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, a critical fuel system component operating at extremely high pressures.

Warnings

Tools required

Parts

• High-pressure fuel line assembly × 1 — Use OEM Ford fuel line for 3.5L EcoBoost
• Fuel line O-rings × 4 — Included with OEM line or separate kit
• Fuel line retaining clips × 2 — Reuse if undamaged, replace if worn

Preparation

1. Park vehicle on level ground in well-ventilated area away from all ignition sources
2. Ensure fuel tank is no more than half full to minimize spillage
3. Disconnect negative battery terminal and wait 2 minutes for systems to power down
4. Place fire extinguisher within immediate reach
5. Prepare drip pans and shop towels for fuel spillage
6. Allow engine to cool completely if recently running (minimum 2 hours)
7. If using a lift, raise vehicle and secure on jack stands with rear wheels supported

Procedure

1. 1

   Relieve fuel system pressure
   Locate the fuel pressure test port on the fuel rail (driver's side of engine). Remove the Schrader valve cap. Attach fuel pressure gauge. Slowly open the valve to bleed pressure into gauge reservoir or collection container. Monitor gauge until pressure reads zero PSI. Close valve and remove gauge. This step is CRITICAL - do not skip or rush.
   ⚠️Fuel will spray from test port under extreme pressure if not relieved slowly. Keep face and body clear of the valve. Wear safety glasses.
2. 2

   Access engine compartment fuel connections
   Open hood and locate the high-pressure fuel line at the fuel rail on the driver's side of the engine. The line runs from the fuel rail toward the firewall and down to the fuel pump. Remove the plastic engine cover if equipped by pulling upward on the cover - it is retained by grommets. Identify both the fuel rail connection point and the routing of the line toward the underbody.
   Torque spec

   Cover Screws12 Nm (9 lb-ft)
3. 3

   Disconnect fuel rail connection
   Clean area around fuel rail fitting thoroughly with shop towel. Place drip pan beneath connection. Using appropriate line wrench, loosen the high-pressure line fitting at the fuel rail connection. Note: This is a threaded metal fitting, NOT a quick-disconnect. Turn counterclockwise while holding fuel rail steady. Once loose, unthread by hand and allow residual fuel to drain into pan. Immediately cap or plug the open fuel rail port to prevent contamination.
   ⚠Residual fuel will drain from this connection despite pressure relief. Keep drip pan positioned and have towels ready.
   Torque spec

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

   Remove line mounting brackets
   Follow the fuel line from the fuel rail toward the firewall. Locate bracket(s) securing the line to the engine or chassis. Remove bracket bolts using appropriate socket. Some models have 1-2 brackets securing the high-pressure line. Keep hardware organized for reinstallation.
   Torque spec

   Bracket Bolts23 Nm (17 lb-ft)
5. 5

   Access underbody fuel pump connections
   Working underneath the vehicle (lift or jack stands required), locate the fuel pump module on top of the fuel tank near the driver's side rear wheel area. The high-pressure line exits the pump module and routes forward along the frame rail. Clean the area around the pump connection to prevent contamination. Position drip pan beneath the connection point.
   ⚠️Ensure vehicle is securely supported on jack stands if not using a lift. Never work under a vehicle supported only by a jack.
6. 6

   Disconnect fuel pump module connection
   At the fuel pump module, identify the high-pressure line fitting. This may be a threaded connection or a special quick-connect fitting depending on model year. For threaded: use line wrench to loosen fitting counterclockwise. For quick-connect: use appropriate fuel line disconnect tool, pressing in on the release tabs while pulling the line straight out. Allow residual fuel to drain into pan. Cap or plug both the pump port and the line end immediately.
   ⚠Do not use standard open-end wrenches on fuel line fittings as they will round off the hex. Use only line wrenches (flare nut wrenches).
   Torque spec

   Fuel Line Fittings25 Nm (18 lb-ft)
7. 7

   Remove high-pressure fuel line
   Trace the entire fuel line routing from pump to rail. Note the exact path, including any clips or routing guides along the frame rail and through the engine bay. Release any additional clips securing the line. Carefully remove the complete fuel line assembly from the vehicle. Inspect the old line for signs of damage, chafing, or corrosion that may have caused failure.
   ℹ️Take photos of the routing path before removal to ensure correct installation of the new line.
8. 8

   Prepare new high-pressure fuel line
   Remove new fuel line from packaging. Verify part number matches vehicle application for 2015-2020 F-150 3.5L EcoBoost. Inspect new O-rings at both connection points - replace with new O-rings even if line comes with O-rings installed (use fresh ones from kit). Lightly lubricate O-rings with clean engine oil or fuel-safe lubricant. Do NOT use petroleum jelly or non-compatible lubricants.
   ⚠Using incorrect fuel line or damaged O-rings will cause high-pressure fuel leaks. Verify part compatibility before installation.
9. 9

