Cummins/Onan 550 (625) Engine

⚠ To get maximum brake operating efficiency and to prevent engine damage, follow instructions in this section.

Tools: 3163530 Brake Feeler Gauge - 7.00 mm [0.276 in]

1. Remove eight capscrews, isolator assemblies, rocker lever cover, and rocker lever cover gasket.
2. Locate engine brake set marks: BRAKE SET 1-6, 2-5, 3-4.
3. Rotate engine clockwise until set mark aligns with stamped mark on front gear cover.
4. Verify both intake and exhaust valves on cylinder are closed and camshaft follower is on inner base circle.
5. Press engine brake lever down to verify follower contacts camshaft.
6. Loosen locknut on brake lever adjusting screw and back out one turn.
7. Insert feeler gauge Part No. 3163530 between bottom of engine brake piston and top of exhaust valve pin.
8. Tighten adjusting screw until drag on feeler gauge is felt.
9. Hold adjusting screw and tighten locknut to 20 Nm [15 ft-lb]. Remove feeler gauge.
10. Repeat on remaining cylinders.
11. Install rocker lever cover gasket, cover, isolators, and capscrews. Tighten to 25 Nm [18 ft-lb].

⚠ Do not use fan blade to bar over the engine; that can damage blades and cause property damage and personal injury.

Tools: Ohmmeter

1. Measure the resistance of the MPU; replace if not between 1,000 ohms and 1,050 ohms.
2. With the MPU removed, bar the engine until a flywheel gear tooth lines up in the center of the mounting hole.
3. Thread the sensor in gently by hand until it just touches the gear tooth.
4. Back it out 1/4 turn and set the locknut.
5. After adjustment, verify output voltage of the MPU is correct.

⚠ Do not use solvent to clean rocker cover gasket.

⚠ Batteries can emit explosive gases. Disconnect battery before service.

Tools: 3375044 Torque Wrench, Feeler gauge

1. Disconnect battery.
2. Locate valve set marks on outside of vibration damper: A adjusts cylinders 1 or 6, B adjusts cylinders 2 or 5, C adjusts cylinders 3 or 4.
3. Rotate engine clockwise to align set mark with pointer. Check both valves are closed.
4. Loosen injector adjusting screw locknut. Use dial-type torque wrench to tighten injector rocker lever adjusting screw.
5. Back out adjusting screw one or two turns. Tighten injector adjusting screw to 8 Nm [70 in-lb].
6. Hold injector lever adjusting screw and tighten locknut to 75 Nm [55 ft-lb].
7. Set valves on same cylinder using feeler gauge: intake 0.36 mm [0.014 in], exhaust 0.69 mm [0.027 in].
8. Tighten valve adjusting screw to 0.6 Nm [5 in-lb]. Hold screw and tighten locknut to 45 Nm [33 ft-lb].
9. Repeat for all cylinders following firing order 1-5-3-6-2-4.

⚠ Accidental starting can cause severe personal injury or death; disconnect negative (-) battery cable with insulated wrench.

⚠ Set generator set to off mode before disconnecting/connecting harness connectors.

Tools: True RMS meter, Insulated wrench, Jumper leads

1. Verify power to control: Control Alive indicator should be flashing on base board.
2. Clean battery cable terminals and tighten connections using an insulated wrench.
3. Remove F4 and check continuity; if open, replace with same type/amp rating (5 Amps).
4. If F4 OK, remove connector P7 and check B+ at P7-1 to P7-4 and GND at P7-5 to P7-8.
5. If B+/ground missing, isolate to harness and TB BAT terminal on engine block.
6. If B+ and ground OK, base board may be defective; cycle power by reconnecting P7.
7. Confirm calibration part number matches serial plate; re-enter calibration file if needed.
8. With E-Stop not activated, remove P1 and check continuity between P1-1 (ESTOP-NC1) and P1-2 (ESTOP-NC2).
9. With S12 in Manual, remove P1 and check continuity from P1-6 (MAN) to P1-9 (GND).
10. Remove P3 and check continuity from P3-9 (MAN RUN/STOP) to P3-10 (GND); if none when pressing button, replace front membrane panel.

