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2003 GMC 3500 rear fuel tank won't pump

Discussion in 'Truck & Equipment Repair' started by 2009deerejohn, Aug 5, 2014.

  1. 2009deerejohn

    2009deerejohn Junior Member
    Messages: 5

    My father and I got a steal on this truck in early spring and we've slowly picked away at the ***** list and have it mostly squared away except for the rear fuel tank doesn't pump fuel in the front tank(obviously the gas gave don't work right either). We scoured the web looking for info and finally found some good info on testing the secondary fuel tank relay, PCM(or ECM depending on the source) and so on. The PCM fuse is good, the relay clicks only if you use a jumper of the wire that runs from the secondary tank relay to the PCM(which the computer is supposed to do its self as the rear pump only runs when it's called to transfer fuel to the main tank from what I've been told). That leaves us with the fuel pump in the rear tank is junk or the, yikes, PCM gave up to the gray ghost I think, we've haven't found any damaged wire. We ran a hot wire directly to the rear fuel pump and it didn't turn on but since it runs only sometimes when it's told to by the computer I'm not 100% sure it's dead, nor am I 100% sure the PCM is dead. I am 100% sure the local chevy garage won't get a 2nd chance to fix it because they charge $680 to "look" at it and didn't figure anything out. Please help, our '98 had a simpler issue and a lot of people with 2 tank GM 1 tons have had issues that I know about but they all had the money to have the dealer fix it and don't really know what was wrong.
  2. dieselss

    dieselss PlowSite Fanatic
    Messages: 11,395

    Prob not the fix. Bit ck the gnd for that rear pump. I know its on the frame bit I forgot where it gnds. Usually it us the sending unit in the tank. Usually
  3. 2009deerejohn

    2009deerejohn Junior Member
    Messages: 5

    Thank you, lo, in all the stress I forgot to keep it simple:)