This procedure covers the removal and replacement of a single fuel injector on the 3.5L EcoBoost V6 engine, including fuel system depressurization and fuel rail removal.

Warnings

Tools required

Parts

• Fuel injector × 1 — Use OEM specification - Motorcraft CM-5273 or equivalent
• Fuel injector O-ring set × 1 — Upper and lower O-rings for EcoBoost injector
• Fuel line O-rings × 2 — Use OEM specification

Preparation

1. Park vehicle on level surface and engage parking brake
2. Ensure engine is completely cold before starting work
3. Disconnect negative battery cable and wait 5 minutes to allow system capacitors to discharge
4. Remove engine cover by pulling upward on cover to release retaining clips
5. Clean area around fuel rail and injectors with shop towels to prevent debris entry

Procedure

1. 1

   Relieve fuel system pressure
   Locate the fuel pressure test port on the fuel rail (Schrader valve on driver side of fuel rail). Attach fuel pressure gauge with drain hose into catch pan. Open valve to relieve pressure. System pressure should drop to 0 psi. Close valve and remove gauge. Alternatively, remove fuel pump fuse (fuse 27 in battery junction box) and start engine until it stalls, then crank for 5 seconds to ensure depressurization.
   ⚠️Residual fuel will spray from test port. Direct hose into catch pan and wear safety glasses.
2. 2

   Disconnect fuel supply line
   Locate the fuel supply line connection on the driver side of the fuel rail. Using the appropriate size fuel line disconnect tool, push the tool into the connector and pull the fuel line straight off the rail. Have shop towels ready to catch residual fuel. Inspect the O-ring on the line for damage.
   ⚠Even after depressurization, residual fuel will be present in lines and rail.
3. 3

   Disconnect electrical connectors
   Disconnect the electrical connector from the faulty fuel injector by pressing the release tab and pulling straight up. If accessing multiple injectors is easier, disconnect all six injector connectors. Note the connector routing for reassembly.
4. 4

   Remove fuel rail mounting bolts
   Remove the four fuel rail mounting bolts (two on each side of the engine). On the EcoBoost engine, these are 8mm bolts located at the ends of each fuel rail. Keep bolts organized for reinstallation.
   Torque spec

   Fuel Rail Bolts12 Nm (9 lb-ft)
5. 5

   Remove fuel rail assembly
   Carefully pull the fuel rail assembly straight upward to disengage all six injectors from the intake manifold. The injectors may stick in their bores. Apply even upward pressure on both sides of the rail. Once free, lift the entire rail with injectors attached away from the engine. Place on clean work surface with injectors facing upward.
   ⚠Do not pry or rock fuel rail excessively as this can damage injector seals or mounting bores.
6. 6

   Remove faulty fuel injector
   Locate the faulty injector on the fuel rail. Remove the metal retaining clip that secures the injector to the rail by prying upward with a flathead screwdriver or pick tool. Once clip is removed, pull the injector straight out of the fuel rail. Note the orientation of the injector and the position of the upper and lower O-rings.
7. 7

   Prepare new fuel injector
   Remove the new injector from packaging. Install new upper O-ring (larger) into the groove on the injector body near the electrical connector. Install new lower O-ring (smaller) into the groove near the injector tip. Lightly lubricate both O-rings with clean engine oil or gasoline to ease installation. Do not use petroleum jelly or other lubricants.
   ℹ️Ensure O-rings are properly seated in their grooves and not twisted before installation.
8. 8

   Install new injector to fuel rail
   Insert the new injector into the fuel rail bore, ensuring proper orientation (electrical connector should face outward). Push firmly until the injector is fully seated. Install the metal retaining clip by pressing down until it clicks into place, securing the injector to the rail.
9. 9

   Inspect intake manifold injector bores
   Before reinstalling the fuel rail, inspect each injector bore in the intake manifold for debris, damage, or old O-ring material. Clean if necessary with shop towels. Ensure all six bores are clean and dry.
10. 10

    Reinstall fuel rail assembly
    Carefully align all six injectors with their corresponding bores in the intake manifold. Press down evenly on the fuel rail, ensuring all injectors seat fully into the manifold. The rail should sit flush against the mounting surface. Install the four fuel rail mounting bolts finger-tight, then torque in a cross pattern to specification.
    Torque spec

    Fuel Rail Bolts12 Nm (9 lb-ft)
11. 11

    Reconnect fuel supply line
    Install new O-rings onto the fuel supply line if the old ones show any wear. Push the fuel line connector straight onto the fuel rail fitting until you hear and feel a positive click. Gently pull on the line to verify it is locked in place.
    ℹ️Connection must click audibly to ensure proper engagement and prevent fuel leaks.
    Torque spec

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

    Reconnect electrical connectors
    Reconnect the electrical connector to the new fuel injector (and any others that were disconnected) by pushing down until the connector clicks into place. Verify all connections are secure.
13. 13

    Pressure test fuel system
    Reconnect the negative battery cable. Turn the ignition key to the ON position (do not start engine) for 5 seconds, then OFF. Repeat this cycle 3-4 times to prime the fuel system and build pressure. Inspect all fuel connections, the fuel rail, and the new injector area for any signs of fuel leakage. Address any leaks before proceeding.
    ⚠️If any fuel leakage is detected, immediately turn off ignition, relieve pressure, and correct the leak before starting engine.

Reassembly

1. Reinstall engine cover by aligning clips and pressing down until secured
2. Double-check all electrical connectors are fully seated
3. Ensure no tools or shop towels are left in engine bay
4. Verify fuel line connection is secure with no visible fuel weeping

Verification

• Start engine and allow to idle for 2-3 minutes while monitoring for fuel leaks around the new injector and fuel rail connections
• Check for proper engine operation with no misfires or rough idle (a brief rough start may occur as air purges from fuel rail)
• Scan for diagnostic trouble codes with OBD-II scanner to verify no injector or fuel system codes are present
• Perform a test drive and monitor engine performance under various load conditions
• After test drive, perform final visual inspection for any fuel leaks while engine is running and hot

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