How Do I Replace a Fuel Injector on a 2003 Chevrolet TrailBlazer With a 4.2 Engine?

Written by cayden conor
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How Do I Replace a Fuel Injector on a 2003 Chevrolet TrailBlazer With a 4.2 Engine?
(Zedcor Wholly Owned/ Images)

Replacing a fuel injector on a 2003 Chevrolet Trailblazer 4.2-litre engine involves removing the entire fuel rail. If you have not tried to clean the fuel injectors, you should try cleaning them first, with a fuel cleaning system available at any auto-parts dealer. Should that fail, or should you have a “hard” failure, when a fuel injector is broken instead of clogged, check all the injectors so all the bad ones can be replaced at this time.

Skill level:

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Things you need

  • Rags
  • Carburettor cleaner
  • Set of wrenches
  • Set of sockets
  • Torque wrench (inch-pounds)

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  1. 1

    Relieve the pressure in the fuel system by removing the fuel pump relay, located in the relay box near the driver’s-side fender well. The cover of the relay box shows you which injector is the fuel pump injector. Remove the relay, then crank the Trailblazer over a couple times.

  2. 2

    Clean the fuel rail with carburettor cleaner and rags. Remove the battery ground cable and set it aside, ensuring that it does not touch metal.

  3. 3

    Remove the intake manifold by unbolting it and lifting it off the engine. Lay rags in the space left by the intake manifold, so that debris does not fall into the engine. Using the appropriate wrench, remove the fuel feed and return pipes.

  4. 4

    Loosen the clamp on the fuel pressure regulator vacuum line, the pull the line off the regulator. Remove the fuel feed and return pipes using the appropriate wrench. Unplug each fuel injector’s electrical connector by pushing in on the plastic tabs and lifting the plug out of the injector. Unbolt the fuel rail retaining bolts and lift the rail off the engine.

  5. 5

    Pry the injector’s retaining clip off with your fingers or a screwdriver. Only remove those clips for the fuel injectors you are replacing. Pull the injector off the fuel rail.

  6. 6

    Oil the new injector O-ring seats with engine oil. Slide the new O-ring on the injector (each injector comes with a new O-ring and retainer clip). Snap the new retainer clip onto the injector.

  7. 7

    Push the injector into its socket on the fuel rail with the connector facing outward. Make sure the retainer clip locks on the flange on the fuel rail injector socket. Gently place the fuel rail on the engine, lining up the fuel injectors. If one of the injectors touches the engine, lift the rail off and make sure that no debris got onto the end of the injector. If it did, clean off the bottom of the injector with carburettor cleaner.

  8. 8

    Tighten the fuel rail retaining bolts to 89 inch-pounds of torque. Reattach the fuel feed and return lines on the rail. Plug in the fuel injectors’ electrical connectors. Replace the vacuum line on the fuel pressure regulator. Reinstall the intake manifold and the battery cable. Plug the fuel pump relay in. Turn the engine on for two seconds, then off for 10 seconds to prime the fuel system. Start the Trailblazer and check for leaks.

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