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Thread: Do fuel pumps gradually fail?

  1. #1

    Default Do fuel pumps gradually fail?

    While driving around today, I progressively lost power to an eventual stall. At first, only WOT would be affected. Then light acceleration, cruise, then finally idle. After a short engine off period, it would be OK. Acceleration was still rough, and I couldn't go above 60 mph, but it would run for a few minutes, then get worse again.

    After connecting the computer, all I could see was the fuel pressure was gradually decreasing. Everything else seemed okay. Fuel pressure is set at 43 with the pump on, engine off, vacuum hose connected. Normally, the fuel pressure is 34 with the engine on. Logs show at idle, the pressure is 34, but while cruising gradually drops to 20, then to 10. The motor starts missing, losing power, etc.

    I have the Holley 12-920 in-line external fuel pump.
    I changed the pre-filter on the side of the road, thinking maybe I got some bad gas, and it was clogged. No improvement. (100 micron pre, 10 micron post.) Next I tried to fill up the tank with fresh gas (colder, diluted bad gas). This seemed to help a bit, but I still couldn't drive above 40 for any length of time. I could drive around town stop light to stop light, max 40 mph, without problem.

    My pump is not hot. After it stalled, I immediately got out and touched the pump - it was cool.

    The only two things I can think of are that either the pump is going bad, or the voltage to the pump is for some reason gradually decreasing (relay going out???) I need to monitor my at-pump voltage.

    However, my question is: do/can fuel pumps gradually fail, or do they go suddenly/catastrophically?

    If I go hot wire the pump's relay to run, does it put much of a strain on the pump? Would this be a valid test of the pump or the voltage to the pump relay? I'm using the Terminator to trigger the relay that feeds the pump.

    Any other thoughts?
    Last edited by Texasdoc; 11-07-2015 at 09:08 PM. Reason: Edit typo

  2. #2
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    Default

    Quote Originally Posted by Texasdoc View Post
    I changed the pre-filter on the side of the road, thinking maybe I got some bad gas, and it was clogged.
    It seems the clogged pre-filter cavitated the fuel pump and damaged it.

    However, my question is: do/can fuel pumps gradually fail, or do they go suddenly/catastrophically?
    Yes.

    If I go hot wire the pump's relay to run, does it put much of a strain on the pump?
    No.
    May God's grace bless you in the Lord Jesus Christ.

    '78 BRONCO: 508" stroker, TFS heads, 11:1 comp ratio, Dominator MPFI & DIS, cold air induction, Spal dual 12" fans/aluminum radiator, dual 3" exhaust/Magnaflow mufflers, Moroso vacuum pump, Accusump, engine oil & trans fluid coolers, 100HP progressive dry direct-port NOS, A/C, LenTech Strip Terminator wide-ratio AOD/2500 RPM converter, 3:1 Atlas II, modified Dana 44/60-lockers-4.10s, hydroboost/4-disc brakes, ram-assist/heim joint steering, Cage long radius arms, traction bars, 4" Skyjacker lift, 35" mud tires

  3. #3

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    Quote Originally Posted by Danny Cabral View Post
    It seems the clogged pre-filter cavitated the fuel pump and damaged it.
    Is this rebuildable? Or is it time for a new one?

  4. #4
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    Quote Originally Posted by Texasdoc View Post
    Is this rebuildable? Or is it time for a new one?
    Probably not, but contact Holley Tech Service (LINK).
    May God's grace bless you in the Lord Jesus Christ.

    '78 BRONCO: 508" stroker, TFS heads, 11:1 comp ratio, Dominator MPFI & DIS, cold air induction, Spal dual 12" fans/aluminum radiator, dual 3" exhaust/Magnaflow mufflers, Moroso vacuum pump, Accusump, engine oil & trans fluid coolers, 100HP progressive dry direct-port NOS, A/C, LenTech Strip Terminator wide-ratio AOD/2500 RPM converter, 3:1 Atlas II, modified Dana 44/60-lockers-4.10s, hydroboost/4-disc brakes, ram-assist/heim joint steering, Cage long radius arms, traction bars, 4" Skyjacker lift, 35" mud tires

  5. #5

    Default

    Is there any reason I can't use one of those clear glass Mr. Gasket filters as a pre-filter? I know I can't use it as a post-filter, since it likely won't handle the pressure of the EFI. But it sure would be nice to have a way to visually check to see if the pre-filter needs changing.
    Mr Gasket Filter

  6. #6
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    Quote Originally Posted by Texasdoc View Post
    Is there any reason I can't use one of those clear glass Mr. Gasket filters as a pre-filter?
    No, it doesn't support the volume or pressure an EFI fuel pump flows/circulates.

    I have the Holley 12-960 in-line external fuel pump.
    Holley 12-960 is a dual in-tank fuel pump assembly with sock pre-filters.
    May God's grace bless you in the Lord Jesus Christ.

    '78 BRONCO: 508" stroker, TFS heads, 11:1 comp ratio, Dominator MPFI & DIS, cold air induction, Spal dual 12" fans/aluminum radiator, dual 3" exhaust/Magnaflow mufflers, Moroso vacuum pump, Accusump, engine oil & trans fluid coolers, 100HP progressive dry direct-port NOS, A/C, LenTech Strip Terminator wide-ratio AOD/2500 RPM converter, 3:1 Atlas II, modified Dana 44/60-lockers-4.10s, hydroboost/4-disc brakes, ram-assist/heim joint steering, Cage long radius arms, traction bars, 4" Skyjacker lift, 35" mud tires

  7. #7

    Default

    Sorry, typo. I have the Holley 12-920. Original post corrected. OK, I'll order the 162-551 pre-filter (100 micron).
    Last edited by Texasdoc; 11-07-2015 at 09:19 PM.

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