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Home >> Chevrolet >> 2002 >> Blazer 4D Utility, 4WD, Part Time >> Repair and Diagnosis >> External Pages >> Different car >> Section 1168 (Engine Controls - 6.0L - Alternative Fuels (Introduction)) >> Description and Operation >> Fuel System Description >> Fuel Supply Components >> High Pressure Lock-Off (HPL) Solenoid

High Pressure Lock-Off (HPL) Solenoid

WARNING: This page is about a different car, the 2004 GMC Sierra and 2004 Chevrolet Silverado. However, it is still accessible from the selected car via links, so may be relevant.

The HPL is a normally closed, solenoid valve. The HPL solenoid and a low pressure lock-off (LPL) solenoid in the fuel line prevent fuel flow. The powertrain control module (PCM) commands ONLY the HPL open for 1 second at EVERY ignition ON in order to prime the CNG fuel system. The CNG prime pulse charges the fuel line which allows the fuel tank pressure (FTP) sensor to monitor the amount of fuel pressure in the system. The PCM commands BOTH the HPL and the LPL open when engine RPM indicates that the engine is cranking or running on CNG.

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