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How-To: Replace The Fuel Filter On A '91 Ls400


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Hi guys and gals,

First and foremost, I'm excited to join such a kind, knowledgeable and large community of Lexus owners! :) I hope to converse with all of you at some point or another in the near future.

And now onto my first post! I just got around to replacing the fuel filter in my mother's '91 LS400 and I decided to share a nice little write-up on the job for you. Keep in mind that it's really elementary so if you guys have any supplemental info that you'd like to add then please feel free to! :ph34r:


3/8-inch drive ratchet

3/8-inch drive sockets

Drip pan (Autozone has cheap, decent quality ones)

Metric open-end wrenches

New fuel filter Part# 300-50020 (I bought a $35 OEM one from

1) Park the Lexus LS400 in a ventilated area such as outside. Walk to the rear of the car and remove the gas cap.

2) Look under the driver side of the Lexus near the front of the driver-side rear tire and locate the fuel filter. The fuel filter is near the driver-side frame of the car. There is also a safety guard below the fuel filter.

3) Remove the bolts from the safety guard with the 3/8-inch drive ratchet and a 3/8-inch drive socket. Pull the safety guard down and place it to the side of the car.

4) Position the drip pan under the fuel filter. Then, place a open-end wrench onto one of the nuts that is built onto the fuel filter. Turn the fuel line nut with another open-end wrench counterclockwise to loosen and remove the fuel line from the fuel filter while holding the other wrench as a back-up. Do this to both fuel lines. Pull the fuel lines out of the fuel filter.

5) Remove the two small nuts from the fuel filter bracket with the 3/8-inch drive ratchet and a socket. Then, pull the fuel filter out of the bracket and put it into the drip pan.

6) Put the new fuel filter into the bracket with the flow arrow pointing towards the front of the Lexus LS400. The flow arrow is stamped to the side of the fuel filter.

7) Position the bracket back over the fuel filter and screw the two nuts back on. Tighten the nuts down tight with the ratchet and socket.

8) Screw both fuel lines into the fuel filter ports. Tighten the fuel line nuts with the open-end wrench while holding the fuel filter nuts with another open-end wrench as a back-up. Once the fuel lines are tight, slide the drip pan out from under the Lexus LS400.

9) Turn the key to the "On" position for five seconds and then back off. Do this three times in a row. Crank the engine on the fourth turn of the ignition. This process is called priming the fuel filter with gas. While the engine is running, inspect the fuel filter for any leaks. Then, turn the engine off.

10) Position the safety guard back over the fuel filter and screw the nuts on. Tighten the nuts down tight with the 3/8-inch drive ratchet and socket

11) You're done! B)

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