Cummins/Onan MDJC Generator Set

⚠ Do not force needles against seats.

1. Open both needles 1 to 1-1/2 turns off seats.
2. Apply full load; turn main fuel screw in until speed drops, then out to normal.
3. Remove load; turn idle screw out until speed drops, then in to normal.

1. Loosen locknuts on governor linkage, remove link at one ball joint.
2. Position governor arm and fuel control arm fully forward.
3. Adjust linkage so both ball joints fit without moving arms.
4. Tighten locknuts.
5. Release fuel solenoid plunger.

Tools: feeler gauge, socket wrench

1. Turn flywheel to compression stroke for cylinder to adjust.
2. Turn flywheel clockwise additional 10 to 45 degrees.
3. Loosen locknut to increase clearance, tighten to reduce.
4. Use feeler gauge to set proper gap.
5. Adjust in firing order 1-2-4-3.

Tools: feeler gauge, wrench

1. Remove valve covers.
2. Crank engine until intake valve opens and closes.
3. Continue 1/4 turn until timing marks align.
4. Turn adjusting screw to obtain correct clearance.
5. Use flat feeler gauge between valve and valve rotator.

1. With set stopped, turn lever counterclockwise; set screw so plates are closed but not binding.
2. Check lever has approximately 30 degrees travel counterclockwise from vertical.
3. Start set; lever should rotate approximately 60 degrees clockwise from stopped position.
4. Check solenoid plunger is fully seated.
5. If not, adjust distance between plunger and lever arm; repeat steps.

⚠ Avoid overcharging.

Tools: DC ammeter

1. Set slide tap on resistor R4 to about 2 amperes charging rate.
2. For frequent starts, increase charge rate slightly until battery stays charged.
3. Stop engine when readjusting to avoid shorts.

1. Turn idle mixture screw out 3/4 to 1 turn from seated.
2. Turn main mixture screw 1-1/2 to 1-3/4 turns out from seated.
3. Start set; adjust governor spring for 1860 RPM no load (62 Hz or 130 volts).
4. Hold governor arm so throttle lever rests on stop; adjust idle stop screw to 1500 RPM (50 Hz or 100 volts); release.
5. Adjust idle mixture screw to highest RPM or voltage; readjust governor spring to 1860 RPM no load.
6. Apply full load; adjust main mixture screw to highest RPM or voltage; readjust governor spring to 1770 RPM full load.
7. Remove and add load several times to check hunting; readjust governor spring if required.

⚠ If the screw is tightened more than 1 turn, the exhaust valve could hit the piston.

Tools: Feeler gauge

1. Set valves to correct clearance and leave flywheel at 10° ATC.
2. Set the arm in the decompression position.
3. Turn the set screw so the end just touches the exhaust rocker arm.
4. Turn the screw exactly 1 revolution clockwise.
5. Hold the set screw and tighten the lock nut hand tight, then 1/4 to 1/2 turn farther.
6. Release the mechanism and check clearance between screw and rocker arm.

1. Install pump with 0.006-inch (0.15 mm) shims.
2. Loosen delivery valve holder to relieve spring pressure.
3. Rotate flywheel to about 15 degrees before port closing point.
4. Blow in pump inlet and rotate flywheel slowly clockwise until air stops.
5. Measure distance from port closing point to PC mark.
6. Select shims from table and install pump.

⚠ A too close sensitivity adjustment approaching no speed drop can cause hunting.

1. Adjust for minimum speed drop without a hunting condition.
2. If speed drops too much at full load, unscrew the governor adjusting stud to use more coils of the spring.
3. Hold the stud and turn the speed nut slightly for more spring tension to compensate for reduced rpm.

Tools: Tachometer

1. Hold the governor spring stud and turn the nut clockwise to increase rpm.
2. Turn the nut counterclockwise to reduce governed speed.
3. Hold a tachometer against the stud in the axis of the generator.

1. Remove flywheel and examine breaker points.
2. Adjust gap to .022 inch (0.56 mm) at full separation.
3. Loosen screw to shift point set, retighten securely.