Cummins/Onan GTA8.3 G1 Engine

Tools: 0-30 psi gauge, Pyrometer, Oxygen meter, Timing light

1. Install a 0-30 psi gauge on the intake manifold.
2. Install a pyrometer in the 1/8 inch pipe tapped hole of the exhaust manifold ahead of the turbocharger.
3. Install an oxygen meter exhaust gas pickup in a 1/8 inch pipe tapped hole of the exhaust elbow.
4. With the genset at full load, adjust the power valve for the lowest possible exhaust temperature while observing O2.
5. Turn the power valve closed (toward L) until the engine starts losing RPM.
6. Then turn the power valve open (toward R) until the exhaust temperature reaches the lowest reading.
7. LP vapor only: if O2 cannot be set with the power valve, set power valve to mid-point and use the course adjustment valve.

⚠ DO NOT switch from position 7 to 0, or 0 to 7 while the engine is running.

Tools: Timing light

1. Connect the timing light high tension lead to the No. 1 spark plug (front cylinder).
2. Start the genset.
3. Point the adjustable timing light toward the pointer and TDC mark on the crank pulley.
4. Remove the white plastic cap and turn the timing switch adjustment screw (10 degree range) of the CD1 Ignition Module.
5. Switch position 7 gives the most advanced timing; timing retards 1.4 degrees per switch position toward 0 (full retard).
6. Allow a short delay between each timing position change.
7. Perform the Carburetor Power Valve Adjustment procedure.

⚠ High gas supply pressure can cause gas leaks which can lead to fire and severe personal injury or death.

Tools: Manometers

1. Install the manometers into the two test ports of the gas regulator.
2. Remove the regulator dust cap.
3. Start the genset and run at full load.
4. Turn the adjusting screw until the meter shows the appropriate gas pressure for NG on the mixer side.
5. Turn the screw clockwise to increase pressure.

Tools: Ohmmeter

1. Remove the suppresser.
2. Replace the suppresser if it appears to have overheated.
3. Replace the suppresser if ohmmeter readings indicate less than infinite resistance in both directions.
4. Torque the terminals to 24 in-lbs (2.7 Nm) when reassembling.

⚠ Layers of dust can cause diodes to overheat and fail.

Tools: Ohmmeter

1. Disconnect the diode pigtails from the terminal posts.
2. Measure electrical resistance between each diode pigtail and the plate on which the diode is mounted.
3. Reverse the meter test probes and repeat the tests.
4. Replace the diode if resistance is high or low in both directions.

Tools: Wheatstone bridge or digital ohmmeter

1. Measure winding resistance with a Wheatstone bridge or digital ohmmeter.
2. Replace the stator if winding resistance is not as specified in Table 6-1.
3. Disconnect the exciter stator leads from terminals X and XX.
4. Measure resistance between either lead and the stator laminations.
5. Replace the stator if insulation resistance is less than 1 megohm (1,000,000 ohms).

⚠ Improper installation of CTs will cause a 335 Reverse Power shutdown error (non-parallel units only).

1. Orient the CT dot toward the generator (conventional current flowing into the dot); dot also indicates pin 1.
2. CT21 for U load leads (A phase).
3. CT22 for V load leads (B phase).
4. CT23 for W load leads (C phase).
5. 6 lead generator sets: route generator output leads through the CTs.
6. 12 lead generator sets: route load wires through the CTs.
7. For 12-lead (dual secondary) CTs connect secondary wire 1 to pin 1; wire 2/3 to pin 2 (high voltage) or pin 3 (low voltage).

⚠ Do not use fan blade to bar over engine.

1. Bar the engine until a gear tooth on the flywheel lines up in the center of the mounting hole.
2. Thread the sensor in gently by hand until it just touches the gear tooth.
3. Back it out one quarter turn and set the locknut.

⚠ Electrostatic discharge will damage circuit boards.

⚠ Accidental starting of the generator set while working on it can cause severe personal injury or death.

Tools: Grounding wrist strap

1. Wear a grounding wrist strap; attach clip to a non-painted surface of the control box.
2. Turn off or remove AC power from the battery charger.
3. Remove the negative (-) battery cable from the set starting battery.
4. Disconnect harness connectors; remove and replace the circuit board.
5. Recalibrate per Table 5-1 for the circuit board replaced.

⚠ Accidental starting of the generator set while working on it can cause severe injury or death.

⚠ The rotor is magnetic and will attract the stator; hold the stator firmly.

1. Disconnect the starting battery cables (negative [-] first).
2. Remove the PMG cover and disconnect the leads at the connector.
3. Remove the bolts and clamps securing the PMG stator to the generator frame; pull away the stator.
4. Remove the rotor center bolt and pull away the rotor.
5. Put the magnetic rotor in a clean plastic bag until remounted.

Tools: Diode, 3 amp fuse, 12 VDC battery

1. Shut down the set and disconnect the AVR.
2. Apply 110 to 220 VAC for one to two seconds to the X and XX leads of the exciter stator.
3. Use a diode to establish correct polarity and a 3 amp fuse to prevent over-excitation.
4. Alternatively, with the set running and no load, apply a 12 VDC battery for one to two seconds.
5. Polarity must be correct: + to X, - to XX.

1. Apply force to the inner race of the rotor bearing when pressing it onto the shaft.
2. Torque drive disc-to-rotor bolts to 190 ft-lbs (257 Nm).
3. Torque drive disc-to-flywheel bolts to 50 ft-lbs (67 Nm).
4. Torque exciter stator mounting screws to 7 ft-lbs (10 Nm).
5. Torque generator end plate mounting bolts to 25 ft-lbs (34 Nm).
6. Ensure the rubber O-ring is in place in the bearing bore.
7. Torque generator mounting bracket bolts to 65 ft-lbs (88 Nm) if M12 or 35 ft-lbs (47 Nm) if M10.
8. Torque generator-to-adaptor bolts to 40 ft-lbs (55 Nm).
9. Torque adaptor-to-engine bolts to 35 ft-lbs (48 Nm).
10. Reconnect the generator as required.