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    My CNG wont start. Help

  • #2
    need more details, what are you driving/where


    • #3
      From his profile he drives a 2002 dodge ram van 3500 and lives near Kanas City. Given that temperatures are regularly above freezing now its probably not an issue of cold weather causing ice formation in the fuel. I recommend he call Jim at Alternative Fuel Systems of St. Louis to see if he can help diagnose what is going on with this old van.


      • #4
        2002 dodge van 3500 just had plugs, ignition sensor, dist cap, and coil replaced. Just wont get fire. I have heard that the CNG needs a different kind of spark plug.


        • #5
          check the fuel rail pressure sender if it is bad it will cause all kind of problems with starting. you can take the air cleaner off and dump a table spoon of gasoline down it and see if it hits if so you know it is the fuel system and not something else I think it has a filter in the back of the hp regulator in the fiting that the high pressure line from the tanks hooks too. I think the hp reulator is mounted midships on the frame rail on the right side warning 3600 psi should be a main shut of valve near regulator. you can also unplug the fuel rail sender and try starting the computer has a default setting for when it cant see the fuel rail. also if you take the fuel rail sender out (only 150 psi here) and turn the key to on not start it should blow gas for 3 to 8 seconds to prime ( NOTE NO SMOKING WHEN DONG THIS) take dist cap of and turn over and make sure the rotor is turning could be a timing chain or broken pin in bottom of the dist. I think the computer controls the spark so check all wire plugs clean and grease
          Last edited by cowboy; 03-07-2019, 03:21 PM.


          • #6
            Need to systematically work this. I had a 1994 Ram van (dedicated) that had cold weather issues when very cold (below 20 F) that was mostly solved with a CNG filter change. Weather has been a little warmer here lately in the KC area so I suspect that is not your problem as John suggested.. As cowboy suggested, check if you are getting CNG fuel pressure; is the gauge showing there is fuel and put a scan tool on it to determine the after regulator fuel pressure. Also, check the fault codes and see if that gives you any insight.

            If you just replaced the distributor cap and coil check to make sure you are getting a spark. Use a timing light or pull the plug out and place against frame/engine to see if it is firing when cranking the engine. If you removed the distributor to change the coil, check to make sure it was aligned properly when re-installed. Check electrical connections as well - does not sound like you have coil over plugs so check ignition coil, distributor, and ignition wires.

            As Alaska GX.stated please provide as much detail as possible. We are not there and to be quite honest dozens of things may be responsible for a vehicle not starting and we have less information than you do about the problem. If you are working this problem yourself I would recommend getting the factory service manuals and alternate fuel supplement if one exists as well as invest in a couple tools like a Bluetooth OBD2 android/iphone scan tool dongle (~ $20).

            Or ... if you got the money, have a professional look at it.