This procedure covers the removal and replacement of a single fuel injector on the 6.7L Cummins diesel engine, including fuel system depressurization and injector hold-down removal.

Warnings

Tools required

Parts

• Fuel injector × 1 — Use OEM specification
• Fuel line O-rings × 2 — Use OEM specification
• Injector hold-down bolt × 1 — Use OEM specification
• Injector copper crush washer × 1 — Use OEM specification

Preparation

1. Ensure engine is completely cool before beginning work
2. Park vehicle on level surface and engage parking brake
3. Disconnect negative battery cable to prevent accidental starter engagement
4. Clean the engine cover and valve cover area thoroughly to prevent dirt from entering fuel system
5. Place drain pan under work area to catch fuel spillage
6. Have fire extinguisher readily available

Procedure

1. 1

   Remove engine cover
   Remove the engine cover by loosening the mounting screws. Lift the cover straight up and set aside in a clean area.
   Torque spec

   Cover Screws15 Nm (11 lb-ft)
2. 2

   Relieve fuel system pressure
   Turn the ignition key to the ON position (do not start) to activate the fuel pump, then immediately turn OFF. Repeat this cycle 3-4 times to reduce fuel rail pressure. Wait 2 minutes for pressure to dissipate further.
   ⚠️Even after this procedure, some residual pressure will remain. Be prepared for fuel spray when disconnecting lines.
3. 3

   Disconnect fuel supply line to affected injector
   Using the appropriate fuel line disconnect tool, carefully disconnect the high-pressure fuel supply line from the fuel rail to the injector being replaced. Have shop towels ready to catch fuel spillage. Cover the open fuel rail port with a clean shop towel.
   ⚠Some fuel will drain from the line. Immediately wipe up any spilled fuel.
   Torque spec

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

   Disconnect injector electrical connector
   Press the release tab and disconnect the electrical connector from the injector. Move the wiring harness aside to provide clearance.
   ℹ️Note the connector orientation for correct reassembly.
5. 5

   Disconnect injector return line
   Loosen the hose clamp and carefully disconnect the fuel return line from the injector. Have a shop towel ready as some fuel will drain. Cap or plug the return line to prevent contamination.
   Torque spec

   Hose Clamps3 Nm (2 lb-ft)
6. 6

   Remove injector hold-down hardware
   Remove the injector hold-down bolt and clamp that secures the injector to the cylinder head. Keep these components together if they will be reused (replace bolt per service manual recommendations).
7. 7

   Extract fuel injector
   Carefully pull the injector straight up and out of the cylinder head bore. If the injector is stuck, use an injector puller tool to avoid damage. Do not pry or rock the injector as this can damage the bore or break the injector tip.
   ⚠If injector tip breaks off in cylinder, the cylinder head must be removed for extraction. Use proper extraction technique.
8. 8

   Clean injector bore
   With the injector removed, carefully clean the injector bore in the cylinder head using a brass brush or specialized injector bore cleaning tool. Remove all carbon deposits and old copper washer residue. Use compressed air to blow out any debris, being careful not to let debris fall into the cylinder. Stuff a clean lint-free shop towel into the injector bore temporarily to prevent contamination.
   ⚠Do not allow any debris to fall into the combustion chamber or fuel passages.
9. 9

   Prepare new injector
   Remove the new injector from its packaging. Install a new copper crush washer onto the injector tip. Inspect all O-rings on the injector body for damage. Verify the injector part number matches the cylinder position being serviced.
10. 10

    Install new injector
    Remove the protective towel from the injector bore. Carefully lower the new injector straight down into the cylinder head bore, ensuring the copper washer seats properly. Push down firmly but gently until the injector is fully seated and the hold-down clamp can be positioned.
11. 11

    Install hold-down hardware
    Position the injector hold-down clamp over the injector body. Install the hold-down bolt and tighten to the specified torque. Ensure the injector does not rotate during tightening.
    Torque spec

    Mounting Bolts37 Nm (27 lb-ft)
12. 12

    Reconnect fuel return line
    Connect the fuel return line to the injector and secure with the hose clamp. Tighten the clamp to specification.
    Torque spec

    Hose Clamps3 Nm (2 lb-ft)
13. 13

    Reconnect fuel supply line
    Install new O-rings on the fuel line fitting (lubricate lightly with clean diesel fuel). Connect the high-pressure fuel supply line to the injector and tighten to specification using a torque wrench.
    ⚠Always use new O-rings. Old O-rings will leak under high pressure.
    Torque spec

    Fuel Line Fittings25 Nm (18 lb-ft)
14. 14

    Reconnect electrical connector
    Connect the electrical connector to the injector, ensuring it clicks into place securely. Verify the connector lock is fully engaged.
15. 15

    Prime fuel system and check for leaks
    Reconnect the negative battery cable. Turn the ignition key to ON position (do not start) for 10 seconds, then OFF. Repeat this cycle 4-5 times to prime the fuel system. Inspect all fuel connections for leaks. Start the engine and allow it to idle while observing for any fuel leaks. Check injector operation for smooth idle.
    ⚠If any fuel leaks are observed, immediately shut off the engine and correct the issue before continuing.

Reassembly

1. Reinstall engine cover and torque cover screws to specification
2. Wipe down all surfaces to remove any fuel residue
3. Dispose of old injector and contaminated shop towels according to local environmental regulations

Verification

• Start engine and verify smooth idle with no misfires on the replaced cylinder
• Check for fuel leaks at all connection points while engine is running
• Scan for diagnostic trouble codes to ensure no injector-related faults are present
• Test drive vehicle to verify normal operation under load
• Monitor fuel pressure readings if scan tool is available to confirm proper system operation

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