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  • IMPCO inadvertantly switching over to gasoline

    I've got a 2012 Silverado with an IMPCO CNG Bi-fuel system, installed by OEM Systems out of Oklahoma. I have been having a little trouble with the CNG side inadvertently switching over to gasoline with plenty of CNG available. It began a couple of weeks ago with just a steady beep/solid red light(the same as when I run out of CNG) being displayed on the gauge. After stopping the vehicle and shutting off the beeping sound, I was able to switch back to CNG. It seemed to work fine. I read the manual and the only thing mentioned is a malfunctioning problem which is indicated by 3 beeps every 20 seconds. At the time that wasn't what was happening. It was acting as though I ran out of CNG until a couple of days ago when after filling my CNG tank the 3 beeps every 20 seconds did occur. I have been advised that it could be a number of issues. Considering I guess the system back in 2012 was rather temperamental and it could be a number of things.. I reset the ECU via disconnecting the battery and made sure I had good gasoline. I guess these systems don't like ethanol. After doing this I ran an entire tank of CNG with no problems until it happened again 2 days ago. I have been told it could also be the Pressure transducer or the temperature sensor. I have attached a couple of pics where it shows what I believe to be the temp sensor(2 wires, light blue and yellow) and what I believe to be the Pressure transducer(3 wires). So has anyone else experienced this problem? Does anyone have a diagram of this factory installed system for 2012? I am probably going to replace the temp sensor first however not sure where to buy one. Any advice would be appreciated. If I did have to replace pressure transducer which I'm not 100% the one attached to regulator is it, Cowboy informed me that there are two different types...1 with an o"ring and another without. I was also told the transducer is located near the tank however I don't see it there so I am assuming it is the one with 3 wires in the pic what appears to be the high pressure side??. Sorry for the lengthy message..trying to explain the problem. Oh yea, I did disconnected the sensor plugs cleaned them and used some dilatric gel. Thought maybe I had a bad connect, didn't fix problem. I also changed the spark plugs and wires. The truck has 117,000 miles

  • #2
    I had the exact same problem back in january with my 2012 ford F250 with an Impco conversion! turned out to be the filter element in the condensate trap! I replaced it and problem disappeared ! When I cut apart the filter it had a tarry black substance coating the inside of the element .Not alot but enough to create a pressure drop across the element I am sure . You can get the filter elements from parker Hannifin. if you need more info on element reply back and I will dig it up. hope that helps!

    Comment


    • cngtennessee
      cngtennessee commented
      Editing a comment
      When you changed the element was the bowl dry? I dropped the bowl and checked it, the bowl and element was dry so I just put it back on. Never thought to change it out....don't know when the last time it was changed.

  • #3
    Warnings in the literature for my 2013 Silverado 2500 IMPCO factory bi-fuel advise NOT to use ethanol gas as it can mess up the CNG system, ECU program, etc.
    I don't know the specifics, but that could be related to the situation you are experiencing.
    Might want to chat with a Chevy dealer authorized CNG tech about your situation. Maybe there is a tech bulletin out on that issue?
    '13 Chev Silverado 2500 Ext Cab Factory Bi-Fuel
    '08 Green Tea Metallic GX
    FMQ-2-36 Fueler

    Comment


    • #4
      I think you will find ethanol (10% or less) in the gasoline is acceptable. It is a requirement for any new vehicle that ethanol up to that percentage can be used. It is common for almost all gasoline to have it added. The caution is not to use higher levels of ethanol, i.e. E-85 as an example. The CNG Silverado is not "flex fuel" capable nor is the Impala. You would be nuts to use E-85 anyway, but that's a whole 'nuther discussion .

      Comment


      • cngtennessee
        cngtennessee commented
        Editing a comment
        Yes the manual states to not go above 10%. Although Ray at Crains Automotive said that I would be surprised to know how much ethanol is really in the gas we buy. I will only be using 100% gasoline from now on.

    • #5
      Is the weather getting cold where you are now? I believe the 2012 IMPCO Silverado system used BRC injectors, which have a real hard time in cold weather. IMPCO came out with a "cold weather retrofit" kit which they provide (provided?) for free to those with affected vehicles. The kit is kind of a complex solution as it routes engine coolant to the injector rail so as to keep the injectors warm. OEM Systems would know more about it.

