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  1. #1

    Default New guy with a fuel problem (I think)

    Hey guys, thanks for the opportunity to join the board. Hopefully i will get and give some good info. So here's my dilemma

    99 Suburban 2500 with a 454 bogs down bad while under load while giving it some throttle. It has a strong air sucking sound while it does this. I hooked up a fuel pressure gauge and here are the readings.


    Truck cold: ignition on truck not running 50psi and drops down to 22 in 5 minutes
    Truck cold: Running at 47psi
    Truck cold: 2000 rpms at 47psi
    Truck hot: 47psi

    No matter what rpm when hot or cold, it stays at 47psi. So i'm thinking its either the fuel pump or the pressure regulator. What do you guys think?

  2. #2

    Default

    Assuming the pressure gauge is accurate, it seems pretty certain that the fuel pressure is too low. As you suggest, the next step is to determine if the pump is weak or if the regulator is opening too soon. When I've diagnosed this, I used a C-clamp (or similar) to carefully clamp off the return line from the regulator back to the tank. If this causes the pressure to jump up, then the regulator is likely opening too soon. If this has no effect on the pressure, then the pump is likely too weak (or there is something else like a clogged filter preventing the system from generating sufficient pressure.
    '98 K1500 Suburban LS 5.7 L 4L60E NV246 ARB
    '92 Ford Explorer XLT 4x4 4.0 L A4LD BW13-54 Trac-loc rear
    "My toys were the greasy cogs and springs and pistons that lay around all over the place, and these, I can promise you, were far more fun to play with than most of the plastic rubbish children are given nowadays." Danny in Roald Dahl's Danny The Champion of the World

  3. #3

    Default

    Have you replaced the fuel filter? Clogged fuel filter can cause runnability issues.

    In addition to above, pull the vacuum line off the fpr. If fuel comes out of the vacuum line connection at the fpr, it is bad. The fpr diaphragm has ruptured.

    Lastly, fuel pump is getting weak.
    2011 Chevy Silverado LT 4WD 30k miles
    2001 Suburban 2WD, 5.3, V8 185k miles
    1993 964
    1996 318TI

  4. #4

    Default

    Fuel filter is 6 months old. I'll try and check the vacuum line, but getting to the actual unit without taking off the intake will be a challenge.

  5. #5

    Default

    New twist to the problem. I just discovered a puddle of rusty water under the truck coming from the water pump. I looked in the radiator to discover that it is quite low on fluid. So the next question is would low coolant cause the bogging? I was doing some reading on the coolant sensor and the entire engine performance is based on what that little sensor tells it.

  6. #6
    Jr. Mechanic
    Join Date
    Mar 2013
    Location
    adirondacks,n.y.
    Posts
    113

    Default

    I would say youre pressure is low from pump,a good pump will build pressure slowly wwith clogged filter,and not drop that far down in that time span,regulators usually go on the high side.c.t.s needs acurate temp. reading.fill up coolant and see,can anyone say how long that the pump will continue same pressure,hard to say,Id do coolant leak first

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