Fuel pressure regulator Q's

Discussion in 'The Mixing shop.' started by BUICKRAT, Mar 28, 2019.

  1. hugger

    hugger Well-Known Member

    I'm sure you know this but if using a liquid filled gauge it will show a false drop in psi after you get it to good operating temp. A standard gauge will keep its position albeit bouncing everywhere...
     
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  2. Cliff R

    Cliff R Well-Known Member

    +2

    A liquid filled gauge will not show correct pressure if mounted under the hood in the heat.

    High output/high pressure mechanical pumps can cause issues if ran "dead-head". I would imagine this happens because of the design (valves opening/closing with engine speed). I tried one briefly attempting to solve some fuel delivery issues at the track and it kept flooding on the street on hard stops and sometimes cornering.

    They advertise a lot of these electric pumps to be fine ran "dead-head", but I've had much better success running them with a return to take some load off the pump when demand is low (normal driving).

    Case in point. When I first went to an sumped tank, 140GPH electric pump a behind the tank and 8AN lines/fittings everyplace I ran it thru a Holley regulator with no return. It worked fine but FRIED the pump in about a month of street driving.

    I added a bypass with no other changes, the second pump lasted from 2000 till about a year ago and required brush replacement. Lets see, 2 months and fried the brushes vs 18 years.......I think it liked the bypass system just a little better than the "dead-head"........Cliff
     
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  3. Electra Bob

    Electra Bob Well-Known Member

    I'm installing a Sniper Quadrajet EFI system on the Electra with an in tank pump and a regulator on the return side.

    The regulator has a manifold vacuum reference port that will drop the pressure at idle and cruise. This should help take the strain off the pump under most driving conditions.

    Bob
     
  4. BUICKRAT

    BUICKRAT Torque Rules!

    I was not aware of that. My gauge is liquid filled. I will check that thanks.
     
  5. Bens99gtp

    Bens99gtp Well-Known Member

    yes it's well known if you set pressures with a cold/cool oil/liquid filled gauge it will read correct. once the under hood temps get up to running conditions the liquid thins out and normally the pressure shows a drastic drop.

    the liquid is used to keep the needle from bouncing......this is why if I can I only use non liquid but prefer and electrical gauge
     
    Last edited: Apr 17, 2019 at 10:11 AM
  6. Electra Bob

    Electra Bob Well-Known Member

    Are you saying a liquid filled gauge only reads correctly when hot?

    I would think the only effect of heating would be a thinning of the damping liquid and a more bouncy reading. If there is a pressure drop when hot would that not be due to an actual pressure drop in the system being measured?

    Bob
     
  7. Electra Bob

    Electra Bob Well-Known Member

  8. Bens99gtp

    Bens99gtp Well-Known Member

    no it reads off when warm, the fluid creates the resistance in the reading. when warm it changes and becomes NOT accurate
     
  9. Electra Bob

    Electra Bob Well-Known Member

    From the link I gave my impression is that the warming of the liquid increases the pressure inside the gauge and that works in opposition to the measured pressure resulting in a lower reading.

    Apparently there are liquid filled gauges that have a small valve allowing for internal to ambient pressure equalization.
     
  10. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD"

    Cliff, I guess I have been lucky with the CV mechanical pump I got from Jim Weise. Been using it for 7 years now without a problem. Neither my Quadrajet nor my AED 1000 HO seems to have a problem with the normal 8-9 psi it makes. It has never flooded either carburetor and most of my driving is street driving. Just my experience with that particular pump.
     
  11. Cliff R

    Cliff R Well-Known Member

    I went to an electric pump around 2000 and never looked back. It immediately solved all my fuel delivery issues. With the mechanical pump I was still sucking the bowl low on hard runs. Even put my big Holley 4781-2 in place and had problems running it low. The electric pump mounted behind the tank proved to be superior to the engine mounted mechanical pump, haven't had the first hint of a fuel delivery issues since.......Cliff
     

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