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Testing LPG as emergency fuel

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  • Testing LPG as emergency fuel

    Testing LPG as emergency fuel on a fuel injected CNG vehicle. I have herd a couple of stories about using LPG Vapor, properly isolated from the CNG system and regulated in pressure to about fuel rail pressure on both a GX and an old CNG Caravan. Has anyone on the forum actually done it ? How well did it work ?

  • #2
    I have done it on a 1997 dodge van and on 1998 crown vic. On the dodge van if you drove at higher speeds the propane bottle would frost up and it sounded like a hail storm was going threw the fuel system at slower speeds (30 mph or so) it worked fine. On the crown vic we would run the CNG out and then hook the propane tank to the fill port with the tank upside down feeding in liquid until the pressure equalized then disconnect it. The crown vic would then run about 15 miles. Either way your not stuck.


    • #3
      Not long after I bought my '99 Civic GX, I hooked up a propane backup just in case. I ran a hose from the fuel rail through the firewall to a barbecue tank on the front passenger floorboard. I have left the hose there permanently just in case I need it. The car runs okay, but is lacking a little power and pings under heavier load going uphill. The 12.5:1 compression ratio of the GX engine is a little too high for the lower octane LPG. Natural gas is about 130 octane and LPG is only about 110 octane. Might could retard the ignition timing a couple of degrees to compensate. Because it is drawing vapor from the barbecue tank, it'll only go about 30 miles or so before the tank frosts up and the pressure drops too much. Fuel rail pressure varies between 30 and 40 psi on CNG. I set my propane regulator to run about 15 psi at the fuel rail on LPG. 30 miles isn't very far, but it's better than nothing in a pinch.
      Attached Files


      • #4

        range extending blanket for your range extending propane bottle