   Install new fuel line assembly
   Route the new high-pressure fuel line along the exact path as the original, from fuel pump module connection point forward to the fuel rail. Ensure line does not contact any sharp edges, moving components, or heat sources. The line must have adequate clearance from exhaust components. Verify routing matches photos taken during removal. Secure line in any factory routing clips or guides along the frame rail.
   ⚠Improper routing can cause line chafing, leading to catastrophic fuel leak under high pressure. Route exactly as original equipment.
10. 10

    Connect fuel pump module end
    Remove caps/plugs from fuel pump module port and new line end. Verify O-ring is properly seated in line fitting. For threaded connection: thread fitting onto pump module by hand until snug, then torque to specification using line wrench. For quick-connect: push fitting straight onto port until you hear/feel a positive click, then pull back to verify it is locked. Install any retaining clips if applicable.
    ⚠Cross-threading the high-pressure fitting will cause immediate failure. Thread by hand first to ensure proper alignment before using wrench.
    Torque spec

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

    Install line mounting brackets
    Position the line in any chassis or engine mounting brackets. Install bracket bolts and torque to specification. Ensure brackets hold line securely but do not pinch or deform the line. Verify line still has proper clearance from all moving and hot components after brackets are tightened.
    Torque spec

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

    Connect fuel rail end
    Remove caps/plugs from fuel rail port and line fitting. Verify new O-ring is properly seated. Thread the high-pressure line fitting onto the fuel rail connection by hand, turning clockwise. Once hand-tight, use line wrench to torque to specification. Hold the fuel rail steady with another wrench if needed to prevent stress on rail mounting points.
    ⚠Over-torquing can damage the fuel rail or fitting. Under-torquing will cause high-pressure leaks. Use calibrated torque wrench and verify specification.
    Torque spec

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

    Perform initial leak check
    Before starting engine, reconnect negative battery terminal. Turn ignition key to ON position (do not start engine). The fuel pump will prime for approximately 2 seconds. Listen for pump activation. Turn key OFF, wait 5 seconds, then turn to ON again. Repeat this cycle 3-4 times to build fuel pressure. While system is pressurized, carefully inspect all connection points with flashlight, looking for any fuel seepage or wetness. Check both the fuel rail connection and the pump module connection.
    ⚠️If ANY fuel leak is observed, immediately turn ignition OFF, relieve fuel pressure, and correct the issue before proceeding. Do not attempt to start engine with a fuel leak present.
14. 14

    Start engine and verify operation
    If no leaks were observed during priming, start the engine. Allow it to idle. Monitor both fuel line connections closely for any signs of leakage. Engine may run slightly rough for the first few seconds as air is purged from the system. Listen for any unusual noises from the fuel pump or fuel system. Allow engine to reach normal operating temperature while continuing to monitor for leaks.
    ⚠️If ANY fuel leak appears after starting engine, immediately shut off engine, evacuate area, and allow fuel vapors to dissipate before investigating. A high-pressure fuel leak can spray fuel onto hot exhaust components.
15. 15

    Final inspection and test drive
    With engine at operating temperature, perform final visual inspection of all fuel line connections and routing. Check that line has proper clearance and is secured in all brackets. Reinstall plastic engine cover if equipped. Test drive vehicle under normal operating conditions. Monitor for any fuel odor, rough running, or fuel pressure-related fault codes. After test drive, perform final cold inspection of all connections for any seepage.
    Torque spec

    Cover Screws12 Nm (9 lb-ft)

Reassembly

1. Ensure all fuel line connections are torqued to specification and inspected for leaks
2. Verify high-pressure fuel line is properly routed with adequate clearance from heat and moving components
3. Confirm all mounting brackets are installed and secure
4. Reinstall engine covers removed during the procedure
5. Clean up any spilled fuel and properly dispose of contaminated shop towels per local regulations

Verification

• Perform key-on prime cycle 3-4 times and inspect all connections for leaks with system pressurized
• Start engine and verify smooth idle with no fuel odor or visible leaks at operating temperature
• Check for diagnostic trouble codes related to fuel pressure using scan tool
• Test drive vehicle under various load conditions and verify normal performance
• Perform final cold inspection after test drive, checking for any delayed seepage at connection points
• Monitor fuel trims using scan tool to verify system is operating within normal parameters (should be within ±10%)

Related trouble codes on this vehicle

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