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bought old CNG convert...looking for info

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  • bought old CNG convert...looking for info

    Hello, I just purchased an old (1994) GMC pickup that was apparently converted to run 'Dual-Fuel' . It has a CNG tank in the bed and a plaque on the dashboard that proclaims its clean burn ability. It also has a button that reads "push to read fuel level". This was a Michigan Department of Transportation vehicle. Although I don't plan to run it on CNG because of the lack of availability in my area, I would like to find out as much as I can about the conversion. There seems to be an excessive amount of spark knock running on regular gasoline. There is a part under the hood labeled EDO and another with ANGI. There is a module on the firewall called "GM timing optimizer" but google searches turn up precious little. Can anyone help Identify?

  • #2
    Re: bought old CNG convert...looking for info

    Welcome aboard jdehaan

    Angi is the conversion kit used to run on CNG, I believe that company is still in business. Check the ignition timing and make sure that it is set to factory specification (if the engine still has a distributor).

    The timing optimizer box is probably a "dual curve" unit. It increased the timing curve when the vehicle was operating on CNG. You may have to remove the box. I'll see if I have the documentation on the item. The dual curve information is on the web, otherwise call MSD ignition. I think they're in El Paseo, Tx; ask if someone is still around that knows about it - they made it. It was also call Autotronics

    As for the the CNG tank, have it inspected before you put any gas in the tank (if you decide to). There was a safety recall on some EDO tanks and EDO went belly up. There are still a few in service, but not many. I would advise getting rid of tank, besides if you look on the tank you will see a "do not use after date" and it probably getting close to that date. If there is not a "do not use after date" look for the manufacture date and add 15 years to it, that will be the do not use after date.

    Hope this helps



    • #3
      Re: bought old CNG convert...looking for info


      If it is an ANGI regulator (a big black round device with lots of lines and hoses running in and out) I'd get rid of it and start over.

      Same for the EDO cylinders.

      IMPCO has similar regulators and the cylinders are most likely out of date and should be replaced regardless. There are several companies now that manufacturer CNG cylinders.

      Good luck,


      p.s. you can believe most of what larrycng tells you and some of what I do.


      • #4
        Re: bought old CNG convert...looking for info

        The last time afvman made a mistake, he thought he was wrong and it turned out he was right --sad state of affairs



        • #5
          Re: bought old CNG convert...looking for info

          try useing hitest gas if it has high compression you will get better gas milage than turning the timeing back it should more than pay for the high test with the gas milage and will run better to