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  1. #1

    Default Suburban--Another Fuel Pump?

    I have a 1996 K2500,5.7,136,000 miles, automatic. It had been running great, but quit on the way home a couple nights ago, just like turning off the key. I have spark but no fuel. I can't hear the pump come on when I turn the key. When I put a jumper wire from the 87 to 30 terminals on the relay, I get 11+ volts at the connector where it plugs into the pump harness, but nothing from the pump. I just replaced the pump less than 2 years ago, but it sure seems to be the pump; although I had a lot of symptoms before the last one failed. Any thoughts? One thing that sort of puzzled me: I plugged the relay in but left it sticking up enough to touch the 30 and 87 prongs on the relay with my meter probe. I had 11+ on the 87 but 0 on the 30, with the key on, like it wasn't getting power through the relay. Could a bad relay be the problem? Thanks.

  2. #2
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    Just to be sure before you pull the pump, I would unplug the relay & bridge the wires & check for power at the pump.
    A better test is: If you have a long wire you could also just input power & a good ground at the pump connection itself. This would bypass & eliminate all possible wiring problems & be more definitive.
    1988 Chevy C-3500 2wd (no pic)
    350 c.i. 5.7 L Stock Block, 4 Bolt Mains
    L-31 Vortec Heads, Edelbrock Cam & Intake,
    Holley 650, Flowtech Headers, Magnaflow exh.
    Jet Trans 700R4, B&M Ratchet, 4:10 gears,
    3" susp. lift kit "shadetree"
    No rev limiter, No speed limiter lol


  3. #3

    Default

    That's a good idea; I'll give it a try. I'd really like to avoid laying in the snow dropping that tank, which of course has 30 gallons of gas in it.

  4. #4
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    You don't want to drop it with 30 gallons of gas in it David. Even with floor jacks & 2 guys helping you, it would still be dangerous cuz that's going to weigh 180 lbs for the fuel & another 30+ lbs for the tank, plus they are just plain awkward to handle with the fuel sloshing around & changing the balance... Just to be safe, borrow some gas cans & siphon it out if it comes down to replacing the pump.
    1988 Chevy C-3500 2wd (no pic)
    350 c.i. 5.7 L Stock Block, 4 Bolt Mains
    L-31 Vortec Heads, Edelbrock Cam & Intake,
    Holley 650, Flowtech Headers, Magnaflow exh.
    Jet Trans 700R4, B&M Ratchet, 4:10 gears,
    3" susp. lift kit "shadetree"
    No rev limiter, No speed limiter lol


  5. #5

    Default

    Yeah, I know. I was just referring to the hassle of draining all the gas. Last time, I filled my tractor and two cars and still had to put some in cans.

  6. #6

    Default

    I put a new fuel pump relay in today and changed the fuel filter and now the pump runs when I turn the key on. I have fuel at the test port (no gauges to test with). When I pour a little gas in the throttle body it will run until that's gone, then quits. Not sure where to go from here. Any ideas?

  7. #7
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    Get a helper to start it while you watch the injectors in the TBI. Watch & see if they spray when it's running. If no spray, then pressure could be too low & you will need to put a pressure guage on it. (you can borrow pressure guages at auto parts stores if you leave a $$ deposit.) If no spray, it could also be triggering problem, but I'm leaning towards fuel delivery since your relay got the pump running.

    **You also need to check & see if the pump is continuing to run when you release the key from the crank position to the run position.
    Last edited by stephan; 02-04-2011 at 08:07 PM.
    1988 Chevy C-3500 2wd (no pic)
    350 c.i. 5.7 L Stock Block, 4 Bolt Mains
    L-31 Vortec Heads, Edelbrock Cam & Intake,
    Holley 650, Flowtech Headers, Magnaflow exh.
    Jet Trans 700R4, B&M Ratchet, 4:10 gears,
    3" susp. lift kit "shadetree"
    No rev limiter, No speed limiter lol


  8. #8

    Default

    Well, it won't run unless I'm pouring fuel into the TBI, but while cranking I can't see any fuel spraying in. Can the pressure be tested while cranking, or does it have to be running? The new relay causing the pump to run without resulting in the motor starting suggests what?

  9. #9

    Default

    Well , I got a pressure gauge today and when I turn the key on I have 45 pounds. When I start cranking it actually goes down to around 40. The manual says 60-66, so I guess my pump is toast. Now comes the fun part. Thanks for all the replies!
    Last edited by david78; 01-24-2011 at 10:52 AM.

  10. #10

    Default

    It was the pump. I replaced it yesterday and it started right up and is running fine. I got a Delphi for $157 shipped from Amazon. If you need a pump, that's probably the best deal you'll find on an OE pump.

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