High Pressure Fuel Pump

This procedure replaces the high-pressure fuel pump on the 5.9L Cummins diesel engine, including fuel system depressurization, pump removal, and installation with timing verification.

Warnings

Tools required

Parts

• High pressure fuel pump × 1 — Use OEM Bosch CP3 or equivalent for 5.9L Cummins
• Fuel pump mounting gasket/O-rings × 1 — Included with pump or separate kit
• Fuel line crush washers × 4 — Use OEM specification
• Fuel filter/water separator × 1 — Replace during service

Preparation

1. Park vehicle on level ground and engage parking brake
2. Disconnect both negative and positive battery cables to prevent accidental starting
3. Allow engine to cool completely if recently operated (minimum 2 hours)
4. Clean the engine bay area around the fuel pump with degreaser to prevent contamination
5. Place drain pans under the fuel filter and pump area
6. Have adequate lighting available as the pump is located on the driver side of the engine

Procedure

1. 1

   Depressurize fuel system
   Remove the fuel/lift pump relay (or fuse) from the Totally Integrated Power Module (TIPM) to prevent the in-tank lift pump from operating. Even with the engine off, residual pressure exists in the system. Open the fuel filter drain valve slowly to release pressure and drain fuel into a suitable container. Close the drain valve when fuel flow stops. Wipe all connections clean before proceeding.
2. 2

   Remove engine cover and air intake
   Remove the plastic engine cover by lifting upward on the front clips. Loosen the hose clamps on the air intake tube and remove the intake tube from the turbocharger to the airbox to improve access. Move the tube aside and secure it away from the work area.
3. 3

   Disconnect high pressure fuel lines
   Using two wrenches (one to hold the pump fitting, one to loosen the line nut), carefully disconnect the high pressure fuel line from the pump. This is the line going to the fuel rail. Cap all open connections immediately with clean plastic caps to prevent contamination. Expect residual fuel spillage and catch with shop towels. Note the routing and orientation of lines for reinstallation.
   ⚠Even after depressurization, fuel lines contain residual fuel under pressure. Loosen connections slowly and be prepared for fuel spray.
4. 4

   Disconnect fuel supply and return lines
   Disconnect the low pressure fuel supply line from the inlet side of the pump using appropriate fuel line disconnect tools. Disconnect the fuel return line. These are quick-connect fittings on the 2007 model. Cap all openings immediately. Label lines if necessary to ensure correct reconnection.
5. 5

   Disconnect electrical connector
   Locate the electrical connector on the rear of the fuel pump (fuel control actuator). Press the release tab and disconnect the connector. Move the wiring harness away from the pump area to prevent damage during removal.
6. 6

   Remove pump mounting bolts
   Remove the three mounting nuts securing the fuel pump to the gear housing on the front of the engine. Support the pump with one hand while removing the final fastener, as the pump is moderately heavy (approximately 8-10 lbs). Note: These bolts may have thread sealant applied.
7. 7

   Remove high pressure fuel pump
   Carefully pull the pump straight out from the gear housing. The pump drive gear meshes with the engine gear train inside the housing. You may need to rotate the pump slightly while pulling to disengage. Do not pry on the pump body. Once removed, immediately cover the gear housing opening with a clean shop towel to prevent contamination. The CP3 pump is not timed to the engine (fuel delivery is controlled electronically), so pump timing does not need to be indexed; however, avoid rotating the engine unnecessarily while the pump is removed and the gear housing is open.
   ⚠Do not allow the engine to rotate once the pump is removed, as this can disturb the timing relationship between the camshaft and pump drive gear.
8. 8

   Inspect gear housing and clean mounting surface
   With the pump removed, inspect the gear housing opening for metal debris or contamination. If present, this indicates internal wear and further diagnosis is needed. Use compressed air to blow out any debris (shield the opening with a towel to contain debris). Thoroughly clean the pump mounting surface on the gear housing, removing all old gasket material. Clean the mating surface on the new pump as well.
9. 9

   Prepare new pump for installation
   Remove the new pump from its packaging in a clean area. Install new O-rings or gasket onto the pump mounting flange, lightly lubricating with clean diesel fuel. Verify that the pump drive shaft/gear rotates (with expected internal resistance) and is not seized. Check that the fuel control actuator connector matches your original pump.
10. 10

    Install high pressure fuel pump
    Position the new pump at the gear housing opening, aligning the pump drive gear with the engine gear train. The pump can only be installed in one orientation due to the drive gear design. Push the pump into the housing while rotating slightly (approximately 1/8 turn back and forth) until it seats fully against the mounting surface. The pump should sit flush with no gaps.
    ⚠Do not force the pump. If it does not slide in with moderate pressure and slight rotation, remove it and check for obstructions or misalignment.
11. 11

    Install pump mounting bolts
    Install the three mounting bolts through the pump flange into the gear housing. Start all bolts by hand to ensure proper thread engagement. Tighten the nuts in a crossing pattern (not in sequence) to pull the pump evenly into place. Torque mounting nuts to factory specification (not available in database - consult service manual; approximately 24 ft-lbs / 32 N·m, verify before use). Apply thread sealant if specified by pump manufacturer.
12. 12

    Reconnect fuel lines
    Remove caps from fuel line fittings. Install new crush washers on high pressure line fittings. Reconnect high pressure fuel lines to the pump, routing them as noted during removal. Tighten using two-wrench method to prevent twisting the pump fittings. Reconnect low pressure supply and return lines, ensuring quick-connect fittings lock fully into place. Verify security by pulling on each line.
13. 13

    Reconnect electrical connector and reinstall components
    Reconnect the electrical connector to the fuel control actuator on the rear of the pump until it clicks. Tug gently to verify it is locked. Reinstall the air intake tube and tighten hose clamps. Reinstall the engine cover.
14. 14

    Prime fuel system and check for leaks
    Reinstall the fuel pump relay. Reconnect battery cables (positive first, then negative). Without starting the engine, turn the ignition key to the 'Run' position for 15 seconds to allow the lift pump to prime the system. Turn key off, wait 10 seconds, then repeat this cycle 4-5 times. Inspect all fuel connections for leaks. Wipe connections dry and check again.
15. 15

    Start engine and verify operation
    Start the engine. It may take longer than normal to start on the first attempt as the system purges air. Once running, allow the engine to idle for 2-3 minutes while monitoring for fuel leaks and unusual noises. Check for smooth idle operation. Rev the engine slightly to verify throttle response. Immediately shut down if any leaks or abnormal operation is observed.
    ⚠️If any fuel leaks are present during engine operation, shut down immediately. High pressure fuel leaks can spray fuel onto hot engine components causing fire, or penetrate skin causing serious injury.

Reassembly

1. Ensure all fuel line connections are tight and leak-free before operating the vehicle
2. Double-check that all electrical connectors are fully seated and locked
3. Verify that no tools or shop towels were left in the engine compartment
4. Replace the fuel filter/water separator as this service introduces potential contamination risk

Verification

• With engine at operating temperature, verify smooth idle with no misfires or rough running
• Check all fuel connections for leaks with engine running - look for wet spots or fuel odor
• Verify no diagnostic trouble codes are present using a scan tool
• Test drive the vehicle and verify normal acceleration and power delivery under load
• After test drive, perform a final leak inspection of all fuel connections with engine hot
• Monitor fuel pressure at idle and under load with a scan tool if available (should be approximately 5,000-23,000 PSI depending on load)
• Recheck for leaks after 50-100 miles of operation as connections may weep after thermal cycling

Related trouble codes on this vehicle

Codes that commonly send this job to the bay — tap one for symptoms, causes, and diagnostic steps.

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