Fuel Line - High Pressure

This procedure replaces the high-pressure fuel line between the fuel pump and fuel rail on the 3.5L EcoBoost engine, which operates at extremely high pressures and requires complete fuel system depressurization.

Warnings

Tools required

Parts

• High-pressure fuel line assembly × 1 — Use OEM Ford specification - aftermarket not recommended
• Fuel line O-rings (large) × 2 — Use OEM specification
• Fuel line O-rings (small) × 2 — Use OEM specification

Preparation

1. Ensure engine is completely cold (sitting overnight preferred)
2. Park vehicle on level surface and apply parking brake
3. Place fire extinguisher within immediate reach of work area
4. Ensure work area is well-ventilated with no ignition sources present
5. Disconnect negative battery cable and wait 10 minutes for system capacitors to discharge
6. Remove engine cover by pulling upward on front edge then lifting off rear mounting grommets
7. Locate fuel pump relay in engine compartment fuse box (Relay R3 in box 6)
8. Take photos of fuel line routing and connection points for reference during reassembly

Procedure

1. 1

   Depressurize fuel system completely
   Remove fuel pump relay R3 from engine compartment fuse box. Attempt to start the engine - it should crank but not start or run briefly then stall. Continue cranking for 5-10 seconds after engine dies to ensure fuel rail is completely empty. If engine does not attempt to start, fuel system is depressurized. Reconnect negative battery cable temporarily to proceed with further steps requiring electrical power.
   ⚠️Do not skip this step. Un-depressurized EcoBoost fuel systems can spray fuel with enough force to penetrate skin and cause blindness.
2. 2

   Access high-pressure fuel line at fuel rail
   Locate the high-pressure fuel line connection at the driver-side fuel rail. The line enters from underneath and connects with a threaded fitting. Clean the connection area thoroughly with shop towels to prevent contamination. Place drain pan directly underneath the connection point as residual fuel will leak when disconnected.
   ⚠Even after depressurization, residual fuel remains in lines. Expect fuel spillage.
3. 3

   Disconnect fuel rail end of high-pressure line
   Using appropriate wrench, carefully loosen the fuel line fitting at the fuel rail connection. Hold the fuel rail fitting stationary with a backup wrench to prevent twisting the rail. Once loosened, remove fitting by hand and immediately cap or plug both the line and rail port to prevent contamination. Remove and discard the O-rings from both the line and rail port.
   ⚠Fuel will drain from line and rail. Keep drain pan positioned and have additional towels ready.
   Torque spec

   Fuel Line Fittings25 Nm (18 lb-ft)
4. 4

   Access high-pressure pump connection
   From underneath the vehicle, locate the high-pressure fuel pump mounted on the driver-side cylinder bank. The high-pressure line connects to the pump outlet with a threaded fitting. Clean the connection area thoroughly. Position drain pan underneath as significant fuel spillage will occur.
   ℹ️May require raising vehicle for better access depending on your mobility and lighting. If raising vehicle, use proper jack stands - never work under a vehicle supported only by a jack.
5. 5

   Disconnect pump end of high-pressure line
   Using appropriate wrench, carefully loosen the fuel line fitting at the high-pressure pump outlet. Use a backup wrench on the pump fitting to prevent twisting the pump body. Once loosened, remove fitting by hand. Fuel will drain from both the line and pump. Remove and discard the O-rings from both the line and pump port.
   ⚠High-pressure pump contains residual fuel under spring pressure. Expect continuous fuel drip for several minutes.
   Torque spec

   Fuel Line Fittings25 Nm (18 lb-ft)
6. 6

   Release line from mounting brackets
   The high-pressure fuel line is secured to the engine with metal brackets and clips. Working from fuel rail to pump, identify all mounting points. Remove bracket bolts and release line from all clips. Note the exact routing path and bracket positions for new line installation. Take additional photos if needed.
   Torque spec

   Bracket Bolts23 Nm (17 lb-ft)
7. 7

   Remove old high-pressure fuel line
   Carefully maneuver the old fuel line out of the engine bay, noting any tight clearances or specific routing paths around other components. The line must route away from hot exhaust components and moving parts. Inspect the old line for signs of damage, chafing, or leakage to identify what caused failure.
   ℹ️Line routing is critical - it must not contact exhaust manifolds, turbocharger components, or any sharp edges.
8. 8

   Prepare new high-pressure fuel line
   Unpack new fuel line and verify it matches the old line in length, fittings, and configuration. Install new O-rings on both ends of the new line - use only the O-rings provided with the new line or OEM replacement O-rings. Lightly lubricate O-rings with clean engine oil to prevent pinching during installation. Inspect all fittings for damage or debris.
   ⚠Never reuse old O-rings. Always use new O-rings with correct specifications for high-pressure fuel systems.
9. 9

