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CNG leaking after filling

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  • CNG leaking after filling

    Sometimes after filling up when I remove the filling nozzle apparatus (is there a name for it?) I can hear CNG leaking. Reattaching the filling nozzle and opening the filling valve with the pump off seems to fix the problem.

    What exactly is happening and is there any corrective action that can be taken?


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

  • #2
    Re: CNG leaking after filling

    Same here, I notice that when i fill up and get a good fill it will leak at the fill nozzle. I believe this is caused by the freezing temps generated at the fill nozzle and any moisture results in ice that causes a leak. I never have this problem when it's warmer. I don't know if a new nozzle would fix this. I'm not sure this is all correct, but from what I can tell it's very probable.
    2000 Escalade (option 3 conversion) FOR SALE
    2004 F150 XLT (OEM conversion)
    2000 Camry (Awesome Car!!)

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    • #3
      Re: CNG leaking after filling

      If you are getting THAT much pressure drop at the nozzle that you are getting ice crystals, it sounds like you might actually have a problem with your receptacle itself. If the check is fully opening, there should be near as much flow area as the hose and piping on either side, and you shouldn't have that much of a spot cooling effect. A failing check valve would be resonsible for both the chilling (from it not opening all the way), and the leaking (from it not closing all the way). Might want to look into what it would cost for a replacement receptacle.
      1997 Factory Crown Victoria w/ extended tanks ~~ Clunkerized!
      2000 Bi-Fuel Expedition --> ~~ Sold ~~ <--

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      • #4
        Re: CNG leaking after filling

        I would also consider the "additional check valve", except early Ford, that should be in the system. I would sound as if the this valve would be a consideration.

        Larrycng

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        • #5
          Re: CNG leaking after filling

          I believe my valve is fine it the cold that's generate and the cold temps here (15-25F). All the piping gets iced over too.

          I don't have a check valve on my setup, I thought that was weird, but I guess they depend on the tank valve for that. I was thinking of adding one, would this keep gas from passing back to the fill nozzle, so if it did leak, only a small amount would be lost?
          2000 Escalade (option 3 conversion) FOR SALE
          2004 F150 XLT (OEM conversion)
          2000 Camry (Awesome Car!!)

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          • #6
            Re: CNG leaking after filling

            I recently had 2 Civic GXs with leaking check valves in cold weather. The first one was leaking at the connection of the recep and nozzle. I went to change the Oring and found icing covering the Oring. Cleared the ice and it was OK again. I realized that the leaking check valve was causing frost at the recep and when the nozzle is connected the icing occurs. Getting some silicone lubricant into the check valve may help the check valve. (with pressure working against you that can be an issue) It may cost you a new recep. Good luck. These GXs are a dealers cars so I only have to report my findings. BTW it was good and cold here in Wi.

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            • #7
              Re: CNG leaking after filling

              I had also trouble to prevent my receptacle from leaking during wintertime. Then one time when I was going to fill up in freezing weather and applied some lipsalve in order to keep my lips from cracking, it occurred to me that maybe the rubber O-ring could use it too. Just a touch of it on the inner side of the O-ring and the leaking was history!

              I guess the O-ring had been dry and leaking all the time during fill-ups, but how can you tell it when the filling itself is so loud? And where there is leak, there is chilling, and even a little moisture can create ice crystals between the valve surfaces. Then when the fill-up stops, a leak supports further chilling and the ice crystals will prevail.

              The good thing here is that once someone has had this problem and starts to lubricate his/her O-ring, some of that lubricant is bound to stay at the filler nozzle too, so this enlightened person will then aid the whole community of fillers. If the filling station crew would be enlightened enough, they would lubricate the filler nozzles periodically, and the leaking would never occur.

              Hope this helps. Besides this issue, I have had nothing but good experiences of CNG driving in cold weather.

              Best Regards, Hewey

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