⚠ Do not remove pressure cap from a hot engine; wait until coolant is below 50C [120F].

Tools: CC2602 Coolant Test Kit

1. Ensure coolant sample is between 10 and 54 C [50-130F].
2. Compare test strip pads to color chart in daylight or cool white fluorescent lighting.
3. Use one strip at a time; do not touch pads.
4. If concentration is below 1.2 units per gallon, replace filter and precharge with liquid.

Tools: Ohmmeter, Feeler gauge

1. Remove the fuel pump control cover, disconnect the wiring jack, and unscrew the assembly from the top of the day tank.
2. With an ohmmeter, test for electrical continuity (switch closed) between each pair of colored leads while holding the assembly vertical; replace if any switch is open (readings should be zero).
3. Lift each float to 1/8 inch (3 mm) below the C-clip stop above it (use a feeler gauge); test for continuity; replace if any switch does not open (readings should be infinity).
4. Use pipe thread sealant when replacing the assembly.

⚠ Accidental starting of the generator set can cause severe personal injury or death. Prevent accidental starting by disconnecting the negative (–) cable from the battery terminal.

⚠ Improper wiring can cause a fire or electrical hazard.

⚠ Backfeed to utility system can cause electrocution or property damage. Do not connect to any building electrical system except through an approved device.

1. Place the control panel run switch in the OFF position.
2. Turn off or remove AC power from the battery charger.
3. Remove the negative (–) battery cable from the set starting battery.
4. Install the transfer switch, select generator output voltage, connect load cables and connect standard/optional AC equipment.

⚠ Ignition of explosive battery gases can cause severe personal injury or death. Always connect negative (–) battery cable last to prevent arcing.

⚠ Ventilate battery area before working on or near battery.

1. Make sure that the PCC is in the OFF mode before connecting the battery cables.
2. Connect the positive battery cable before connecting the negative battery cable to prevent arcing.
3. Service the batteries as necessary.
4. If an automatic transfer switch is installed without a built-in charge circuit, connect a separate battery charger.

⚠ The coolant heater must not be operated while the cooling system is empty or damage to the heater will occur.

1. Connect the heater to a source of power that will be on during the time the engine is not running.
2. Ensure the supply voltage and circuit current is correct for the heater element rating.

1. Ensure the CT dot is facing toward the generator reconnection terminal block (conventional current flowing into the dot).
2. Route the load lead (U, V or W) through the appropriate CT per the Reconnection Diagram.
3. Connect CT secondary wire marked 1 to pin 1 of the CT.
4. Connect CT secondary wire marked 2/3 to pin 3 for low voltage generator sets.

1. The CT has a dot on one side. This dot must face toward the generator (conventional current flowing into the dot).
2. CT21 - U load leads (A phase); CT22 - V load leads (B phase); CT23 - W load leads (C phase).
3. Route the appropriate load wires through each CT.
4. CT secondaries have 3 pins: secondary wire marked 1 to pin 1; wire marked 2/3 to pin 2 for high voltage gensets or pin 3 for low voltage gensets.

⚠ Hazardous voltage! Ensure all power is off before performing control wire installation.

⚠ Always run control circuit wiring in separate metal conduit from AC power cables.

Tools: cable ties, flexible conduit

1. Route the control wiring through the bottom of the control housing, keeping DC wiring away from high voltage AC wiring.
2. Use cable ties to keep control wiring away from sharp edges and AC power cables within the control housing.
3. Use 20 gauge stranded copper wire for digital connections less than 305 metres (1000 feet).
4. Use 18 gauge stranded copper wire for digital connections 305 to 610 metres (1000 to 2000 feet).
5. Determine the gauge of stranded copper wire for relay connections according to the devices attached.