Fuel pressure drop ?

Discussion in 'The Mixing shop.' started by DEADMANSCURVE, Oct 5, 2017.

  1. DEADMANSCURVE

    DEADMANSCURVE my first word : truck

    65 special , 350
    Stock tank cleaned , gas cap on , redone stock pickup/sender assy ( now 3/8 ) installed - so sealed basically . New 3/8 metal line to new fram canister filter , new line to new Carter mechanical strip pump , rubber hose up to new Holley #12-803 regulator and new jegs gauge , rubber hose to Qjet .
    So , start motor , gauge goes right up to #7 , runs fine .
    After warm-up , say 5 minutes maybe , gauge slowly drops to #3 , runs fine ?
    Filter ? Reg ? Gauge ? Voodoo ?
    Any ideas appreciated .
    Thanks
     
  2. Bens99gtp

    Bens99gtp Well-Known Member

    Is it an oil filled gauge.......if so when the oil warms up the pressure will show a drop, even though it did not drop. But the only way to truly verify is get another gauge and see if it matches.
     
  3. DEADMANSCURVE

    DEADMANSCURVE my first word : truck

    it is a liquid filled gauge .
    I got it for vibration reasons , it is nice n steady . do you know why the oil fill acts that way ?
     
  4. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD"

    The gauge gets hot and the reading changes. Try running a hose out the back of the hood and tape the gauge to the windshield. then drive the car.
     
  5. Bens99gtp

    Bens99gtp Well-Known Member

    They act this way cause the fluid they fill it with changes viscosity. Kind of like why your oil pressure is higher at cold start than it is when warm.

    Simple solution put a not fluid fill gauge on. I run an electric sender for this reason, plus u can have the gauge inside the car with no fear of flammable fluid to leak.
     
  6. DEADMANSCURVE

    DEADMANSCURVE my first word : truck

    car not on road yet .
    its on a bracket on front of left cyl head so the vibration aspect sounded interesting . no real money dif .
    maybe they are meant more for a fenderwell mount , something not quite so close to heat ?
    i'll grab a new gauge shortly , see how it goes .
    yes an interior gauge i've thought about .
    thanks .
     
  7. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD"

    Mechanical fuel pumps get hot, and the pressure can become somewhat uneven. My CV pump normally puts out between 8 and 9 psi at idle and going down the road. If I get stuck in prolonged stop and go traffic in hot weather, the pressure drops off, sometimes as low as 4 psi. As soon as I get clear and back up to speed, it pops back up to 8-9 psi. This as measured by an Autometer electric gauge.

    GaugeReadingsHot.JPG GaugeReadingsHot.JPG
     
  8. DEADMANSCURVE

    DEADMANSCURVE my first word : truck

    larry - actually have the same 3 sport comp gauges under my dash . was just checking out a similar matching pressure gauge today . sender part # ? or can you get the gauge n sender in a kit of some sort ?
     
  9. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD"

  10. DEADMANSCURVE

    DEADMANSCURVE my first word : truck

    thanks .
    yes , matches nicely . i like the gauge and sender coming together , less problems .
    picked up a cheap basic gauge for now . the auto meter budget-buster will be later !
     
  11. Bens99gtp

    Bens99gtp Well-Known Member

    Our car, it's sees 0 street time has a Barry grant 280 electric pump with a return regulator, set at 8 psi, the only time it ever moves from this number is when the level in the tank gets low and the fuel starts to get air bubbles in it........other than that I can leave the pump on and it never moves. With the return regulator the pump doesnt get too warm either. Set many street cars up with the same setup just a smaller pump.
     

Share This Page