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  • Gm/impco

    Where can I get a wiring diagram for the IMPCO system installed on the Chevy K-2500,my quest is this, there must be a way to create a switch to change fuels.

  • #2
    Re: Gm/impco

    I don't recall any of the aftermarket Impco systems having and auto switch over.

    A relay, toggle switch and a pressure switch should do the trick. Use the load side of the relay to take the places of your manual switch. Then hook the control side of the relay through a pressure switch to ground and put a toggle switch on the hot side as a manual overide.

    Hook the gas system side to the normally open side of the relay so that you to have the toggle switch closed (on) and the pressure switch closed above about (150 to 200 psi) to closed the relay and activate the gas mode.

    When the gas pressure goes below the set point (pressure switch opens) and the relay loses power and the relay goes to open and swithes to gasoline (fail-safe). Or, when you open the toggle switch you loose power to the relay and go to gasoline.

    If you want to get fancy, hook a big red light to the normally closed side of the relay so that when it switches to gasoline the light go on. Toggle switch will also control power to the relay so when you shut off the toggle to go to gasoline it will also kill the red light.

    The number terminals on the relay will be determined by the number of circuits you have to switch. If you can't find the relay you need from a good parts house go to radio shack and find what you need, Make sure that it has a 12 volt coil.

    good luck



    • #3
      Re: Gm/impco

      Put the switch inline with the tank valve. When the valve loses power and closes, the vehicle will think it's out of gas and switch over. Closing the switch will restore normal operation and the vehicle will think it has been re-filled.


      • #4
        Re: Gm/impco

        I have a 94 Chevy 1500. The mechanic at Go Natural (formerly Sno-Motion) told me that the CNG sender switch is broken so the computer thinks there is no gas in the tank. The switch is difficult to find, but he said there is a way to bypass the it and trick the computer into thinking that there is gas in the tank so that it will run on CNG. However, after several hours of work (at $90 per hour) he said he could not get it to work and needed a wiring schematic. Apparently IMPCO said they don't have any. So does anyone know where I can get a wiring schematic or know someone who has done this type of bypass before?


        • #5
          Re: Gm/impco

          I was lucky enough to have my tech tell me today that he couldn't do it without the schematic BEFORE he charged me. But I'm having the same trouble. There must be an archived schematic somewhere. We need it. Im having the exact same issue. Anybody ever get this fixed?