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CNG Cold Start Issues

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  • CNG Cold Start Issues

    I have a 2011 F150 5.0 L CNG/Gasoline truck with an IMPCO system installed. I bought it at auction from the State of Wyoming and brought it to California 2 years ago.
    I use it once or twice a week for relatively short trips.
    Over time it has become increasing difficult to cold start while running CNG. I have been switching to gasoline when I start it after it has sat for a day or more to get it going. It starts right away on gasoline.
    I push the button to allow it to automatically switch to CNG when it gets to running temperature. It starts fine on CNG after the engine is warmed up.
    It seems that the "choke" or enrichment for CNG cold starts is not working.

    Anybody have experience with this?

    Any advice?

    Thanks in advance!

  • #2
    In 2012 IMPCO offered a free fix for cold weather issues. The package routed engine coolant to the CNG injector fuel rail to keep it warm, but did little to assist with cold starting on CNG. If the truck came from Wyoming then this was probably installed. As I recall, the 5.0 liter F150 system forces the truck to first start on gasoline, and then changes over to CNG once the engine is warmed up. It all boils down to the IMPCO/BRC injectors really have a hard time in the cold... What are your ambient temperatures currently?


    • #3
      When I first brought the truck home it started easily at any time/temp, but after a year or so, it got to the point where if the engine is cold, I have to switch to gasoline to start it up.

      Overnight temps in SoCal seldom (but occasionally) drop below 50 degrees. When it does get colder than 45-50 degrees the truck will start on gasoline automatically, without pressing the on/off dash button.

      When it's not that cold in the mornings (above 50 degrees), if I don't switch CNG off, it is a very hard start with a lot of cranking with the starter, if it starts at all.

      I'm old, so to me it's like trying to start my old f-100 without using the choke.