose clamps at all of the connections. This is only temporary, but with this setup, you should be able to tape the gauge to the windshield and drive the car. If I remember, pressure should be above 4 1/2 lbs. When you take off the line, before you hook up the gauge, put the hose into a container and crank the engine.. It should pump 1 pint in 30 seconds. Make sure that the hose from the tank sending unit to the steel line isn't cracked. I've seen cracked hoses suck air but not leak any fuel. I don't recommend replacing the pump unless it 's bad because the new Chinese pump will probably fail sooner than the old pump that's in the vehicle now.
     
  13. redbuick

    redbuick Well-Known Member

    Your running 12.90's with a q-jet, I don't think fuel pressure is your problem, I'd be looking at ignition problems. Why do you have your return blocked at your power level?
     
  14. 1973gs

    1973gs Well-Known Member

    I'm guessing that the car has developed a problem and probably won't run 12's right now.
     
  15. rkammer

    rkammer Gold Level Contributor

    That's correct. The high 12s were run about two years ago and would go through the 1/4 clean. This problem has developed gradually over the past year or so.
     
  16. Bens99gtp

    Bens99gtp Well-Known Member

    If it's running hard up till top of 2nd or bottom of 3rd gear, then lay over, but pick up again if you back off for second it's fuel not ignition. Assuming no internal carb changes made like jets or float level. If not it's fuel volume
     
    rkammer likes this.
  17. rkammer

    rkammer Gold Level Contributor

    That's exactly what it's doing.
     
  18. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    When I went to the aluminum heads, I knew the Stage 1 pump would not keep up. I simply feed in a Holley Red pump in the rubber fuel line in front of the tank. I ran it with a switch and relay. It served me well until my current engine when I went with the CV products pump. What I found is that the Holley presented a restriction when off. I had to switch it on when I wanted to play. You can wire a relay to the kick down switch to turn it on that way. The Holley acts as a pusher to the Stage 1 pump, simple and effective.
     
  19. Rich Johns

    Rich Johns Platinum Level Contributor

    Hi Larry
    What do these pumps look like and where is source to buy?
     
  20. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

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