Full Engine Tune-Up

Complete maintenance service for the 5.9L Cummins diesel engine including fuel filter replacement, valve adjustment, air filter service, and fluid checks. Note: Diesel engines do not have spark plugs or ignition coils.

Warnings

Tools required

Parts

• Fuel filter/water separator (primary) × 1 — Mopar 68157291AA or equivalent
• Fuel filter (secondary/lift pump) × 1 — Use OEM specification
• Valve cover gasket × 1 — Use OEM specification
• Air filter element × 1 — Use OEM specification
• Crankcase breather filter × 1 — Use OEM specification
• Engine oil × 12 — 15W-40 diesel rated
• Oil filter × 1 — Use OEM specification

Fluids

• 15W-40 diesel engine oil — 12 qt

Preparation

1. Park vehicle on level surface and engage parking brake
2. Allow engine to cool completely (minimum 3 hours after operation)
3. Disconnect negative battery cable
4. Gather all tools, parts, and fluids before beginning
5. Place drain pan under fuel filter housing to catch diesel fuel spillage

Procedure

1. 1

   Replace air filter and breather
   Open air filter housing by releasing spring clips. Remove and inspect old air filter element for excessive dirt or oil contamination. Install new air filter element ensuring proper seating. Replace crankcase breather filter located in air intake tube. Secure housing with clips.
2. 2

   Drain engine oil
   Position drain pan under oil pan drain plug. Remove drain plug and allow oil to drain completely (approximately 12 quarts). Inspect drain plug threads and washer, replace washer if damaged. Reinstall drain plug hand-tight, then torque to specification per service manual (not provided in torque list).
3. 3

   Replace oil filter
   Move drain pan under oil filter located on the engine block (verify side per your model year; typically passenger side on the 5.9L Cummins). Use oil filter wrench to remove old filter. Clean filter mounting surface on engine block. Apply thin film of clean engine oil to gasket of new filter. Install new filter hand-tight, then turn an additional 3/4 turn.
4. 4

   Replace fuel filters
   Locate primary fuel filter/water separator on driver side frame rail. Place drain pan underneath. Open drain valve at bottom of filter housing to drain water and fuel. Use fuel filter wrench to remove filter canister. Clean sealing surfaces. Install new filter with fresh diesel fuel in canister to aid priming. Hand-tighten filter until gasket contacts, then turn an additional 1/2 turn. Close drain valve. Repeat process for the secondary fuel filter if equipped (location and configuration vary by model year and fuel system generation; verify per service manual).
5. 5

   Remove valve cover
   Disconnect any breather hoses or electrical connections from valve cover. Remove valve cover bolts in reverse of tightening sequence (outside to inside pattern). Carefully lift valve cover from cylinder head. Remove old gasket material from both valve cover and cylinder head mating surfaces using gasket scraper. Clean surfaces thoroughly with shop towels.
6. 6

   Rotate engine to TDC cylinder #1
   Using breaker bar on crankshaft pulley bolt, rotate engine clockwise until timing mark on crankshaft pulley aligns with TDC indicator on timing case. Verify cylinder #1 is on compression stroke by confirming both intake and exhaust rocker arms on cylinder #1 have clearance (not compressed). If not, rotate engine one complete additional revolution.
7. 7

   Check and adjust valve lash - Set 1
   With engine at TDC compression for cylinder #1, adjust the specific valves that are on the base circle per the service manual procedure (based on firing order 1-5-3-6-2-4), not a simple front/rear cylinder grouping. Verify intake and exhaust valve lash specifications against the year-specific service manual (commonly ~0.010" intake / ~0.020" exhaust for 12-valve; confirm for 24-valve engines). Insert appropriate feeler gauge between rocker arm and valve crosshead. Loosen locknut on adjusting screw, turn screw until slight drag is felt on feeler gauge, hold screw and tighten locknut. Recheck clearance after tightening. Repeat for all six valves on these three cylinders.
8. 8

   Rotate engine 360 degrees
   Rotate engine clockwise exactly one complete revolution (360 degrees) until the timing mark returns to TDC. This positions the remaining valves (per firing order 1-5-3-6-2-4) for adjustment.
9. 9

   Check and adjust valve lash - Set 2
   With engine rotated 360 degrees from the previous position, adjust the remaining valves per the service manual procedure (based on firing order 1-5-3-6-2-4). Follow same procedure as step 7: intake valves 0.010", exhaust valves 0.020". Use feeler gauges to verify proper clearance, adjust as needed, and verify after tightening locknuts.
10. 10

    Install valve cover with new gasket
    Position new valve cover gasket on cylinder head. Ensure gasket is properly seated in groove. Carefully lower valve cover onto gasket without shifting gasket position. Install valve cover bolts finger-tight. Tighten bolts in sequence from center outward in a crisscross pattern to specified torque.
    Torque spec

    Valve Cover Bolts10 Nm (7 lb-ft)
11. 11

    Refill engine oil
    Remove oil fill cap on valve cover. Using funnel, add 11 quarts of 15W-40 diesel engine oil. Start with 11 quarts, then check dipstick. Add remaining oil in small increments until dipstick reads full mark. Do not overfill. Install oil fill cap.
12. 12

    Prime fuel system
    Prime the fuel system per the correct method for your model year: operate the manual primer pump handle until firm resistance is felt (mechanical systems), or use the electric lift pump/key-cycle priming procedure (common-rail systems). Verify per service manual. This is critical after fuel filter replacement to prevent hard starting or air-locked injection pump.
13. 13

    Reconnect and perform initial start
    Reconnect negative battery cable. Reconnect any electrical connections or hoses to valve cover. Turn ignition to run position for 30 seconds to allow lift pump to prime (do not crank). Start engine and check immediately for oil pressure indication. Check for fuel leaks at filter housings. Check for oil leaks at valve cover gasket and oil filter.

Reassembly

1. Verify all electrical connections and breather hoses are properly reconnected to valve cover
2. Ensure no tools or rags are left in engine compartment
3. Verify oil fill cap and dipstick are properly installed
4. Check that all drain valves on fuel filters are closed
5. Dispose of used oil and fuel filters according to local environmental regulations

Verification

• Start engine and verify smooth idle with no unusual noises or valve train clatter
• Verify oil pressure is within normal range (10-30 psi at idle when warm)
• Verify no oil leaks at valve cover gasket, oil filter, or drain plug
• Verify no fuel leaks at filter housings or connections
• Check engine oil level after engine has run for 5 minutes and been shut off for 5 minutes - should be at full mark on dipstick
• Verify fuel filter housing drain valve is showing clean fuel with no water
• Test drive vehicle to verify proper engine performance and smooth operation through all RPM ranges

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