Cummins/Onan 12.5RDJC-53CR Generator Set

Tools: Feeler gauge

1. Locate switch on the gear cover on the side of the engine above the oil filter.
2. Loosen the stationary contact.
3. Adjust the point gap to .020 inch.
4. Replace burned or faulty points.

⚠ Adjust only when plant is stopped.

1. Adjust only when plant is stopped.
2. Move the adjustable resistor slide tap until the charging rate is approximately 2 amperes.
3. For frequent starts, move slide tap nearer the ungrounded lead to increase charging rate slightly.
4. Avoid overcharging.

1. Loosen the nut on the belt tightener pulley shaft.
2. Move the shaft left or right in the elongated slot in the pulley mounting bracket until a deflection of 1/2-inch is obtained.
3. Deflection measured with about 15 pounds of force at a point midway between fan pulley and belt tightener pulley.
4. Tighten nut securely.

⚠ If the governor is too sensitive a rapid hunting condition occurs (alternate increasing and decreasing speed).

1. Turn the sensitivity adjusting ratchet accessible through a covered access hole on the side of the blower housing.
2. Radiator cooled: clockwise gives more sensitivity when full load is applied; counterclockwise gives less.
3. City water cooled: counterclockwise gives more sensitivity; clockwise gives less.
4. Adjust for maximum sensitivity without hunting, then readjust speed.
5. Replace the knockout plug in the blower housing and secure the speed stud lock nut.

Tools: Tachometer

1. Change spring tension by turning the governor spring nut.
2. Turn the nut clockwise (more spring tension) to increase RPM.
3. Turn counterclockwise to reduce governed speed.
4. Hold a tachometer against the flywheel cap screw.

⚠ Battery polarity must agree with the rectifier located in the control box. If battery ground must be changed, reverse the rectifier connection.

1. Connect battery positive (+) to starter engaging solenoid terminal post.
2. Connect battery negative (-) to a good ground on the engine.
3. Battery is connected for negative (-) ground.
4. For 24 volt cranking, provide two 12 volt batteries connected in series (one battery negative to the other battery positive).

⚠ Crank engine one revolution if the camshaft pump lobe is up, to permit hand priming.

1. Disconnect the fuel return line.
2. Operate the hand priming lever on diaphragm type fuel transfer pump until no air bubbles in fuel flow from the return line fitting.
3. Connect the fuel return line.
4. Return priming lever to lowest (disengaged) position to permit normal pump operation.

⚠ After running unit 10 minutes the closed cooling system is pressurized and hot. Open the 14 pound pressure cap slowly to vent pressure.

1. Remove fill cap.
2. Open fill vent valve (turn counterclockwise).
3. Remove vent plug.
4. Fill with coolant until vents begin to overflow.
5. Close fill vent valve (turn clockwise).
6. Replace vent plug and fill cap.
7. Operate unit 10 minutes at full load and watch for leaks.
8. Shut down unit; slowly open pressure cap, check level, fill system to top with coolant.

1. Place pan under old filter and remove by screwing counterclockwise.
2. Clean filter mounting area.
3. Install new filter, oil filter gasket and screw filter on clockwise until gasket touches mounting base.
4. Tighten 1/2 turn.

⚠ Discharged batteries are subject to severe damage if exposed to freezing temperatures. Store all batteries fully charged.

Tools: Trickle charger

1. Run set until thoroughly warm; generator under at least 50 percent load.
2. Shut down engine and drain oil base while still warm; refill and attach a warning tag indicating viscosity of oil used.
3. Disconnect batteries and remove from vessel; maintain liquid level and use a trickle charger.
4. Provide a suitable cover for the entire unit.

⚠ Continuous running under one half load during the first few hundred hours usually results in poor piston ring seating, causing higher than normal oil consumption and blowby.

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 the crankcase oil after 50 hours of operation; drain while the engine is still hot.

⚠ Do not smoke while servicing batteries. Explosive gases are emitted from batteries in operation.

Tools: Hydrometer

1. Remove cover and all protective wrapping; remove plug from exhaust outlet.
2. Check warning tag on oil base and verify oil viscosity is correct for ambient temperature.
3. Clean and check battery; measure specific gravity (1.260 at 77 F [25 C]) and verify level at split ring.
4. Check that fuel lines and fittings are secure, without leaks.
5. Service cooling system with clean fresh water; prime water pump and bleed all air.
6. Connect batteries and verify no loads are connected to generator.
7. Start engine.
8. Check all gauges; unit is ready for service.