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...
    BUICKRAT likes this.
  2. Cliff R

    Cliff R Well-Known Member


    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.


    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
  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?

  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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