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Home >> GMC >> 1991 >> Value Van 7.4 N >> Repair and Diagnosis >> External Pages >> Different car >> Section 75 (Engine Controls - Remove/Install/Overhaul - 3.3L CNG) >> Fuel System >> Fuel System Purging >> Fuel Cylinder Purging

Fuel Cylinder Purging

WARNING: This page is about a different car, the 1995 Plymouth Voyager and 1995 Dodge Caravan. However, it is still accessible from the selected car via links, so may be relevant.
  1. Open manual shutoff valve. See Figure . Open fuel control valves (counterclockwise) only on fuel cylinders to be serviced. Close all control valves (clockwise) on fuel cylinders not being serviced.
  2. Start engine and operate until it runs out of fuel. Attempt 3 more engine starts. All fuel tubes and opened cylinders are now purged of natural gas between fuel cylinders and engine; fuel system may be opened for repair.
  3. If engine will not start, move vehicle outdoors. Loosen fuel tube at cylinder to be serviced. Wait until all pressure has been released. Fuel cylinder may now be removed.
CAUTION: Although fuel tubes and opened fuel cylinders are now purged of gas, some fuel cylinders (with valves still closed) are still under high-pressure. DO NOT open closed valves until all high-pressure components have been resealed.
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