Electric fuel pumps

Engine, Transmission & Driveline

  1. ideologist

    ideologist Member

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    Mar 8, 2020
    Bay Area, CA
    Is there a benefit to replacing the stock fuel pump with an electric pump?
  2. saylor

    saylor Senior Member

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    Mar 31, 2013
    yes, but there is a drawback too. mechanical pump only depends on the motor turning to function. electric pumps take more, obviously with wire and elec and all that. and you need to add some safetys, so its more complicated than a mechanical pump too.

    now - why you DO want to do it.

    go to whataburger and buy a good thick vanilla shake.

    OK - pretend the shake is your gas tank, full of nice cold vanilla gas.

    put the straw in, thats your fuel line.

    give it a good suck. The straw collapses, and you get no shake.
    now lift the straw up so some air can get it.
    it just kind of gurgles, and you still get no shake.
    thats the mechanical pump.

    now take the straw out.

    BLOW thru the straw.
    now you got vanilla shake everywhere.
    thats the electric pump.

    basically, with negative pressures, you collapse hoses, if any air gets in the line it quits working, etc, etc. you could imagine that if the tank was airtight sealed, the vaccuum would overpower your suckage, and you will quit getting shake, or you will collapse the cup (tank) from sucking too hard. or collapse a feed line (your straw).

    with positive pressures, you avoid all that.

    another thing is fuel has a WAY harder time (or any liquid) vaporising under positive pressure. so vapor lock doesnt happen anymore. another another thing is air cant get trapped anywhere as it will be expelled under pressure.

    but you need a fuse on the power supply. you need to operate it with a relay. you need a fuel shut off pressure switch. you can also put in a rollover siwtch out of a tarus.

    i wrote up a write up somewhere in this forum about how to do it.

    try not to die -

    - saylor
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  3. CBODY67

    CBODY67 Old Man with a Hat

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    Mar 27, 2011
    One reason that electric fuel pumps are usually mounted at/near/in the fuel tank is to minimize the "negative pressure area" of the fuel lines (i.e., length of the lines). Which can impact things like "vapor lock" in hot weather conditions. Negative pressure lowers the vaporization temp of the raw fuel, so it can "boil" in the lines before it might get to the pump. Resulting in no liquid fuel getting to the carb.

    An electric fuel pump can be set to a particular pressure setting, whereas a mechanical pump has a range of pressures, depending upon engine speed. Volume will be less variable, too. Further, a fuel pressure regulator can fine-tune delivery pressure, if needed.

    The electric fuel pump will NEED some manner to turn it off in the case of the engine not running. Earlier ways were to wire it through an oil pressure switch on the engine. Later ways were, with fuel injection, to run it through a timer to disconnect the battery feed if the engien didn't start within a certain amount of seconds. Not to forget the inertia switches (as in many earlier EFI Ford vehicles), to cut power to the pump in the case of an impact/accident.

    A properly-designed mechanical pump fuel system can work well and supply massive amounts of horsepower, if correctly-sized and engineered. But a "serious" performance vehicle used to always have an electric pump mounted near the rear axle ares of the floor pan. That distinctive "hummmm" meant there was a serious engine under the hood.

    A more common reason for an electric "booster pump" was to help prevent vapor lock in hotter climates. Chrysler used one in some earlier '70s CA-spec Imperials, I believe. The parts book details that particular installation in the illustrations of the Imperial fuel system, that model year. Other means of helping control vapor lock included having a "return line" from the fuel filter/separator to keep fuel moving in the fuel lines at all times. An orifice in the fuel filter less excess fuel return to the tank, into a separate return line.

    Some might, in more recent times of limited use vehicles and ethanol'd fuel, desire to replace their mechanical fuel pump with an electric one. No rubber diaphram to be damaged by ethanol fuel. But as ethanol attracts moisture, the fuel can have a bit of moisture in it which can tend to degrade the vanes in a "vaned" electric fuel pump. OEM "in the tank" or an accessory "add-on" unit. Which might be one reason that many OEMS have changed to a "gear-type" pump ranter than a "vaned" pump mechanism?

    In many cases, an electric fuel pump is not needed for nice vehicular operation. But, as mentioned, having a well-designed electrical supply system to power the pump IS necessary. Which might be more to execute than some might desire. Things to consider . . . Your judgment call.

    Just some thoughts,
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  4. Oz Sport Fury

    Oz Sport Fury New Member

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    Sep 5, 2020
    Canberra Australia
    My 69 Phoenix (Fury 4dr in my pic) I had a Holley Blue pump fitted with a LPG roll over/engine cutout relay fitted, ABSOLUTE BEST THING I did to the car at that time, as the car sits for long periods, I connect the battery isolator with the green knob, turn the key, wait for the pump to finish priming and fill the carby bowls, 2 squirts on the peddle, roll the key and she would fire up after sitting for a couple of months, so happy with that set up at the time. Highly recommend it. Good luck finding a late model car with a mechanical pump also.
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  5. Big_John

    Big_John Illegitimi non carborundum FCBO Gold Member

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    May 21, 2013
    Marcellus, NY
    IMHO, the only good reason to replace the stock pump with an electric is that your car requires more fuel flow than a stock pump can put out.

    In street use, I believe, based on my experience with add-on electric pumps, the stock pump will be more reliable than the electric.

    What I did on my car to aid in start ups after sitting, was to add a cheap flow through type pump back by the tank. I have a monetary contact toggle switch under the dash, with a relay under the rear seat. I hit the toggle to prime the carb, and once it fills the carb (the sound changes in the pump), I start the car and never touch it again.

    For me, this is the best of both worlds. A reliable stock pump, with a priming electric pump to start the car after it's sat for a couple weeks.
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  6. adamlien

    adamlien New Member

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    Sep 16, 2020
    this happened on my friends 440 motor home.. went electric because of vapor lock issues.. cold start and stall after 15 seconds requiring lots of cranking to get it to restart... so he put a holley pump on it.. it would stall just idling or driving down the road.. i could hear the fuel pump speed up. just before it stalled.. instead of putting on a fuel filter to protect the pump. he installed a second pump in parallel.. nope.. i could hear one pump speed up. then the second pump speed up and then the engine died as the fuel in the Thermoquad float bowl was used up.

    Kodi nox
    Last edited: Oct 1, 2020
  7. Gerald Morris

    Gerald Morris Senior Member

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    Mar 9, 2016
    I LIKE this use of an electric fuel pump. I used one once on a 1955 Chevy Apache, just because getting the original style mech pump wasn't worth the cost. o more vapor lock, but the pump delivered too much fuel. Wound up trading the truck for a '60 Ranchero w an early 289 in it. THAT was a HOT rod.

    For vapor lock in my fuel lines, I've insulated the last 8 ft. of the line, up to the pump. I still have a little vapor when it gets over 102 F outdoors, but not much. If I wasn't driving Tilly daily, an electric w momentary contact to prime the carb would appeal MUCH. Brilliant!
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