Filtering the gasoline leaving the tank before it reaches the engine is the sole responsibility of the fuel filter. Over the course of time, dirt from around the fuel door makes its way into the gas tank and eventually deposits in the fuel filter. This leads to clogging of the fuel filter. A clogged or restricted fuel filter won’t allow enough fuel to pass through it to keep the engine running. The Envoy’s engine may not run at all or may just keep stalling out. You can replace the fuel filter on your 2004 GMC Envoy L6 in 30 minutes or less. The fuel filter mounts under the truck on the right frame well, forward of the gas tank.
Raise the hood on the Envoy and locate your power distribution center. Take the cover off and then use a pair of relay-puller pliers to remove the fuel pump relay. You can remove the relay by hand, but for safety purposes, use the pliers instead.
Open the fuel door and remove the gas cap slowly to depressurize the fuel tank.
Start the engine and allow the truck to run until it stalls out. After the engine stalls, attempt to start it back up three more times. The engine may run again and then quickly stall. By the third attempt, however the engine will have exhausted all of the fuel pressure and any available gasoline.
Disconnect the black (negative) cable from the battery with a socket wrench. Move the cable completely away from its post so accidental contact with the battery or other metal in the engine area doesn’t happen.
Put on your safety glasses and slide under the Envoy head first near the rear driver’s-side tire. Locate the fuel filter on the frame rail. It will have fuel lines connected to it and look like a metal cylinder a bit bigger than a jar of baby food.
Wipe all of the dirt off each fuel line connected to the fuel filter for two feet in both directions using a shop rag. It’s also a good idea to wipe down the old fuel filter too, even though you’re going to remove it.
Place a metal catch pan beneath the fuel filter and then, one at a time, remove the fuel lines from the filter. The quick-connect fitting can be removed by squeezing in the tabs on the fitting while pulling it off the nipple of the fuel filter. (See the Resource link for a complete breakdown on removing quick-connect fittings of all types.)
Loosen the bolt on the clamp holding the fuel filter in place and then slide the filter out of the clamp. Install the new fuel filter back into the clamp and re-tighten the clamp’s bolt until snug. Before you hook the fuel lines back up, make sure the arrow on the fuel filter is pointing toward the engine and not the gas tank.
Connect the fuel lines by pushing each of the quick-connect fittings back onto the new fuel filter’s nipples until you hear them “click” into place. Check their connection by gently pulling on them if you don’t hear a click when connecting both lines.
Place the gas cap back on tightly and then reinstall the fuel pump relay. Secure the negative battery cable back to its post, then start the engine and check for leaks. If no leaks are observed take the Envoy for a test drive.
