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HOMESERVICE MANUALSCHEVROLET2003TRAILBLAZER 4.2 S, 4WDREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 138 (ENGINE CONTROLS REMOVAL & INSTALLATION)FUEL SYSTEMS (CNG ENGINE)LOW PRESSURE LOCK-OFF SOLENOIDREMOVAL & INSTALLATION
2003 Chevrolet TrailBlazer 4.2 S, 4WD

Removal & Installation

2003 Chevrolet TrailBlazer 4.2 S, 4WDSECTION Removal & Installation
WARNING: This page is about a different car, the 2002 Pontiac Sunfire and 2002 Chevrolet Cavalier. However, it is still accessible from the selected car via links, so may be relevant.
  1. Low Pressure Lock-off (LPL) solenoid is located in the Gas Distribution Adapter (GDP). See Figure. Disconnect negative battery cable. Disconnect LPL electrical connector. Remove harness clip from mounting bracket. Disconnect fuel lines and remove LPL inlet and outlet fittings. Remove LPL-to-bracket mounting bolts and remove LPL.
  2. During installation, apply pipe thread sealant to threads of fuel inlet/outlet fittings before installation. DO NOT use teflon tape. Use new "O" rings lubricated with petroleum jelly for all applications. Install LPL solenoid on bracket. Align LPL inlet fitting port to CNG fuel inlet line. Install LPL mounting bolts and tighten to 108 INCH lbs. (12 N.m). Install LPL inlet fitting and tighten finger-tight plus 1-3 turns. Install LPL outlet fitting. Align LPL outlet fitting to LPL to LPR line and tighten fuel outlet fitting finger-tight plus 1-3 turns. Connect fuel line inlet and outlet fittings and tighten to 18 ft. lbs. (24 N.m). Install harness clip to mounting bracket and connect LPL electrical connector. Connect negative battery cable. Start engine. Using Ultrasonic Leak Detector (J 41416), check for CNG fuel leaks at each serviced fitting.
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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.