Cummins/Onan HGJAC Generator Set

⚠ Voltage/frequency-sensitive equipment may be damaged by power line frequency variations; disconnect them before adjustments.

Tools: Variable load bank up to 7 kW, Frequency meter (within 0.3%), Voltmeter (within 0.5%), AC ammeter

1. Warm up the genset for at least 5 minutes at 1/2 to 3/4 rated load with the choke fully open.
2. Adjust frequency close to the Table 8-3 value with the speed adjusting nut.
3. With the engine warm, remove all loads and adjust the idle stop screw to 51-53 Hz (60 Hz genset) or 41-43 Hz (50 Hz genset).
4. Let the throttle lever go and recheck/adjust No-Load frequency to Table 8-3; bump the governor arm to check stabilization.
5. Connect rated load; if droop is out of spec move the governor spring hook one or two notches and recheck.
6. Confirm the governor does not hunt under the loading sequence.

⚠ Voltage/frequency-sensitive equipment may be damaged; disconnect before adjusting

Tools: load bank, frequency meter, voltmeter

1. Warm up genset five minutes at 1/2 to 3/4 rated load.
2. Adjust frequency to Table 8-4 value with speed adjusting nut.
3. With engine warm and no loads, set idle stop screw to 51-53 Hz (60 Hz).
4. Recheck no-load frequency and bump governor arm for stability.
5. Connect rated load; move governor spring hook to correct droop.
6. Check for hunting under the specified load sequence.

Tools: Socket wrench, Feeler gauge, Torque wrench

1. Adjust when the engine is at room temperature.
2. Remove the spark plugs so the engine is easier to turn over.
3. Use a socket wrench on the generator pulley nut to turn the engine clockwise; remove the snap-in cover.
4. Remove the valve covers with rags in place to catch oil.
5. Turn engine until No. 2 intake valve is at max lift; adjust No. 1 intake valve lash.
6. Turn engine until No. 2 exhaust valve is at max lift; adjust No. 1 exhaust valve lash.
7. Turn engine until No. 1 intake valve is at max lift; adjust No. 2 intake valve lash.
8. Turn engine until No. 1 exhaust valve is at max lift; adjust No. 2 exhaust valve lash.
9. Secure valve covers using new gaskets and torque cover screws to 5.5 lb-ft (8 N-m).
10. Replace the spark plugs and pulley nut cover.

⚠ If fault shutdown or STOP pressed during voltage set mode, adjustment is not stored

Tools: AC voltmeter, Frequency meter

1. Disconnect all alternator loads.
2. Connect accurate AC voltmeter and frequency meter.
3. Start genset and let voltage/frequency stabilize 5-10 seconds.
4. Rapidly press control switch to START 6 times within 1 minute.
5. Press START briefly to raise voltage ~0.6 V per press.
6. Press START for ~2 seconds to lower voltage ~0.6 V per press.
7. Normal operation resumes 20 seconds after last adjustment.

⚠ Adjusting engine speed above equipment manufacturer's specification could cause equipment to operate at speeds in violation of Federal and State Standards for Safety.

⚠ Moving parts can cause severe personal injury or death. Take care when measuring engine speed with tachometer. Must be qualified mechanic.

Tools: Accurate tachometer

1. Adjust only by qualified mechanic using accurate tachometer.
2. Set low-idle and high-idle speeds to values in equipment Operator's Manual. If absent, adjust low-idle to 1400 RPM and high-idle to 3400 RPM.
3. Start engine and move throttle lever to lowest speed position.
4. Adjust low-idle speed stop screw on carburetor to obtain specified low-idle speed.
5. For cable controlled engines: move throttle lever to highest speed position. Loosen high-idle speed stop plate clamping screw and rotate stop plate while holding throttle control arm against it until
6. For lever controlled engines: adjust lever stop screw while holding throttle lever against it until specified high-idle speed is obtained.
7. Check for full, smooth movement of throttle control arm between stop positions.

⚠ Operating at low altitude with a high altitude setting can cause power loss, overheating and engine damage.

1. Reset the carburetor for the current altitude using the altitude adjust knob.
2. For best fuel economy and genset operation, always reset when returning to lower altitudes.

⚠ Accidental starting can cause severe injury or death. Always disconnect spark plug and battery before resetting engine control cables.

1. Stop engine and disconnect spark plug and battery (negative cable).
2. Push choke knob in to full open-choke position and throttle lever to lowest speed position.
3. Loosen cable clamp at engine bracket if necessary and hook cable wires into hook holes in choke and throttle control arms.
4. Rotate choke and throttle control arms clockwise, hold against stops, pull slack out of cables and tighten cable clamp.
5. Check for smooth movement and full travel of choke knob and throttle lever. Remove air cleaner element to see choke plate opens and closes fully. Check throttle control arm touches stop plate and thro
6. Reassemble air cleaner and reconnect spark plug and battery.

Tools: Battery terminal puller, Torque wrench

1. Loosen the governor shaft nut by turning it clockwise and remove the arm.
2. Use a battery terminal puller to break the taper fit of the shaft in the arm hub.
3. Reattach arm and hub making sure the pins and holes engage; thread the shaft nut on counterclockwise.
4. Check free rotation of the arm and let the governor spring take up all play; linkage must push throttle against the wide open throttle stop.
5. Torque the shaft nut to 8 lb-ft (11 N-m) counterclockwise.
6. Push the governor arm down and check for binding or interference.

Tools: Feeler gauge, Torque wrench

1. Bar the engine until the lands on the flywheel directly face the coils.
2. Place a 0.012 inch (0.03 mm) thick feeler gauge between the coil and the land.
3. Hold the coil tight against the feeler gauge and land and torque the two mounting bolts to 5 lb-ft (7 N-m).

Tools: feeler gauge, torque wrench

1. Bar the engine until the flywheel lands directly face the coils.
2. Place a 0.012 inch (0.3 mm) feeler gauge between coil and land.
3. Hold coil tight against gauge and land.
4. Torque the two mounting bolts to 5 lb-ft (7 N-m).

⚠ Adjust valve lash only when engine is at room temperature

Tools: Feeler gauge, Socket wrench, Torque wrench

1. Adjust valve lash with engine at room temperature.
2. Remove spark plugs and valve covers.
3. Turn engine until No. 2 intake valve is at maximum lift.
4. Adjust No. 1 intake valve lash to 0.004 in (0.10 mm).
5. Turn engine until No. 2 exhaust valve at maximum lift; adjust No. 1 exhaust.
6. Turn engine until No. 1 intake valve at maximum lift; adjust No. 2 intake.
7. Turn engine until No. 1 exhaust at maximum lift; adjust No. 2 exhaust.
8. Torque lock nuts to 6.5 lb-ft (8.5 Nm) and install valve covers.

⚠ Hazardous voltage: touching uninsulated live parts can cause severe injury or death

Tools: AC voltmeter, frequency meter

1. Disconnect all generator loads and connect accurate AC volt and frequency meters.
2. Start genset; let voltage and frequency stabilize 5 to 10 seconds.
3. Rapidly press control switch to START 6 times within 1 minute of start.
4. Adjust up: press START and release quickly (voltage rises about 0.6 volt).
5. Adjust down: press START and release after about 2 seconds (voltage drops about 0.6 volt).