HELP! Chevy Tech's. Not Camaro.

Discussion in 'Troubleshooting & Diagnosis' started by Bikefixr, Nov 21, 2019.

  1. Bikefixr

    Bikefixr Veteran Member Lifetime Gold Member

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    We've all heard that no good deed goes unpunished. So here I am. Subject is a no-start 96 Chevy van w/5.7L auto. Doing a favor for someone on this vehicle. I was looking for a trigger wire for a relay and managed to short a heavy white (untraced) wire under the column that had an old, uncovered male spade sticking out. Looks to be a 10-12ga. It blew the 40A ignition fuse in the under-hood box and a 20A interior fuse inside the vehicle. At this point I had NO crank, NO dash, NO start. I replaced the fuses and got back Dash and Crank. But I am stuck with a no-start. I have fuel pump and pressure (this is what started the whole mess). I have 5v reference across all sensors. I have power to coil. I replaced the original coil just to be safe, no start. I have an odd thing, however. When my scan tool ( a good one, updated) is plugged in, I get a "no communication" notice. If I jump the fuel pump so it runs, I get communication and no codes. I know there is a known situation where a failed oil sensor can cause a key-off continuous run of the fuel pump. The sensor was replaced previously, but fuel pump continued to run. I pulled the fuse and put a keyed relay across the fuse box terminal and that turned the fuel pump off and got it working with the key. My last thought is a toasted Ignition module near the coil. Replacing that today. If I can't fix it, I bought it. I have 4+ hours and $80 into it. I really should never have touched a truck that had been so hacked up. Tried to do a good thing for someone who couldn't afford a proper repair of the always-on fuel pump, so I did a work-around to keep her going and ended up with this.





    Truck ran well using a switch to turn fuel pump on/off.

    -Shorted a heavy 10-12 white wire under column

    -Lost Dash, Crank, Run

    -Checked all fuses (3x). Replaced 2. 40A underhood IGN and 20A interior box Dash fuse

    -Got Dash and Crank back

    -Have Fuel

    -Have 12V at all fuses and 5V to all sensors.

    -Still have no Run



    What else is on that White wire that is also involved in the IGN circuit? If you could also respond to my e-mail? Bikefixr@aol.com
     
  2. Twisted_Metal

    Twisted_Metal Administrator Staff Member Lifetime Gold Member

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    Do you have spark at the plugs when cranking?
    Possibly a crank shaft sensor gone bad? (I believe that will prevent ignition from firing.)
     
  3. Vettenick

    Vettenick Vettenick

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    Just trying to collect my thoughts. When you say jumped the fuel pump. what do you mean? Did you bypass the relay? With everything being connected, when you turn the key to the "On" position, do you hear the fuel pump run for a couple of seconds? If not, you might have a bad relay that's shorting the fuel pump prime signal wire, making the computer lose communication. I would start there. I can try to get my hands on a wiring diagram, but that might take a day or two.
     
  4. Cardinal

    Cardinal Veteran Member Lifetime Gold Member

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    PM'd you with our youngest son's cell number. He's a certified ASE GM tech.
     
  5. cadillac_al

    cadillac_al Veteran Member

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    Sounds like the ECM may be fried. If you can't get codes out of it I don't see how it can run the vehicle.
     

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