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2014 GMC Sierra cold weather moisture issue?

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  • 2014 GMC Sierra cold weather moisture issue?

    I had both high and low pressure filters replaced couple months ago, used filters looked very clean after 100k miles. Recently my truck switches out of cng over to gasoline when night temps get down into 20s after 40 miles of 65mph driving. Tank is full. Have quantum conversion kit, has worked fine for two years. I suspect there is likely some water in the cng fuel system that freezes when temp drops causing cng pressure to drop which eventually causes computer to switch back to gasoline. Does this sound about right? Is there a nat gas glycol additive that can be poured into home fueling (FMQ2) hose before filling to clear system moisture or does professional service need to address the entire cng fuel system? Truck operates fine during days when temps in upper 30s, 40s. My previous Honda Civic service specialist said tank must be removed and chemically treated for concerns of moisture in tank. Ok, but how do you service the entire cng fuel system?

  • #2
    It might be that you are not getting good hot coolant flow to your regulator or fuel rail. This hot coolant is not just for cold weather but for Newtonian (Ideal gas) cooling when the pressure drops across the regulator ( [(P1xV1/T1 = (P2xV2)/T2] using absolute pressure and temperature}. Regarding your tank, only way I know of getting moisture out is take the tank out, remove valve and drain it. The filters should show some sign of moisture if you had anything significant in them. I've typically got more compressor oil in my filters than water.
    Last edited by joe_kan; 03-06-2021, 10:33 AM.

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    • #3
      It may have to do more with the natural gas supply. It is not unusual in the winter to get wet gas. If you do not have a dryer before your Fuel Maker it will be passed into you fuel system. Water moisture will not build up in the tank but will cause problems while the gas is in the fuel system.

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      • #4
        My coolant lines to regulator seem to be nice and warm so I assume the regulator is being warmed properly. I wrapped some pieces of moving blanket around the regulator in attempt to reduce heat loss during cold weather. Packing, moving blankets have incredible thermal qualities. If this doesn't help, I'll wrap a low voltage car warming blanket around regulator and run power line to cigarette lighter plugin. I have dryer cartridge for gas supply before FMQ and keep it warm with low voltage 3v heat tape, then wrapped with UHaul blanket scraps, this keeps the outdoor cartridge from freezing during fueling. Dryer cartridges do show some moisture when changing them. Pipeline operators use Ethylene glycol (most effective) or methanol to eliminate hydrates that cause freezing. I may try adding small amounts of Ethylene glycol to tank filler tube before latching the fill quick connect to the tank. I have not seen any discussion about this as a possible solution for cng system water moisture issues. My research suggests the bottom line is if you keep the nat gas and system warm you eliminate hydrate issues. My question remains, relative to ridding a vehicle nat gas fuel system of water moisture, short of complete removal of tank and/or system to remove moisture.

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        • #5
          Over the years, I had three vehicles with cold weather issues; 94 Dodge Van dedicated CNG, 2000 Chevy Cavalier bi-fuel, and 2010 Ford F150 bi-fuel . I've also had a half dozen Honda GXs and a few other natural gas vehicles. The GXs never gave me cold weather problems and I fueled them from the same sources. The cold weather issues on the 2010 Ford F150 went away with a fuel rail update on the IMPCO system.

          My bottom line is, I believe it is more of a design issue with these vehicles as opposed to a big moisture problem. When I removed the CNG system from a 2002 Cavalier bi-fuel, l ran the tank empty, depressurized, removed valve and not one drop of water came out of that tank. The design issues that I've experienced seem to center around the high pressure regulator and the fuel rail. The fuel rail issue was resolved with an update but the other issues never got resolved so I did not use those vehicles on CNG when temperatures were low 20s or below. I suspect the GFI regulator design used in these vehicles does not work well in the cold and I'm not sure whether there is some moisture crystallization associated with that or not.

          My experience owning, operating, and maintaining NGVs for over 20 years.

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          • #6
            Thanks Joe. Great experienced perspective.

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            • #7
              Going to replace Blackstone regulator. My tech says it can behave this way as it begins to fail.

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              • #8
                Not familiar with the Blackstone regulator. The Honda GX regulator seems to hold up pretty well and I have not had any issues with the regulator in the f150 (IMPCO Sequent Plug and Drive) but I've had several GFI regulators that needed replaced on prior GM vehicles (Cavalier, Van). The GFI regulators are probably the lowest cost regulators to replace but the labor to replace is the same. Just checked them out (Blackstone) on the internet, they look similar to the GFI regulators. Good luck to ya.

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