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  • how to run without CNG

    What do I need to do to run my 5.4L F150 on gas only while I work on the compuvalve?

  • #2
    Re: how to run without CNG

    Originally posted by troach View Post
    What do I need to do to run my 5.4L F150 on gas only while I work on the compuvalve?
    There is a thread about how to repair the Compuvalve and IIRC it mentions plugging a couple of lines. People are all the time removing failed compuvalves and running on gasoline without issue.


    ?Innovation is driven by having access to things.? -- Gleb Budman, CEO of backblaze.com

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    • #3
      Re: how to run without CNG

      I just ran into a guy that had to do this. Seems like it wasn't a big deal.
      Last edited by blinxpro; 11-30-2009, 03:09 AM.

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      • #4
        Re: how to run without CNG

        "So my mechanic friend said he would help me to rebuild the compuvalve. I figured what have I got to lose. We pulled it off and took it apart today. It was not hard to get off the truck and you only have to plug 2 vaccum lines to get the truck to run on gasoline without the compuvalve on. I used a golf tee on one of the vacuum lines and a lid from a bottle of water for the other. It started fine after putting the "plugs" in."

        I cut and pasted this from a previous post of mine. It is very simple to do. You can find more information about this a couple of pages back in the post titled "rebuilding compuvalves"

        I also posted some pictures on that thread of my in progress compuvalve rebuild.

        I ended up replacing the compuvalve with a working used one. Good luck.

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        • #5
          Re: how to run without CNG

          Thanks for the reply
          I only found the one vacuum lin e but I think they meant the coolant line for heating the gas.

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          • #6
            Re: how to run without CNG

            I’m curious, what kind of problems are you having with your compuvalve?
            Mine is acting up too and I’m wondering at what point to I start looking for a replacement.

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            • #7
              Re: how to run without CNG

              A couple of things started to act up. It would occaisionally not start in the mornings on CNG, I would start on gas and switch a mile down the road. 4 other times I was driving on the interstate and the truck stopped running on CNG. Pulled over and restarted on gas and would drive home. It would run the next day. The final issue was after changing a blower fan, it would start on CNG, run for 10 seconds and then die.

              Thought I would try to follow the procedure that is posted on this site

              It was easier than I thought to take it apart and hopefully it will go back together just as easy and work better.

              I also changed the coalescing filter at the same time

              Tim

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              • #8
                Re: how to run without CNG

                Mine is acting very similar with a check engine light on the CNG side.
                I took it to Lancer Auto to get scanned and they said bad O2 or wire to O2.
                I replaced the O2 and I’m still getting the check engine light so now I need to check the wiring.

                Let me know how the Compuvalve rebuild goes.
                Thanks
                Randy

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                • #9
                  Re: how to run without CNG

                  I've never had an engine light or a code with my reader. I think you need a special reader though. Anyone know if a cheap reader will work or do I need a special Ford reader

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                  • #10
                    Re: how to run without CNG

                    I am getting a check engine light and had to go to Lancer Auto to have it scanned with a Ford scanner. My scanner wouldn't work either. i think i have a bad wire to the o2 or a bad compuvalve.
                    I'm going to check out the wiring and rebuild my compuvalve and see if that fixes it.

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                    • #11
                      Re: how to run without CNG

                      Let me know what happened with the O2 sensor. Is it the one in the air intake after the filter

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                      • #12
                        Re: how to run without CNG

                        I'll let you know.
                        I didn't get a chase to work on the truck this weekend.

                        There are 2 o2 sensors, well 4 but the compuvalve only reads the 2 in front of the cats. The Ford pcm reads the same 2 in front of the cats and 2 more down stream after the cats in the exhaust.
                        I'm getting a code that the o2 sensor is getting a high voltage reading.
                        I changed the sensor and the code is still showing up so now i have to chase the wiring between the compuvalve and the o2

                        How did your compuvalve rebuild go?

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                        • #13
                          Re: how to run without CNG

                          Still working on it, I have the truck running on gas now though. Finding a lot of small isues on this truck. I bought it 4 months ago and it ran well but I am finding out the minor issues I want corrected. Today was the tranny cooler lines are rotted so I pulled them off. Looking at the rear brake lines has me thinking about pulling them off as well.

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                          • #14
                            Re: how to run without CNG

                            Originally posted by randys2000 View Post
                            I'll let you know.
                            I didn't get a chase to work on the truck this weekend.

                            There are 2 o2 sensors, well 4 but the compuvalve only reads the 2 in front of the cats. The Ford pcm reads the same 2 in front of the cats and 2 more down stream after the cats in the exhaust.
                            I'm getting a code that the o2 sensor is getting a high voltage reading.
                            I changed the sensor and the code is still showing up so now i have to chase the wiring between the compuvalve and the o2

                            How did your compuvalve rebuild go?
                            Randy, if thre O2 voltage is varying (thats important) and averaging high then you're running rich but the system is somewhat in control and biased rich. If it a fixed rich rading around 1 volt maybe slightly higher, then are running rich with and no computer control. In the later situation there is a high possibility of CAT damage


                            larrycng

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                            • #15
                              Re: how to run without CNG

                              Thanks Larrycng,
                              any help is greatly appreciated
                              I'll test for that.

                              Would i see a code on the gasoline side if the cat was bad?

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