This procedure removes and replaces the fuel pump module assembly located inside the fuel tank of a 2021-2024 Ford F-150 with the 3.5L EcoBoost engine, requiring fuel system depressurization and tank access.

Warnings

Tools required

Parts

• Fuel pump module assembly × 1 — Motorcraft PFS-591 or equivalent OEM
• Fuel pump lock ring seal/gasket × 1 — Use OEM specification
• Fuel line O-rings × 2 — Use OEM specification
• Access cover gasket (if equipped) × 1 — Use OEM specification

Preparation

1. Park vehicle on level ground outdoors or in a well-ventilated garage. Engage parking brake.
2. Ensure fuel tank is less than 1/4 full. If tank is fuller, use approved fuel transfer pump to remove excess fuel into approved containers.
3. Disconnect negative battery terminal and wait 10 minutes to allow fuel pump control module to discharge.
4. Remove rear seat bottom cushion by pulling firmly upward on front edge to disengage retaining clips.
5. Check for fuel pump access panel in floor beneath rear seat. If no access panel is present, tank lowering will be required (not covered in this base procedure).
6. Relieve fuel system pressure: Remove fuel pump fuse (fuse 27 in battery junction box), reconnect battery briefly, attempt to start engine and let it run until it stalls, then crank for 5 seconds. Disconnect battery again.
7. Place drain pan and shop towels under work area to catch residual fuel.
8. Ensure work area is free of ignition sources and fire extinguisher is accessible.

Procedure

1. 1

   Remove fuel pump access cover
   Locate the fuel pump access cover in the floor pan beneath the rear seat. Use appropriate screwdriver or socket to remove the access cover screws. Carefully lift the access cover and set aside with gasket (if reusable). Clean any debris from around the fuel pump module opening to prevent contamination from entering the tank.
   Torque spec

   Access Cover Screws5 Nm (3 lb-ft)
2. 2

   Disconnect electrical connector
   Locate the fuel pump module electrical connector. Press the locking tab and disconnect the connector from the fuel pump module. Move the connector aside to prevent damage. Inspect the connector terminals for corrosion or damage; clean or replace if necessary.
   ⚠Do not pull on wires; use the connector body to disconnect. Damaged connectors can cause fuel pump failure or check engine lights.
3. 3

   Disconnect fuel supply line
   Using the appropriate fuel line disconnect tool, release the fuel supply line from the fuel pump module. Press the disconnect tool into the fitting while pulling the line away from the module. Expect residual fuel spillage; use shop towels to contain. Inspect the line for damage and the O-ring for wear.
   ⚠️Residual fuel under pressure may spray when disconnecting. Keep face and body clear of the connection point. Wear safety glasses.
4. 4

   Disconnect fuel return/vapor lines (if equipped)
   If your fuel pump module has additional return or vapor lines, disconnect them using the same procedure as the supply line. Some configurations use quick-disconnect fittings, others may have threaded connections. Keep track of which line goes where; take a photo if needed for reference during reassembly.
   ℹ️Not all configurations have separate return lines. The 2021-2024 F-150 typically uses a returnless fuel system, but verify your specific configuration.
5. 5

   Remove fuel pump lock ring
   Install the fuel pump lock ring tool onto the lock ring tabs. The lock ring turns counterclockwise to remove. Tap the tool handle sharply with a plastic mallet or strike it firmly by hand to break the lock ring free. Once loose, turn the lock ring counterclockwise until it can be lifted out. Remove and inspect the lock ring seal/gasket; it must be replaced.
   ⚠The lock ring may be tight due to fuel varnish or corrosion. Do not use excessive force or steel hammers that could create sparks. Use controlled strikes with plastic tools only.
   Torque spec

   Fuel Pump Lock Ring78 Nm (58 lb-ft)
6. 6

   Remove fuel pump module assembly
   Carefully tilt and lift the fuel pump module out of the tank opening. The module has a long fuel level sender arm that must be angled to clear the opening. Work slowly to avoid bending the sender arm or damaging the fuel level float. Expect approximately 1-2 cups of fuel to drain from the module; have drain pan ready. Once clear, set the old module on shop towels in the drain pan.
   ⚠The fuel level sender arm is fragile. Bending it will cause inaccurate fuel gauge readings. Tilt the module at approximately 45 degrees as you lift.
7. 7