   Install new fuel line and route properly
   Route the new high-pressure fuel line through the engine bay following the exact path of the old line. Ensure the line does not contact exhaust components, sharp edges, or moving parts. Verify adequate clearance to turbocharger, exhaust manifolds, and accessory drive belt. The line should follow its natural curve without forcing or bending.
   ⚠Improper routing can cause line failure from heat or chafing, resulting in dangerous fuel leak under high pressure.
10. 10

    Connect line to high-pressure fuel pump
    Install new O-rings in the high-pressure pump outlet port if not already on the line fitting. Align the fuel line fitting with the pump outlet and hand-thread the connection carefully to avoid cross-threading. Once hand-tight, use torque wrench and backup wrench to tighten to specification. Hold pump fitting stationary while tightening line fitting.
    ⚠️Cross-threading or improper torque will cause high-pressure fuel leak. Verify fitting threads smoothly by hand before using wrench.
    Torque spec

    Fuel Line Fittings25 Nm (18 lb-ft)
11. 11

    Secure line in mounting brackets
    Install the fuel line into all mounting brackets and clips in their original positions. Ensure the line sits properly in each bracket without strain or tension. Install and torque all bracket bolts. Verify the line has adequate clearance from all surrounding components and cannot contact anything during engine vibration.
    ℹ️Line must be properly supported to prevent vibration fatigue failures. Do not skip any mounting brackets.
    Torque spec

    Bracket Bolts23 Nm (17 lb-ft)
12. 12

    Connect line to fuel rail
    Install new O-rings in the fuel rail port if not already on the line fitting. Align the fuel line fitting with the fuel rail connection and hand-thread carefully to avoid cross-threading. Once hand-tight, use torque wrench and backup wrench to tighten to specification. Hold fuel rail fitting stationary while tightening line fitting.
    ⚠️This is the highest stress connection point. Improper installation will cause catastrophic fuel spray under pressure.
    Torque spec

    Fuel Line Fittings25 Nm (18 lb-ft)
13. 13

    Perform initial leak check
    With fuel pump relay still removed, reconnect negative battery cable. Turn ignition key to ON position (do not start engine). The fuel pump should not run with relay removed. Carefully inspect both fuel line connections for any signs of fuel seepage. Check all bracket mounting points and verify no contact with other components. Turn ignition OFF.
    ℹ️Any visible fuel seepage at this stage indicates improper O-ring installation or fitting torque. Do not proceed - repair must be corrected.
14. 14

    Pressurize fuel system and verify connections
    Reinstall fuel pump relay R3. Turn ignition to ON position without starting engine. Fuel pump will run for approximately 2 seconds, pressurizing the system. Immediately inspect all connections closely for leaks. If no leaks visible, cycle ignition OFF then ON two more times. After third pressurization cycle, use clean white shop towel to check around all fittings for any fuel seepage.
    ⚠️System is now at full high pressure (2,175 PSI). Any leak will spray fuel with extreme force. Keep face and body clear of fittings. Have fire extinguisher ready.
15. 15

    Start engine and perform final leak verification
    Start the engine and let it idle. With engine running, carefully inspect all fuel line connections using flashlight and mirror if needed. Check for fuel odor, visible spray, or wetness around fittings. Check underneath vehicle at pump connection. Let engine run for 5 minutes while monitoring. If any leak is detected, immediately shut off engine, depressurize system, and correct the issue.
    ⚠️Running engine creates maximum fuel pressure and heat. Any leak is extremely dangerous. Do not allow anyone to smoke or create sparks near vehicle.

Reassembly

1. Reinstall engine cover by aligning rear mounting grommets first, then pressing down firmly at front clips until fully seated
2. Perform final visual inspection of entire fuel line routing to verify no contact with moving or hot components
3. Verify all tools and parts packaging have been removed from engine bay
4. Clean up any spilled fuel immediately with absorbent material and dispose of properly

Verification

• With engine at operating temperature, inspect all fuel line connections for leaks using flashlight - no fuel odor or wetness should be present
• Check that fuel line has adequate clearance from exhaust components (minimum 1 inch clearance recommended)
• Verify all mounting brackets are secure and fuel line is properly supported along entire length
• Test drive vehicle and monitor for fuel odor, rough running, or check engine light - any of these indicate potential leak or connection issue requiring immediate attention
• After test drive, perform final cold inspection of all connections with engine off for 30 minutes - residual pressure leaks may only appear when system cools

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