new engine bucking under load

Discussion in 'Engine/Drivetrain' started by gforcepdx, May 20, 2017.

  1. gforcepdx

    gforcepdx Newbie

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    ive got a 77 long bed 20r. i have 4k on a rebuild with new 32-36 weber. having 2 separate issues.

    1) alternator and oil light are on, with battery not receiving charge. i've replaced the alternator, regulator and battery. still have 2 dash lights and no charge

    2) engine bucking/sputtering under load, with trailer... on grade.

    i have a new engine, new weber, 2 fuel pumps (elect and mech), new fuel filters, new fuel pressure regulator and gauge. i changed my weber adaptor gaskets after finding a manifold leak. i've also replaced the engine-to-frame ground strap.

    after adding the weber i turned my pressure to 2.5 as per factory spec. i actually went through a bad fuel regulator and gauge before replacing both with different brands.

    the first time the engine started bucking, i turned the pressure up to 4 pounds, then 4.5 pounds pressure.

    it was after this i changed the fuel filters.

    the truck has good acceleration without the trailer. not perfect but better generally than the stock carb with 300k on it. it seems to buck wide open, with a heavy trailer, on an incline. this last part makes me think it's a fuel delivery issue.

    i've currently got the fuel pressure gauge under the hood, making it impossible to take pressure reading's "while it's happening". i may add enough fuel line to take readings from the cab. but not yet.

    i haven't looked at the jets yet but the guy that installed the carb said i'm set up for economy.

    also, the muffler blew 2 weeks ago... like a fire cracker. in pictures it resembled a clam shell. so i'm experiencing back pressure issues at the moment.

    i've since closed it up winding a loop of nylon rope with a wrench several times to close that clam shell back to a cylinder. ive tack welded it for now though it still leaks. eventually i'll add a flow master and headers.
     

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