   Clean tank opening and inspect
   Using clean, lint-free shop towels, wipe the fuel tank opening flange clean. Remove any old gasket material, dirt, or debris. Inspect the tank opening for cracks, corrosion, or damage. Look inside the tank with a flashlight for debris or contamination. The sealing surface must be smooth and clean for proper seal.
   ℹ️Do not allow any debris to fall into the fuel tank. Contamination can damage the new fuel pump or clog injectors.
8. 8

   Prepare new fuel pump module
   Remove the new fuel pump module from packaging. Install the new lock ring seal/gasket onto the fuel pump module flange, ensuring it seats properly in the groove. Verify the fuel level sender arm moves freely and the float is intact. Check that all electrical connections on the new module match the old unit. Compare the new module to the old one to confirm correct replacement part.
   ℹ️Some replacement modules come with the strainer/filter pre-installed; others require transfer from the old module. Verify before installation.
9. 9

   Install new fuel pump module
   Carefully lower the new fuel pump module into the fuel tank opening, tilting at approximately 45 degrees to allow the fuel level sender arm to clear. Rotate the module to align the orientation marks or tabs with the tank markings. Once fully seated, verify the module is properly positioned and the seal is evenly compressed around the entire perimeter. The module should sit flush against the tank.
   ⚠Improper alignment will prevent the lock ring from threading correctly and may damage the seal, causing fuel leaks.
10. 10

    Install and torque lock ring
    Place the lock ring over the fuel pump module and engage the threads by turning clockwise by hand. Install the lock ring tool and turn clockwise to tighten. Torque the lock ring to specification using the torque wrench and lock ring tool. Verify the seal is evenly compressed and the module does not rotate. The lock ring should be tight against the tank flange uniformly around its circumference.
    ⚠Under-torquing will cause fuel leaks; over-torquing can crack the module flange or tank. Use precise torque value.
    Torque spec

    Fuel Pump Lock Ring78 Nm (58 lb-ft)
11. 11

    Connect fuel lines with new O-rings
    Install new O-rings on all fuel line fittings; lightly lubricate with clean gasoline or approved fuel system lubricant. Push the fuel supply line onto the module fitting until it clicks into place. Tug firmly on the line to verify it is locked. Reconnect any return or vapor lines in their original positions. If lines have threaded fittings, torque to specification.
    ⚠Reusing old O-rings will result in fuel leaks. Always use new O-rings on fuel system connections.
    Torque spec

    Fuel Line Fittings25 Nm (18 lb-ft)
12. 12

    Connect electrical connector
    Reconnect the electrical connector to the fuel pump module, ensuring it clicks firmly into place. Verify the locking tab is fully engaged. Gently tug on the connector to confirm it is secure. Ensure no wires are pinched or stressed.
    ℹ️A loose electrical connection will cause intermittent fuel pump operation, starting problems, or check engine lights.
13. 13

    Reinstall access cover
    If the access cover gasket is damaged or compressed, install a new gasket. Position the access cover over the opening, aligning all screw holes. Install all access cover screws and torque to specification in a cross-pattern to ensure even sealing. Verify the cover is flush and properly sealed.
    Torque spec

    Access Cover Screws5 Nm (3 lb-ft)
14. 14

    Reconnect battery and prime fuel system
    Reconnect the negative battery terminal. Reinstall the fuel pump fuse. Without starting the engine, turn the ignition key to ON position (do not crank) for 5 seconds, then OFF. Repeat this cycle 4-5 times to allow the fuel pump to prime the system and build pressure. Check all connections under the access cover for fuel leaks during priming.
    ⚠️Immediately wipe up any fuel leaks. If significant leakage occurs, disconnect battery and repair the leak before proceeding.

Reassembly

1. Reinstall rear seat bottom cushion by aligning the rear hooks first, then pressing down firmly on the front edge until retaining clips engage.
2. Verify all tools and parts have been removed from the vehicle.
3. Dispose of old fuel pump module and contaminated fuel according to local environmental regulations.

Verification

• With the vehicle outdoors or in a well-ventilated area, start the engine and let it idle. Listen for unusual fuel pump noises or engine performance issues.
• Check the fuel pump access area and all visible fuel lines for leaks. Look for fuel stains, drips, or fuel odor.
• Verify the fuel gauge reads correctly and moves appropriately as fuel is consumed.
• Test drive the vehicle and verify normal acceleration, no hesitation, and no check engine light. Monitor fuel pressure if scan tool is available (should be 55-65 PSI at idle for 3.5L EcoBoost).
• After test drive, recheck all connections for leaks when the system is hot and at full operating pressure.
• If any fuel leaks are detected, immediately shut off the engine, disconnect the battery, and repair the leak before operating the vehicle.

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