The 1991 Toyota trucks came equipped with a in-line fuel filter that is responsible for keeping clean gas flowing to the engine. The fuel filter has a inner filter inside. As the gas flows through the inner filter's fibers, impurities get trapped inside. The clean gas then travels out through the outlet tube of the fuel filter and flows to the fuel injectors. Replace the fuel filter between 60,000 and 75,000 miles.
Park the 1991 Toyota truck in a ventilated area. Open the hood and secure it in place.
Walk to the rear of the truck and remove the gas cap. This process will relieve the gas pressure off the fuel filter so that gas does not spray everywhere.
Locate the fuel filter on the passenger side of the engine on the inside of the lower passenger-side frame rail. The fuel filter will have a screw-on fuel line coming out of each end.
Slide the drip pan under the truck in the general area of the fuel filter. Move back to the top passenger side of the engine and remove both fuel lines coming out the fuel filter. Each fuel line has a hex-head nut that screws into each end of the fuel filter. Turn the fuel line nuts counterclockwise with a metric open-end wrench to loosen and remove. Then, pull the fuel lines straight out of the fuel filter.
Remove the bolt from the fuel filter bracket with the ratchet and a metric socket. Note the direction of the flow arrow on the side of the fuel filter. This arrow represents the fuel flow through the fuel filter and the arrow on the new fuel filter will have to point in the same direction as the old fuel filter.
Pull the fuel filter out of the engine compartment and put it in the drip pan. Then, mount the new fuel filter bracket to the frame rail with the bolt and tighten the bolt with the ratchet and socket.
Screw both fuel lines to each end of the fuel filter until tight. Then, finish tightening the fuel lines with the open-end wrench. Once the fuel lines are tight, screw the gas cap back on the gas tank.
Turn the ignition key to the accessory position for five seconds and then back off again. Repeat this step two more times. This process will prime the new fuel filter with gas and remove the air from the fuel filter and the fuel lines.
Crank the 1991 Toyota pickup and inspect the new fuel filter for leaks while the motor is running.
Turn the engine off and close the hood. Then, pull the drip pan out from under the truck.
