This procedure addresses a critical error: the 6.7L Cummins diesel engine does not use spark plugs. Diesel engines use compression ignition with glow plugs for cold starts, not spark plugs.

Warnings

Tools required

Parts

• Glow plug (set of 6) × 6 — Mopar 68197867AA or equivalent
• Glow plug connector O-rings × 6 — Use OEM specification
• Engine cover clips (if damaged) × 2 — Use OEM specification

Preparation

1. Ensure engine is completely cold (minimum 2 hours after last operation)
2. Park vehicle on level surface and engage parking brake
3. Disconnect both negative battery cables (dual battery system)
4. Allow glow plug system to cool for safety
5. Gather all tools and parts before beginning
6. Take photos of engine cover and wiring routing for reference

Procedure

1. 1

   Remove engine cover
   Release the engine cover retaining clips by pulling upward firmly. The cover is held by friction clips at multiple points. Lift the cover straight up and away from the engine bay. Inspect clips for damage and replace if broken.
   Torque spec

   Engine Cover Clips4 Nm (3 lb-ft)
2. 2

   Access glow plug harness
   Locate the glow plug controller module on the driver's side of the engine. Trace the wiring harness from the controller to each of the six glow plugs. The glow plugs are located on the intake side of the cylinder head, one per cylinder. Remove any wiring looms or clips holding the harness in place.
   ℹ️Take photos of harness routing before disconnecting to ensure proper reinstallation
3. 3

   Disconnect glow plug electrical connectors
   Disconnect the electrical connector from each glow plug by pressing the release tab and pulling straight up. Inspect each connector and O-ring for damage, corrosion, or burning. Clean connectors with electrical contact cleaner if corroded. Mark or photograph the cylinder numbering for reference.
   ⚠Damaged connectors can cause glow plug system faults. Replace any connectors showing signs of heat damage or corrosion
4. 4

   Test glow plug resistance
   Before removal, use a multimeter to test each glow plug resistance. Connect the multimeter between the glow plug terminal and engine ground. A functional glow plug should read 0.5-2.0 ohms. Record readings for each cylinder. An open circuit (infinite resistance) indicates a failed glow plug.
   ℹ️This diagnostic step helps identify which glow plugs need replacement and verifies the issue before disassembly
5. 5

   Apply penetrating oil
   Spray penetrating oil around the base of each glow plug where it threads into the cylinder head. Allow the penetrating oil to soak for at least 30 minutes. For engines with high mileage or known glow plug issues, allow several hours of soaking time. This prevents glow plugs from breaking during removal.
   ⚠️Breaking a glow plug off in the cylinder head requires cylinder head removal for extraction. Take your time with removal
6. 6

   Remove glow plugs
   Using a 10mm deep socket or dedicated glow plug socket, carefully remove each glow plug. Apply steady, even pressure while turning counterclockwise. If significant resistance is felt, stop and apply more penetrating oil. Remove each glow plug completely and inspect the threads and tip condition. Note any plugs with damaged tips or excessive carbon buildup.
   ⚠If a glow plug will not turn after several attempts with penetrating oil, consider professional assistance to prevent breakage
7. 7

   Inspect cylinder head bores
   Inspect each glow plug bore in the cylinder head for carbon deposits, thread damage, or coolant seepage. Use a wire brush to clean threads if carbon buildup is present. Check for any signs of coolant in the bores, which would indicate a head gasket or other sealing issue requiring additional service.
   ⚠Do not allow debris to fall into the cylinder. Use compressed air to clean bores carefully or stuff clean rags in openings
8. 8

   Prepare new glow plugs
   Remove new glow plugs from packaging and verify correct part numbers for the 6.7L Cummins application. Apply a thin coat of anti-seize compound to the threads only, keeping anti-seize away from the tip and electrical terminal. Do not over-apply as excess can cause torque value errors.
   ℹ️Never apply anti-seize to the glow plug tip or terminal area. Apply only to the threaded portion
9. 9

   Install new glow plugs
   Thread each new glow plug into its cylinder head bore by hand until finger-tight. Ensure each plug threads smoothly without cross-threading. Once all plugs are hand-tight, use a torque wrench to tighten each glow plug to specification. Note: The torque specification listed is for spark plugs and may not apply to diesel glow plugs. Consult manufacturer specifications for exact glow plug torque (typically 10-15 Nm for this engine).
   ⚠️Over-torquing glow plugs can damage cylinder head threads. Under-torquing can cause combustion gas leakage. Use proper torque specification
10. 10

    Reconnect electrical system
    Apply a small amount of dielectric grease to each glow plug terminal. Install new O-rings on electrical connectors if originals show wear. Reconnect each electrical connector to its corresponding glow plug, ensuring a positive click when seated. Route the wiring harness as originally configured and secure with clips.
    Torque spec

    Ignition Coil Bolt15 Nm (11 lb-ft)
11. 11

    Reinstall engine cover
    Position the engine cover over the engine bay, aligning the mounting points with the clips on the engine. Press down firmly at each clip location until the cover seats completely. Verify all clips have engaged properly by attempting to lift the cover at each corner.
    Torque spec

    Engine Cover Clips4 Nm (3 lb-ft)

Reassembly

1. Reconnect both negative battery cables to restore power
2. Do not start engine immediately; allow glow plug system to initialize
3. Clear any diagnostic trouble codes related to glow plug system using scan tool if available

Verification

• Turn ignition to ON position without starting and verify glow plug indicator light functions normally (illuminates briefly then extinguishes)
• Start engine and observe for normal cold start behavior without excessive cranking
• Monitor for white smoke or rough idle during warm-up; should clear within 30-60 seconds
• Use scan tool to verify no glow plug system fault codes are present
• After engine reaches operating temperature, verify smooth idle and no misfires
• Test cold start performance on next cold engine start to confirm proper glow plug operation

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