The fuel pump on the 2001 Ford Focus is connected to the fuel sender unit as a module, and you may need to replace them together. This module is stored within the fuel tank; you remove the tank in order to change the pump/sender unit. Do this with as little fuel in the tank as possible, and you'll also need some special tools. Talk with your mechanic before you try to take on this repair project.
Relieve the fuel system's pressure by removing the No. 12 fuse from the engine compartment's fuse box and running the engine until it stalls. Turn off the ignition and disconnect the negative battery terminal.
Block the front wheels with any solid, sturdy blocks you can find. Raise the car's rear end with the stock jack and support it on axle stands, and then remove both rear wheels with a lug wrench.
Separate the exhaust flange joint by removing the nuts, then unfasten and remove the heat shield; use a flare-nut wrench. Unhook the exhaust system's front and rear mounting rubbers--this requires a special tool from an auto parts store.
Rest the disconnected exhaust on the rear suspension cross member and an axle stand, and move it away from the tank.
Disconnect the filler pipe and vent hose from the tank by loosening their clamps with a screwdriver. Disconnect the charcoal canister by disconnecting its hoses, pressing the metal clip and lifting the canister upward to release it from the clip.
Disconnect the fuel supply hose from the fuel filter intake by prying out the insert on the fitting, then disconnect the return line at the connector near the filter.
Raise a jack with a block of wood on it to support the tank, then unbolt the tank's straps with a wrench and remove them.
Lower the tank slowly with the jack. Disconnect the fuel lines once they are accessible, using a small screwdriver at the quick-connect fitting lugs, and unplug the wiring plug by hand.
Disconnect the fuel lines from the tank if they are still attached, using a small screwdriver to release the fitting lugs at the connections. The supply line's connector has a white band and the return line connector has a red one.
Unscrew and remove the retaining ring, which requires a special tool. An oil filter strap wrench or large slip-joint pliers can work, but the Ford service tool 310-069 is designed for this task.
Withdraw the top cover of the pump/sender unit as far as you can; it is connected by wiring to the unit itself. Turn the unit counterclockwise from inside the tank by hand and withdraw it. Remove the rubber seal from the pump's periphery.
Insert the replacement pump/sender unit into the tank. Twist the unit clockwise by hand once it is fully seated in the tank to lock it in place.
Place the unit's top cover on the opening, and twist it by hand so the arrow on the cover lines up with the arrows on the fuel tank. Place a new rubber seal on the periphery and tighten the retaining ring in place with the same tool you used to remove it.
Connect the fuel lines and the electrical connector to the unit; they should snap into place with their quick-connect fittings.
Reinstall the fuel tank on the Focus, lifting it in place with the jack and bolting the straps in place with the wrench. Reconnect the fuel lines to the fuel filter, and connect the charcoal canister, filler pipe and vent hose to the tank with their clamps and clips.
Connect the exhaust system by reconnecting its mounting rubbers with the same tool as before and mounting the heat shield and exhaust flange with their nuts and the wrench.
Reinstall the wheels with the lug wrench, and lower the Focus with the jack. Reconnect the negative battery terminal. Start the engine and check for leaks.
It is possible to separate the fuel pump from the sender unit if you only need to replace it. Squeeze the lugs at the side below the pump's mounting, using needle-nose pliers, to disconnect the sender unit.