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  1. #1

    Default New pump, ignition switch, and relay..? What next?

    Well, I have a 1988 K1500 with the 5.7 and one day that truck sputtered and stalled randomly on the road. Pulled over and she fired back up again only to stall again a few seconds later. Got it towed home and discovered no fuel coming from the pump. Checked the relay and it was fine so I decided to replace the pump and still no fuel. I should also clarify that I know there is no fuel coming out because I still have the tank dropped and is all dissconnected to verify the filter and other parts are not the problem. These models often have very faulty ignition switches so I went ahead and replaced that and STILL nothing...The pump has power and ground so what else it could be is beyond my auto experience. If anyone has any suggestions it would be greatly appreciatted! Thankfully, I get huge price breaks on car parts so this hasnt cost me more then $60 so far, but is very annoying! Thanks in advance for any help!

  2. #2


    With the tank dropped, you must have plugged the wiring connectors together to power the pump.

    Do you have a meter, you need to check the connector to see if there is 12v on the pump lead.

    With tank dropped, do you have a ground connection?

    If you do not have 12v at the pump, the relay may be bad.

    '09 Avalanche LTZ - Black
    '05 Envoy XL (sold)

  3. #3


    I've found about 2% of aftermarket fuel pumps are bad out of the box. You may discover you've been blessed with 1:50. That being said, yeah, check the electricity going to the leads, as RayVoy suggested. If you're not getting it, swap the relays in your box (most boxes have 2-3 relays of the same type as you're using for the fuel pump... for example, your Horn relay, may be the same type. Swap it with a known good.

    Also, are you getting the "humming" sound hte fuel pump is actually working? If your pump is turning on, and the fuel still isn't getting to your system, you've got a blocked line (likely at a filter).

    2006 Vortec Max 1500
    -Custom Tune (389HP 440 Ft/lbs Trq - Dyno'd) | Volant CAI | Magnaflow Dual-in/out Exhaust w/3" stainless pipe tips | Fully Built Transmission w/ Red Eagle Clutches & Kolene Steels w/ Corvette Servos and Stage2 Shift Kit | 35K Tranny Cooler | Mobil 1 | Royal Purple Rear Diff
    -Spray-in Bed Liner
    -Premium Sound w/lifetime Satellite Radio | Leather | Sunroof | Heated Seats
    -Limbstriping from USING the truck (those are badges of honor)

  4. #4


    wish I could help . i'm having a similar problem w/98 Tahoe. it would not start after filling the tank,so I replaced the pump and relay. still nothing.i ran a jumper wire to the relay and the pump came on .still looking for the problem .

  5. #5
    Sr. Apprentice
    Join Date
    Jun 2013
    1391 N Jefferson St., Anaheim CA 92807


    hi AWick20,
    you have no need to replace anything,firstly do proper diagnos, check power is given to fuel pump, and also y
    ou need to see if the fuel pump relay is turning on. Check for voltage across the relay coil wires colored yellow and light green & blue wires at the relay. There should be 12 volts on them when the pump is supposed to be on. if your problem not found so go to mechanic without wasting time .

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