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Fuel Pump Relay Frying... 95 Tahoe 5.7

This is a discussion on Fuel Pump Relay Frying... 95 Tahoe 5.7 within the Technical / Maintenance forums, part of the General Discussion category; I've searched but cannot come up with a conclusive answer. My fuel pump relay (5 pin, unlike what the computers ...

  1. #1
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    Fuel Pump Relay Frying... 95 Tahoe 5.7


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    I've searched but cannot come up with
    a conclusive answer.

    My fuel pump relay (5 pin, unlike what the computers at the autoparts stores say(4-pin)
    Continually will overheat and fry,
    actually to the point that the relay
    is near impossible to touch, and one
    of the contacts melts the plastic.

    When I first got the truck, I thought
    it was my fuel pump going out, replaced that
    and the truck would die on occassion
    without warning(relay overheating I can assume now)

    I found the quick easy trick of swapping
    my a/c relay out in a pinch worked well.

    Anyway, what should I be looking for
    I can only assume there is a short somewhere
    that is causing the overheating at the relay...

    I'm mechanically inclined, but unless I know
    what I'm looking for "electrically" electronics
    can be a challenge.

    So if I need more info for you guys to help me
    let me know, I'll get it.

  2. #2
    loose nut behind da wheel JeremyB's Avatar
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    Re: Fuel Pump Relay Frying... 95 Tahoe 5.7

    Are you having any issues with the oil pressure sending unit, the one wire from the sending unit splices into the power wire for the fuel pump. I can't believe you aren't blowing the ecm-b fuse. There were some vehicles that had the in tank fuel pump connector melt, but you replaced the pump. Have you tried using dielectric grease on the contacts for the relay, corrosion may cause some of the problem.

    A 4 post relay will work on that vehicle, the fifth post is for the fuel prime connector and is used only for testing the fuel pump with the truck off

  3. #3
    FFColburn 96 K-1500
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    Re: Fuel Pump Relay Frying... 95 Tahoe 5.7

    It is doing exactly what my 96 K1500 was doing, it is the oil pressure switch, on mine it is an electrical connector and a screw in oil pressure switch on the top back of the motor by the distrubuter. a little over $20 Napa fix.

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    Re: Fuel Pump Relay Frying... 95 Tahoe 5.7

    anychance you have a picture of what I'm looking for..(location)
    I have the manuals... but I want to make sure I'm hunting
    the right rabbit.

  5. #5
    loose nut behind da wheel JeremyB's Avatar
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    Re: Fuel Pump Relay Frying... 95 Tahoe 5.7

    It's just behind and to the drivers side of the distributor. Its also a PITA to get to or even get a good picture of.

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    Re: Fuel Pump Relay Frying... 95 Tahoe 5.7

    I just replaced mine, and it is a PITA to change.... i used a 3" deep 1 1/16 socket with ratchet, and that seemed to help considerably. I still have no power to the fuel pump relay though... I think I will just send it to the Chevy dealer = : ( I will post what it was in case any one else has this same problem.

    ........NO POWER TO FUEL PUMP RELAY......

  7. #7
    loose nut behind da wheel JeremyB's Avatar
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    Re: Fuel Pump Relay Frying... 95 Tahoe 5.7

    The oil pressure sensor does not power the fuel pump relay. The power is supplied through the underhood fuse labelled ecm-b

  8. #8
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    Re: Fuel Pump Relay Frying... 95 Tahoe 5.7

    Ok, perhaps I'm a complete moron(no comments on that please)

    But my "distributor" is flat not of the standard mechanical
    circular style so I look in there, and see a couple fuel
    lines coming in from the back of the engine passing the
    dist, on the driverside.

    If its on the top of the engine, could it be under the "vortec"
    air box.


    Image found here http://www.newcougar.org/gallery/files/9/6/dist.jpg

    Cali-offroader, can you take a picture of the part outside of the
    truck, so I perhaps can hunt that way?
    Last edited by fredly00; 08-25-2007 at 03:22 PM.

  9. #9
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    Re: Fuel Pump Relay Frying... 95 Tahoe 5.7

    When the ignition switch is turned to ON, the VCM activates a relay that runs the fuel pump for 2 seconds, and then turns it off. This is a sufficient time to build up enough fuel pressure for starting the engine. After those 2 seconds, power to the fuel pump is controlled by a switch in the oil pressure sending unit that closes when oil pressure is at or above 15 psi. So once the engine is started, the fuel pump runs continuously as long as oil pressure is greater than 15 psi. This feature has the obvious advantages of 1) saving the engine by turning off fuel flow in case of a loss of oil pressure, and 2) shutting off the fuel flow in case of an accident that stops the engine, or even a rollover (as the oil pump, sucks air up-side-down). Also, in order to prevent vapor-lock, the VCM activates the fuel pump relay and runs the pump for 2 seconds after the ignition switch is turned off.

    Did find this info useful, regarding another persons question about
    where the power comes from.

  10. #10
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    Re: Fuel Pump Relay Frying... 95 Tahoe 5.7

    Ok I can see it now found some pictures of the oil switch online
    I'll try and replace it tomorrow AM... the engine and surrounding metal is too dang hot for me to be climbing all over.

  11. #11
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    Re: Fuel Pump Relay Frying... 95 Tahoe 5.7

    All done, I'll let you know if the stalling occurs..again.

    Only way I got it done was to take the airbox off
    and the driver side plug wires off the dist.
    and a deep socket like was suggested earlier.
    and a short 8 inch ratchet, only enough room in there to get one click on the ratchet.

    And of course the obligatory sitting on the fan cowl
    with one foot on either side of the engine.

    I did notice for reference(in case I'm fixing the wrong thing)
    the 87 prong on the relay is the one that was getting burned out.(HOT) So if this means something else is a miss let me know.
    Last edited by fredly00; 08-26-2007 at 12:58 PM.

  12. #12
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    Re: Fuel Pump Relay Frying... 95 Tahoe 5.7

    I guess I should have updated this years ago.. but the Oil Pressure Switch fixed everything, never had an issue since...
    Oh yeah and its for sale now... ;) in FL.

 

 

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