1991 mitsuishi Montero

The in-line fuel filter is located under the vehicle on the inside of the RH frame rail at the firewall.

FUEL FILTER REPLACEMENT

Reduce the internal pressure of the fuel pipes and hoses by completing the following operations:
Disconnect the fuel pump harness connector.
Start and run the engine until it stalls, then turn the ignition switch to OFF.
Disconnect the battery negative terminal.
Connect the fuel pump harness connector.
In-line Fuel Filter Removal

Remove the eye bolts while holding the fuel filter nuts securely. CAUTION : Cover with a shop towel to avoid gasoline from splashing.
Remove the fuel filter mounting clamp bolt, then remove the fuel filter from the clamp. NOTE : Be careful not to lose the flat washers. These washers function as gaskets and must be present on re-assembly to prevent leaks.
Torque the fuel filter to the main fuel line.

The filter is located under the vehicle on the driver's side, below
seating area. It's in front of fuel tank mounted on chassis in fuel line.

If the engine is fuel injected (and I believe it is on the 91. It has been awhile) it will have banjo fittings that unbolt. If it has a carb, the filter will just have clamps holding it in place.

If fuel injected, remove the carpet in the cargo area and lift up the floor cover to remove the fuel pump access cover. Unplug the fuel pump harness connector, then start and run the engine until it stalls to reduce the fuel pressure. Next, remove both banjo fittings from each end of the fuel filter and unbolt the filter from the mount. Check the fitting washers and replace if damaged. Tighten both fittings to 25 ft lbs. Reconnect the fuel pump wiring and put everything back together.

If you have a carb and the vehicle is not fuel injected, there is no need to disconnect the fuel pump power. A small amount of fuel will leak, but cover it with a rag when removing it so you don't get it on yourself. Also, always protect your eyes. I have attached a picture of both types of fuel filters and the fuel pump access port.

Let me know if you have questions and if this helps.

Joe