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ecm b fuses blowing?

Discussion in 'The Garage' started by k5floyd, Oct 23, 2004.

  1. k5floyd

    k5floyd 1/2 ton status

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    i have an 88 k5(350 tbi). its mostly stock except for a detroit in the rear, k&n, msd ignition, distributor, and wires. anyway, 2 weeks ago the ecm b fuse blew, and the engine died. i swaped the fuse from the radio into it, went to a friends house close by, put in a new 10a fuse, everything was fine, no big deal. then it happened again last night right before midnight while i was on my way home trying to get in before curfew so my old man wouldnt fuss at me. i put a spare 10a fuse i now had in it and the second it was in it blew. so then i swaped the fuse from the wipers into it, same thing happened. then i tried the fuse from the radio, and still it blew. /forums/images/graemlins/frown.gif why is it doing this? where/what could be causing it to short out? could it be the msd ignition? it did happen 2 or 3weeks after i installed it. or is the ecm possibly be bad? if so why is just the ecm b fuse blowing? /forums/images/graemlins/confused.gif
     
  2. k20

    k20 3/4 ton status

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    ECM B runs the fuel pumps. You may have a fuel pump going out. When the fuse blows the truck dies correct? Have you noticed a reduction in power? I know there is something else on that fuse(i cant remember what it is) but fuel pump would be my guess.
     
  3. COCHEV

    COCHEV 1/2 ton status

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    my neqhew just had this happen in his 94 s-10. been wondering why. the pump is kinda loud, but i thought that was just a chevy thing. LOL! anyways, i'd like some info too /forums/images/graemlins/ears.gif
     
  4. k20

    k20 3/4 ton status

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    Yeh I had the prob when my ecm b blew, My pump had been gettin loud, then the fuse popped and I rolled to the side of the road. Stuck in a diff fuse switch tanks and rolled on. That pump was gettin loud, cause i assume, it was lockin up.
     
  5. dyeager535

    dyeager535 1 ton status Premium Member

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    To get this problem straight:

    Does fuse blow if the ignition is in the off position?

    if yes, I should stop typing now. /forums/images/graemlins/smile.gif

    If the fuse doesn't blow with key off, does it blow if you turn the key to "run" but do not turn it one notch further to start?

    I don't know the TBI wiring setup, so what else on that fuse could be a problem, but if the fuse blows in run, even before you try to start it, it should be very easy to check the fuel pump as culprit. (at least it is on my k5)

    Find the two wire connector near the tank, and disconnect it. Put a new fuse in, and try to replicate what happened. If you've "solved" the problem, then you know something after that connector is the problem. Either the pump wire going into the tank, or the pump itself.
     
  6. COCHEV

    COCHEV 1/2 ton status

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    my newphew's blew going up a pass, pulling a trailer. he replaced the fuse and it seems to be running fine. that was a week ago. /forums/images/graemlins/dunno.gif
     
  7. anthony stark

    anthony stark Registered Member

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    My plastic tub in the fuel tank came loose and broke the sending unit. This caused the ecm b fuse to blow whenever the tub hit it just right. My fuel guage was out also. I believe this has happened again because my fuel guage is out again, I'm going to remove the tub this time.
     
  8. k5floyd

    k5floyd 1/2 ton status

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    i unpluged the connector to the fuel pump, put in a new fuse, turned it to run, and the fuse still blew. this would mean its not the fuel pump, correct? where is the fuel pump relay located, and what does it look like? i think that is a possible problem.
     
  9. dyeager535

    dyeager535 1 ton status Premium Member

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    Probably not the sender then. /forums/images/graemlins/smile.gif

    Fuel pump relay on my setup (TPI) is a fairly flat plastic housing, with 5 or 6 wires running into it. relay pics Go to page 3, it's the picture titled "relays" of all things. There are 4 plastic parts pretty much centered in the picture, two with oval shaped bodies on the right, (just behind the brake line) and the fuel pump relay is the third from the right.

    On mine when I got it, one of the wires running into the relay was missing the insulation right at the connector for th fuel pump relay, and it would have been very possible for that to short to the wire next to it.

    If the wiring there looks good, you can check the wire that goes to the fuel pump (on mine the pink wire is the fuel gauge, but thats not all setups) to make sure it doesn't have continuity to ground. Need a multimeter for this though.

    You should be able to unplug the relay as well and try the key on/engine off test again. You will also have an oil pressure switch in the fuel pump circuit, I'm not sure where that is located on your setup.
     
  10. k5floyd

    k5floyd 1/2 ton status

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    got it fixed! went to oreily auto parts and got a new fuel pump relay, 8.99. put it and a new fuse in and started up. thanks for the help guys. /forums/images/graemlins/woot.gif
     
  11. southernspeed

    southernspeed 1/2 ton status GMOTM Winner

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    See!!! This is the best web site in the world and worth every penny!! It can save you a fortune!! /forums/images/graemlins/waytogo.gif /forums/images/graemlins/waytogo.gif
     

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