Cummins/Onan 20W-20 Generator Set

⚠ Do not adjust pressure without a testing fixture.

Tools: Diesel Nozzle Tester 420-0184

1. Remove nozzle from the engine.
2. Remove plug from center of cap nut and loosen cap nut.
3. Install nozzle on a static fuel nozzle testing fixture.
4. Adjust opening pressure to 1750 psi by turning adjusting screw.
5. Clockwise increases pressure, counterclockwise decreases it.

⚠ Four-cylinder engines do not have a BC mark on the flywheel.

Tools: Feeler gauge

1. Rotate flywheel clockwise until No.1 cylinder is on compression stroke at TC mark.
2. Turn 10-45 degrees past TC.
3. Check clearance between rocker arm and valve with feeler gauge.
4. Adjust with lock nut securing rocker arm.
5. Turn flywheel 180 degrees for No.2, then No.4, then No.3 cylinder, adjusting each.

Tools: Thermometer

1. Remove thermostat from cylinder head.
2. Heat a pan of water to approximately 150 F.
3. Suspend thermostat in water; it should start to open.
4. Remove from hot water and allow to cool; it should close in a short time.
5. Replace if it sticks or does not operate properly.
6. Always install a new gasket when replacing the thermostat.

Tools: Flushing gun

1. Drain radiator, cylinder block and exhaust manifold.
2. Remove inlet and outlet hoses between engine and radiator.
3. Close all drain plugs; attach flushing gun nozzle to water outlet.
4. Restrict inlet opening until system fills with water, then apply air pressure gradually.
5. Repeat until water from cylinder block flows clean.
6. Remove flushing gun.
7. Reinstall thermostats, hoses and drain plugs; refill with proper coolant.
8. Check system for leaks.

Tools: Filter wrench

1. Place pan under old filter and remove by turning counterclockwise.
2. Clean filter mounting area.
3. Lubricate gasket on new filter with oil.
4. Screw filter on clockwise until gasket touches mounting base.
5. Tighten 1/2 turn.

⚠ Starter cranking is too fast; oil or inhibitor fluid will fire if cranked with starter.

1. Run engine until thoroughly warm under at least 50 percent load.
2. Shut down and drain oil base while warm; refill.
3. Remove glow plugs, pour 1 ounce rust inhibitor into each cylinder, install glow plugs.
4. Crank engine by hand only to distribute oil.
5. Service air cleaner per Maintenance Schedule.
6. Clean throttle and governor linkage; wrap with clean cloth.
7. Plug exhaust outlets.
8. Disconnect battery and follow standard storage procedure.

⚠ Do not smoke while servicing batteries.

1. Remove cover and protective wrapping; remove plug from exhaust outlet.
2. Check warning tag on oil base and verify oil viscosity.
3. Clean and check battery; measure specific gravity.
4. Check fuel injectors and fuel lines are secure and correctly torqued.
5. Clean radiator.
6. Connect batteries.
7. Verify no loads are connected to engine.
8. Start engine.

⚠ Return priming lever inward (disengaged position) to permit normal pump operation.

1. Disconnect fuel return line.
2. Operate hand priming lever on fuel transfer pump.
3. Continue until fuel flowing from return line is free of air bubbles.
4. Reconnect the fuel return line.
5. If camshaft pump lobe is up, crank engine one revolution to permit hand priming.

⚠ Continuous running under one half load during first few hundred hours may cause poor ring seating.

1. Run one half hour at 1/2 load.
2. Run one half hour at 3/4 load.
3. Run at full load.
4. Drain and replace crankcase oil after first 50 hours; drain while still hot.

⚠ Do not exceed the one minute preheat periods.

⚠ Do not use ether as a cold weather starting aid.

1. Engage PREHEAT switch 30 seconds if above 55 F, 60 seconds if below 55 F.
2. Engage START switch while continuing preheat.
3. Hold until engine comes up to speed.
4. If engine fails to start in 15-20 seconds, repeat preheat and start.
5. Verify oil pressure gauge reads at least 20 psi.

1. Push fuel solenoid switch to stop position.
2. Release switch when set stops.
3. If stop circuit fails, close fuel valve.

⚠ Do not pry the cover and body apart; this would damage the diaphragm.

Tools: Screwdriver, File

1. Remove pump inlet and outlet lines.
2. Remove two cap screws holding pump to engine and lift off.
3. Notch cover and body with a file; remove six screws.
4. Tap body with a screwdriver to separate the two parts.
5. Drive out rocker arm hinge pin.
6. Remove rocker arm, spring and link.
7. Lift out diaphragm assembly and diaphragm spring.