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Thread: Under Powered Fuel Pump?

  1. #1

    Default Under Powered Fuel Pump?

    Hello, new to the site but been around cars all my life.
    I have an issue that I can not seem to nail down. Own on old C-10 with a 350 with approx 350 horse. The engine and trans combo ran in another truck I own for over two years with no issues. I transplanted it into another truck, tank ended up being full of junk so pulled some garbage into the carb. I removed the tank, had it acid dipped and then coated with Caswells tank coating. I replaced the front fuel line from the fuel pump to the carb and rebuilt the carb. During the rebuild I upped the primary squirts to a 32 from a 28 to address a slight stumble I had on tip in and add a 1" spacer under the carb. Truck started and seem to run good until I hit the road for approx 20 min then acted like it ran out of gas. I looked and the front bowl was almost out of gas. I fig the fuel pump may be going out or under powered. I replaced it with an Airtex "race" pump that was said to run at a max of 6 psi. This seemed to do the trick, fuel was filling both bowls and the truck ran great doing quarter mile type runs up and down the street, until this morning. Truck started right up, drove 20 min and started heading up a hill and it acted like it ran out of gas. I pulled the site to check the bowl and it looked very low and I could not even see fuel. The truck would start for a min then die. I'm stuck! Fuel pump not big enough? Carb issue? I adjusted the bowl initially even across the bowl when you hold it upside down then put it back on the carb, and finalized the adjustment running, through the site on the carb.
    Thanks. BTW, its a 650 Holley double pump.

  2. #2
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    Quote Originally Posted by 65sub View Post
    ...tank ended up being full of junk so pulled some garbage into the carb.
    Isn't there a fuel filter before the carburetor?

    I pulled the site to check the bowl and it looked very low and I could not even see fuel. The truck would start for a min then die.
    If the float is properly adjusted, I'd inspect the needle & seat assembly.
    May God's grace bless you in the Lord Jesus Christ.
    '92 Ford Mustang GT: 385" SBF, Dart SHP 8.2 block, TFS TW 11R 205 heads, 11.8:1 comp, TFS R-Series intake, Dominator MPFI & DIS, 36-1 crank trigger/1x cam sync, 160A 3G alternator, Optima Red battery, A/C, 100HP progressive dry direct-port NOS, Spal dual 12" fans/3-core Frostbite aluminum radiator, Pypes dual 2.5" exhaust/off-road X-pipe/shorty headers, S&W subframe connectors, LenTech Strip Terminator wide-ratio AOD/2800 RPM converter, M4602G aluminum driveshaft, FRPP 3.31 gears, Cobra Trac-Lok differential, Moser 31 spline axles, '04 Cobra 4-disc brakes, '93 Cobra booster & M/C, 5-lug Bullitt wheels & 245/45R17 tires.

  3. #3

    Default

    Needles and seats are both new Holley replacements. And there was a filter but it was so much stuff, it blew through the screen.

  4. #4
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    Quote Originally Posted by 65sub View Post
    Needles and seats are both new Holley replacements.
    Maybe it's a fuel system problem, not a carburetor problem (since the fuel bowls go dry).
    May God's grace bless you in the Lord Jesus Christ.
    '92 Ford Mustang GT: 385" SBF, Dart SHP 8.2 block, TFS TW 11R 205 heads, 11.8:1 comp, TFS R-Series intake, Dominator MPFI & DIS, 36-1 crank trigger/1x cam sync, 160A 3G alternator, Optima Red battery, A/C, 100HP progressive dry direct-port NOS, Spal dual 12" fans/3-core Frostbite aluminum radiator, Pypes dual 2.5" exhaust/off-road X-pipe/shorty headers, S&W subframe connectors, LenTech Strip Terminator wide-ratio AOD/2800 RPM converter, M4602G aluminum driveshaft, FRPP 3.31 gears, Cobra Trac-Lok differential, Moser 31 spline axles, '04 Cobra 4-disc brakes, '93 Cobra booster & M/C, 5-lug Bullitt wheels & 245/45R17 tires.

  5. #5

    Default

    That was my thought, I replaced the fuel pump. Seems like the same problem. Maybe a bigger fuel pump? Something that puts out a strong 7 psi?
    And thanks for your help!!

  6. #6
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    Quote Originally Posted by 65sub View Post
    Maybe a bigger fuel pump? Something that puts out a strong 7 psi?
    It's probably not the fuel pump, since you already upgraded it.
    What about the fuel pump drive mechanism or some plumbing restriction?
    May God's grace bless you in the Lord Jesus Christ.
    '92 Ford Mustang GT: 385" SBF, Dart SHP 8.2 block, TFS TW 11R 205 heads, 11.8:1 comp, TFS R-Series intake, Dominator MPFI & DIS, 36-1 crank trigger/1x cam sync, 160A 3G alternator, Optima Red battery, A/C, 100HP progressive dry direct-port NOS, Spal dual 12" fans/3-core Frostbite aluminum radiator, Pypes dual 2.5" exhaust/off-road X-pipe/shorty headers, S&W subframe connectors, LenTech Strip Terminator wide-ratio AOD/2800 RPM converter, M4602G aluminum driveshaft, FRPP 3.31 gears, Cobra Trac-Lok differential, Moser 31 spline axles, '04 Cobra 4-disc brakes, '93 Cobra booster & M/C, 5-lug Bullitt wheels & 245/45R17 tires.

  7. #7

    Default

    I will check the line. It's the factory metal line, but maybe it's messed up inside or too small. I thought about the drive rod or a cam issue but the engine only has about 50k on it and it didn't have this issue in the other truck. Also I feel like if it was the cam it would happen all the time not just when it warms up.

  8. #8
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    Quote Originally Posted by 65sub View Post
    I will check the line. It's the factory metal line, but maybe it's messed up inside or too small.
    I'd guess something like this too.

    Also I feel like if it was the cam it would happen all the time not just when it warms up.
    I agree.
    May God's grace bless you in the Lord Jesus Christ.
    '92 Ford Mustang GT: 385" SBF, Dart SHP 8.2 block, TFS TW 11R 205 heads, 11.8:1 comp, TFS R-Series intake, Dominator MPFI & DIS, 36-1 crank trigger/1x cam sync, 160A 3G alternator, Optima Red battery, A/C, 100HP progressive dry direct-port NOS, Spal dual 12" fans/3-core Frostbite aluminum radiator, Pypes dual 2.5" exhaust/off-road X-pipe/shorty headers, S&W subframe connectors, LenTech Strip Terminator wide-ratio AOD/2800 RPM converter, M4602G aluminum driveshaft, FRPP 3.31 gears, Cobra Trac-Lok differential, Moser 31 spline axles, '04 Cobra 4-disc brakes, '93 Cobra booster & M/C, 5-lug Bullitt wheels & 245/45R17 tires.

  9. #9

    Default

    Thanks again for your help. I have been swamped so I haven't had time to try anything, but I'll post when I do.

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