      Comment


      • cngtennessee
        cngtennessee commented
        Editing a comment
        I will call OEM tomorrow to see if the retrofit has been done. Thanks

      • cngtennessee
        cngtennessee commented
        Editing a comment
        No although we did have one night dip down to middle 40's. Since it's been in the high 70's - low 80's.

    • #6
      I have Prins kit in my '06 f150 5.4. It does the same thing occasionally in cold weather till the engine gets warmed up. Sometimes to the warm saturated point. Just pull over and shut the ignition off and restart. Started doing it 4 or 5 years ago.

      I never run ethanol laced gasoline anymore but then again I've only used about 35 gal gasoline this year and worry about the water separation issue. (23,000 miles so far this year) I seriously try to avoid public fueling also as have had moisture issues with it too.

      Comment


      • cngtennessee
        cngtennessee commented
        Editing a comment
        Thanks Amfuel. I was talking with Steve who is on this site regarding the fact that I might just have to live with it as long as it doesn't get any worst. With that said, we both agreed that we would like to discover the root cause simply because it's designed to perform without any glitch. Considering the fact that it switched over after 100 miles of highway driving(I have a small transport company that this vehicle is part of) it seems to be doing the switch over after it's plenty warm. Believe me,if we can do some simple inexpensive things(change filter element, reset ecu, use 100% gasoline) and it doesn't solve the problem, I will be happy to shut ignition off and restart before throwing sensors at it. Although a nice man by the name of Ray at Crains in Arkansas might have a used working temp sensor he will send my way. Not sure what these thing cost new but I sure would like to give this a go if all I have to do is change it out. If I have to replace any of the sensors he would switch the temp sensor first. We will see.

    • #7
      Forgot to mention - I experienced this happening on my '13 Silverado on two occasions. Went to the dealer service and they informed me there was a tech bulletin issued to watch for this, and if so the CNG ECU was to be replaced with an upgraded version. As this was still under warranty, it did not cost me. It apparently is an issue that only occurs on some units, not all, so they did not issue a blanket recall. You should check with your CNG service authorized Chevy dealer.
      ?Another work around I found they did while awaiting the replacement was to clear the check engine flag caused by this, and it went back to CNG run OK...
      '13 Chev Silverado 2500 Ext Cab Factory Bi-Fuel
      '08 Green Tea Metallic GX
      FMQ-2-36 Fueler

      Comment


      • #8
        Just had my cng fuel rail temperature pressure sensor replaced under warranty in my 2015, I made a post about it.....maybe same problem

        Comment


        • cngtennessee
          cngtennessee commented
          Editing a comment
          Do you know where this sensor is located...pic. Got your vm, will call you today.

      • #9
        this is the part number on my invoice 22991077, description says sensor 3.682.....250 at dealership, 135 here

        http://www.gmpartsdirect.com/chevrol...ressure-sensor

        Comment


        • #10
          When I changed the filter there was no Moisture in trap also external of filter looked ok . But when I cut it open it had that tar like substance coating the inside . I seem to remember seeing somewhere they wanted this filter changed every 10 k miles . I know I am going to do mine annually to avoid that issue in future I had about 30k miles of CNG use when my problem cropped up !

          Comment


          • #11
            http://gm.oemdtc.com/2649/bi-fuel-ga...ierra-2500hd/6

            Thought this was a good read

            Comment


            • #12
              I am perplexed in a good way. Here is a list of what I did....1) Reset ECM 2) Unplugged all sensors, cleaned and used some dielectric gel to keep clean 3) began using 100% gasoline 4) changed filter see pic. I have run approx. 400 miles since making these changes and have had no problems with the system inadvertently switching over to gasoline. Not sure what of the 4 things I did corrected the problem but so far so good. Thanks to all of you for giving me your advice. This site is a blessing.

              Comment


              • #13
                Mine looked Just like that until you cut it open! I bet it was the filter !! Make sure you got a spare!

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