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Need direction on checking out CNG

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  • Need direction on checking out CNG

    I just brought a 2001 F-150 4X4 from Bay area. It is bi-fuel. In the area I picked it up, CNG wasn't available and all the indications were the CNG was empty. The seller said she had been driving it on CNG earlier, but it had been sitting for several months. Other dealings with seller taught me seller was honest, so I brought truck back to Utah on gas. When I went to fill at Questar, it only took a little over 2 gallons. I noticed about 3800 PSI showing on pump. An employee of gas company there said the reason it only took a few gallons was it was full. Apparently the CNG isn't working right now.

    I have the owners manual on CNG, but can't really figure it out.

    Where do I start? I am fairly well mechnically inclined, so should be able to check things out once I know what and how.

    As information, the switch by the steering column was in the on position for the CNG. I also know the key has to be shut off to switch from gas to CNG and visa versa. The green light on the switch hasn't glowed, that I have seen, even when you first turn the key on and it is supposed to momentarily go green (at least that's what I understand from talking to my son who has an identical truck with extended cab, but not 4WD).

    Any suggestion? There is a company in the Salt Lake area who services these, but I understand a trip into there usually costs hundreds.

    Thanks.

    Max

    P.S. I bought the truck for about half of what identical trucks in this area are going for with CNG, (plus, I still have the $3000 credit). The truck is a good buy, even without the CNG.

  • #2
    Re: Need direction on checking out CNG

    Sounds like a nice truck.....Light should at least flash. May be blown fuse??? or other electrical/electronic issue...would look for fuses first and then recommend having Sno-Motion or a Ford dealer with a technician at least do the initial diagnosis. An accurate diagnosis may be worth the cost and should be detailed enough to decide if the work is doable by yourself.

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    • #3
      Re: UPDATE

      Thanks,
      I may have to do that.

      I checked the coalesent(sp?) filter. It vented gas, but there was no oil inside and the filter barely had a slight staining on the outside. The inside of the filter canister was completely clean. I ran my finger inside it and there was no residue.

      I found two hour meters behind the driver's seat, one for gasoline and one for CNG. The gasoline had 2000 plus hours but the CNG was zero. It may be possible it has never run on CNG.

      Where are the fuses and relays for this? The manual isn't clear at all. It looks like they could be in the flat box next to the intake on top, but I would rather be safe than sorry. As far as breaking down and going to a dealer or service place..some charge over a hundred dollars to change the coalesent filter. My son found the exact filter from the manufacturer for about $5 and once you have changed the filter, it can be done in no more than 15 minutes.

      Thanks in advance.

      Max

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      • #4
        Re: UPDATE

        My truck is a little older(1996 Ranger) so the computer is probably different, but to switch between gas and CNG i have to flip the switch then cycle the ignition on then off 3 times. The switch itself might be bad, use a volt meter to see if you have power to both sides of the switch, middle should be ground with around 12.3 volts running to both sides of switch(depending on what its set on)
        You can do anything except light a paper match, on a marshmellow, underwater!

        R.I.P. Taylor and Chris

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        • #5
          Re: direction for quick check.

          Will try triple switch trick. Thanks

          Where are fuses? The CNG guide with owners manual wasn't clear.

          Max

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          • #6
            Re: Need direction on checking out CNG

            Any ideas on what system is installed on your vehicle? If it is a GFI factory installed unit, verify that the power distrbution panel is powered with the switch selected in cng mode. The panel will have 2 or 3 relays, along with 2 fuses. Check and verify that the system has power. You can also contact me by phone if you need help, Kevin

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            • #7
              Re: Need direction on checking out CNG

              Kevin,
              Thanks. I see you are in Phoenix. One of my sons bought his truck from someone in Phoenix.

              The system is factory GFI. It is model #02001009 serial # 01842506. The label on the door jamb indicates it was installed in August 2001. The label over the radiator shows it was due for inspection sometime in 2004, and next to that I can see where some marked in the foil like label some month in the year 2009. I take if from this it was functioning on CNG at on time.

              I take it the power panel is the little panel near the battery with two fuses and two relays. It also has a red connector with a bunch of white wires which seem to match another connector near the Compuvalve(?).If this is it,I checked the fuses and they both look good, but unfortunately I dropped one of them. I see there was a ground wire cut on the dashboard behind what I think is the Compuvalve (I'm guessing it is the flat box with the silver lid on the pax side of intake?) . The screw is green and has about four connection including the one cut.

              I am not sure how to check the panel for power with the switch on, I am assuming with a volt meter on the fuse slots with the switch by the dash on?

              I appreciate your taking time to help. I work the night shift and have been up for almost 20 hours. I'll check more when I am thinking a little more clearly.

              Max Blair
              Kaysville, Utah.

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              • #8
                Re: Need direction on checking out CNG

                Max;
                Champion Ford on 90th south in SLC has a great CNG mechanic - Dave Fakrell, call and ask for Tom the service manager and he can get you to Dave. We have cycled many CNG Ford trucks and cars through Dave for repairs ( when we can't handle the repair ourselves or warranty work) and have good results.

                Jeff Nooorda
                Kaysville

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                • #9
                  Re: Where is manual shut off, if any, on your trucks?

                  Thanks, for information on Champion Ford also.
                  As information, if anybody's interested, I tried to check out all I could first.
                  Near the battery, there is a power relay module for the CNG system. It has two fuses which were both good. The purpose of the module is to run power to the compuvalve and switch from Gas to CNG. The fuel pump is wired through one of the relays in it's "off" or unpowered position. When the CNG system goes on, the relays switches the power to the CNG system away from the fuel pump. I found that the two hour meters were also wired to the fuel pump output lines from this relay. When power is going to the pump, it was also going to the Gas meter. When it switched to CNG, that power would then goto the CNG gauge. Because the CNG gauge had no time on it, I am guessing it has not worked since the gauge was put on.(The guages have a separate relay to switch power). Because of this, I am guessing the problem is related to the installation of the gauges.
                  I checked the steering column switch, as well as the connections the tank in the bed and found no power at either. Both fittings on the tank have the same resistance reading as the one on my son's working truck. It momentarily hooked power to the tank and heard the valve click, so that isn't the issue.
                  I have made an appointment with Sno-Motion in SLC for Monday. However, when I was talking to Dave there, he said to check for a shut off line around the coalescent filter under the cab. I could not find one.

                  Do any of you have a manual shut off in the line, and if so, where is it located and what does it look like?

                  Thanks,

                  Max

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