Cummins/Onan 350NTTA2 Generator Set

Tools: Frequency meter or tachometer

1. Idle Speed potentiometer: turn counterclockwise 20 turns, then clockwise 10 turns (mid position).
2. Run Speed potentiometer: turn counterclockwise 20 turns, then clockwise 10 turns (mid position).
3. Gain potentiometer: turn screw fully counterclockwise.
4. Droop potentiometer: fully counterclockwise for isochronous, approx. 40 for 3 percent droop, approx. 80 for 5 percent droop.

Tools: Frequency meter or tachometer

1. Close main line circuit breaker and apply approximately 1/4 of rated load.
2. Make sure engine speed is constant.
3. Turn Gain potentiometer clockwise slowly until engine speed is not constant.
4. Slowly turn potentiometer counterclockwise until constant speed is achieved.
5. Turn potentiometer counterclockwise an additional 1/2 division.

⚠ Do not adjust any other voltage regulator potentiometers or rheostats; they are factory-calibrated.

Tools: Screwdriver

1. Loosen voltage control rheostat locking nut; turn rheostat fully counterclockwise, fully clockwise, then to mid position.
2. Remove cover from voltage regulator housing on engine side of generator conduit box.
3. With set operating and voltage monitored, adjust Coarse Voltage Potentiometer to desired generator voltage.
4. Perform fine voltage adjustment (+3 percent) with control rheostat and retighten locking nut.
5. Stop and restart generator set to confirm proper operation.
6. If voltage cannot be brought within range, check wiring per unit wiring diagram and repeat; contact service representative.
7. Shut down set and replace voltage regulator housing cover before returning to service.

⚠ Contact with hot coolant can result in severe burns. Allow system to cool before removing filters.

1. Close the shutoff valves.
2. Unscrew the coolant filter and discard.
3. Apply a light coat of lubricating oil to the gasket surface.
4. Install new filter, tighten by hand until seal touches filter head, then one-half to three-fourths turn more.
5. Open the shutoff valves.

⚠ Allow cooling system to cool before releasing pressure and removing radiator cap.

1. Disconnect coolant heater from AC power; remove radiator/expansion tank cap.
2. Open draincock, disconnect lower radiator hose or remove heat exchanger drain plug.
3. Remove pipe plug from water pump body; open cylinder block and oil cooler draincocks; drain completely.
4. Close block and oil cooler draincocks; replace water pump pipe plug.
5. Close draincock and reconnect hose or replace drain plug.
6. Fill with clean water, leave cap off, operate engine 5 minutes above 194 F (90 C).
7. Shut off engine and drain; repeat until flush water is clean.
8. Drain completely, then fill cooling system with proper coolant.

Tools: Compressed air

1. Remove wing nut, flat washer and rubber washer holding cover; lift cover away from filter assembly.
2. Lift out breather element, vapor element and gasket.
3. Clean all parts with approved solvent; dry with compressed air 30 psi (207 kPa).
4. Inspect all parts, replace if necessary.
5. Reassemble filter assembly, replace cover and secure.

⚠ Do not permit any flame, lit cigarette, spark, pilot light or arcing equipment near the fuel system.

1. Remove the fuel filters and discard.
2. Fill the new filters with diesel fuel and coat the sealing gasket lightly with fuel.
3. Install and tighten by hand until gasket just touches the filter head.
4. Tighten an additional one-half to three-fourths of a turn.

⚠ Handle filters with care to prevent damage; install recommended replacement part if damaged.

Tools: Compressed air

1. Loosen fastener(s) and remove air cleaner housing end cap.
2. Remove air filter element from filter housing.
3. Blow low pressure compressed air 30 psi (207 kPa) through element from the clean side, nozzle at least 1 inch (25 mm) away.
4. Soak filter at least 15 minutes in water and Donaldsons D1400 solvent.
5. Rinse with clean low pressure water and air dry; do not blow dry. Reinstall when dry; replace after two cleanings.

⚠ Crankcase pressure can blow out hot oil; do not check oil while generator set is operating.

Tools: Waste container, Torque wrench

1. Warm engine to operating temperature, shut down, place Automatic Start switch OFF and disconnect negative battery cable.
2. Remove oil drain plug or open drain valve; collect oil; replace plug; torque to 60-70 ft-lb (81-95 N.m).
3. Unscrew oil filter and discard.
4. Coat new filter gasket with oil and fill filter with clean new oil.
5. Install filter, tighten 2/3 turn by hand after seal touches bracket. Do not overtighten.
6. Fill crankcase to high mark of dipstick.
7. Reconnect negative battery cable, start engine, check for oil leaks.
8. Shut off engine, wait 15 minutes, check oil level and add oil if required.

1. Remove each fuel filter and fill with clean fuel.
2. Put a light coat of fuel on the sealing gasket.
3. Install and tighten by hand until gasket just touches the filter head.
4. Tighten the filter an additional one-half to three-fourths of a turn.

Tools: Priming pump with pressure gauge, Torque wrench

1. Remove oil inlet line from turbocharger housing, fill bearing housing with clean lubricating oil, replace and secure line.
2. Fill crankcase to L (low) mark on dipstick.
3. Remove plug from oil filter housing head and connect hand or motor-driven priming pump with pressure gauge.
4. Prime until 30 psi (207 kPa) pressure is obtained.
5. Disconnect fuel solenoid valve wire; depress Crank switch while maintaining 15 psi (103 kPa) oil priming pressure for 15 seconds.
6. Stop cranking, remove priming equipment, replace plug; torque to 15 to 20 ft lb (20 to 27 N.m).
7. Reconnect fuel shutoff valve wire; complete oil fill to H (high) mark on dipstick.

1. Loosen the strap fastening the air intake elbow to the air cleaner housing.
2. Disconnect intake elbow by moving it straight away from the air cleaner.
3. Remove air cleaner from mounting plate and discard.
4. Reassemble a new air cleaner to mounting plate; secure fasteners.
5. Reassemble air intake elbow to air cleaner housing; secure mounting strap.