Cummins/Onan P9500df Generator Set

⚠ Must be done when engine is cold

Tools: feeler gauge

1. Remove rocker arm cover and carefully remove gasket, replace if torn or damaged
2. Remove spark plug so engine can be rotated more easily
3. Rotate engine to top dead center (TDC) of compression stroke
4. Confirm both rocker arms are loose at TDC on compression stroke; if not, rotate engine 360 degrees
5. Insert feeler gauge between rocker arm and push rod to check clearance
6. If adjustment required, hold adjusting nut and loosen jam nut
7. Turn adjusting nut to obtain correct valve lash
8. Hold adjusting nut and tighten jam nut to 106 in-lb (12 N.m)
9. Recheck valve lash after tightening jam nut
10. Perform for both intake and exhaust valves
11. Install rocker arm cover, gasket and spark plug

⚠ Never dispose of used oil into sewer, ground, or waterways

Tools: oil pan

1. Operate or maintain generator on flat surface
2. Stop engine
3. Let engine cool for several minutes
4. Place oil pan under oil drain plug
5. Clean around oil drain plug with damp rag
6. Remove oil drain plug
7. Allow oil to completely drain
8. Replace oil drain plug
9. Fill crankcase with oil per Adding Engine Oil procedure

⚠ Internal pressure can build in crankcase while running; allow oil to cool before removing dipstick

1. Operate or maintain generator on flat surface
2. Stop engine if running
3. Let engine cool for several minutes
4. Clean around oil fill plug/dipstick with damp rag
5. Remove oil fill plug/dipstick
6. Thread dipstick all the way back in, remove and check oil level between H and L lines

⚠ Never use gasoline or flammable solvents to clean air filter

1. Turn off generator and let cool for several minutes
2. Move generator to flat, level surface
3. Unclip clips on top and bottom of air filter cover
4. Remove black coarse air filters
5. Wash foam air filter elements in household detergent soap and warm water, slowly squeeze to clean
6. Rinse in clean water with slow squeezing action
7. Dispose of used soap solution properly
8. Dry air filter elements with slow firm squeezing action
9. Coat dry air filters with clean engine oil
10. Squeeze filters to remove excess oil
11. Install filters back into unit: gray (fine) filter first, then black (coarse) filter outside
12. Install air filter cover and secure assembly

⚠ Check and clean after every 100 hours of use or 6 months

Tools: wire brush

1. Generator must be cold to perform this maintenance
2. Move to flat, level surface
3. Remove 6 screws holding muffler cover in place
4. Locate screw on tip of muffler, remove, pull spark arrestor out
5. Replace spark arrestor screen if torn/ripped (only use Cummins spark arrestors)
6. If not torn, clean using wire brush, commercial solvent, or compressed air
7. Install spark arrestor back into muffler, fully pushed in tight on tip
8. Replace muffler cover and tighten all 6 screws

Tools: fuel pan

1. Make sure generator is off and away from open flames
2. Place pan under carburetor assembly
3. Loosen screw at bottom of bowl and allow gas to drain out
4. After all gas has drained, tighten screw

⚠ Never apply side load when removing spark plug

Tools: 13/16" spark plug socket wrench

1. Stop generator and let cool for several minutes
2. Move generator to flat, level surface
3. Remove spark plug boot by pulling directly away from engine
4. Clean area around spark plug
5. Remove spark plug using 13/16" spark plug socket wrench
6. Place clean rag over opening to prevent dirt entering combustion chamber
7. Inspect spark plug for cracked/chipped insulator, excessive wear, gap (0.027-0.032 in.)
8. Hand-thread spark plug back in until it bottoms out, then turn with wrench to fully seat
9. Replace spark plug boot, ensuring full engagement

⚠ Gasoline stored for as little as 60 days can go bad

1. Switch Engine Switch to STOP so generator does not draw power from battery
2. Clean the generator
3. Drain all gasoline from fuel tank as best as possible
4. With fuel shut off valve open, start engine and run until remaining gasoline in lines/carburetor is consumed and engine shuts off
5. Close fuel shut off valve
6. Drain remaining gas in carburetor float bowl
7. Change the oil
8. Remove spark plug, place about 1 tablespoon of oil in spark plug opening, pull recoil handle several times to distribute oil
9. Replace spark plug
10. Move generator to a clean, dry place for storage

1. Remove spark plug wire from spark plug
2. Loosen and remove bolt on battery hold-down plate, swing plate out
3. Tip battery forward slightly to access battery cables
4. Disconnect black negative cable first
5. Disconnect red positive cable second and remove battery
6. Install new battery into generator frame
7. Connect red positive cable to battery first
8. Connect black negative cable to battery second
9. Install battery hold-down plate using nuts removed earlier
10. Install spark plug wire onto spark plug