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Help 2002 Chevy express 3500 12 passinger van Bi Fuel

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  • Help 2002 Chevy express 3500 12 passinger van Bi Fuel

    Vehicle misfires on CNG at highway speeds blows the air filter cap off and it seems to be starving for gas. Replaced the Mass Air flow sensor and now the dealer says I need a new Low pressure regulator GM part 52370363 and a low pressure lock off solenoid GM Part 52370949. Both have been discontinued. Does anyone know were I can get these parts or a place that can rebuild these parts. Dealer will install if I can get parts. Thanks

  • #2
    The low pressure regulator is rebuildable with IMPCO parts. It is similar to the regulator used on the CNG Cavalier up until 2002. There are no parts inside the regulator that cannot be repaired when using the IMPCO kit--which comes with instructions. I believe the low (intermediate) pressure lock off valve is also the same as the Cavalier part---if not exact, the Cavalier valve will work. There are also several rubber hoses that go up from the engine to the to the mass airflow sensor area that crack from the heat and can cause issues. The one thing that really can give trouble is the plastic housing that sits on the throttle body and attaches to the large hose going to the mass airflow sensor. That gets brittle with age and leaks which will cause a lean condition on CNG. That fact that you had one or more backfires is another reason to look at the plastic housing. It is not available but any fab shop could build an exact replacement out of aluminum which would work much better. Pull the doghouse off and take a look. You can probably repair the whole thing for less than $200 in parts, worse case. BTW---with the MAF sensor mounted remotely, any leak in the intake system will cause a lean condition as the excess air coming into the engine via the leak isn't being reported by the MAF. Look for that leak first, if you find one, repair it (tape, flexseal, whatever) and see if it corrects your problem. If everything is tight, you can check the regulator pressures to see if it is working normally. A sniff test for natural gas at the regulator vent is a simple way to check for a bad diaphragm. If your intermediate lock off valve failed, it would not run on CNG at all---its not part of the problem.

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