Cummins/Onan NHEL Generator Set

Tools: vacuum source, drill rod, pliers

1. Apply at least 100 mm mercury vacuum to choke breaker.
2. Insert 8.6 mm drill rod between choke plate and throat.
3. Bend link until choke plate lip touches drill rod.
4. Use two pliers to bend link.

⚠ Ignition adjustments should be made with the engine in a static condition and cold.

⚠ Make sure feeler gauge is clean and free of any grease, oil or dirt.

Tools: Allen head wrench, Flat thickness gauge (feeler gauge), Hex-head socket and socket wrench

1. Disconnect negative (-) battery cable at battery terminal.
2. Remove breaker box cover clip and lift off cover.
3. Remove spark plugs; turn rotor through-bolt clockwise until breaker point gap is open maximum.
4. Remove condenser mounting screw and disconnect condenser and ignition leads; lift out condenser.
5. Remove breaker points mounting screws and lift out point assembly.
6. Replace condenser and point assembly in reverse order of removal.
7. Use allen head wrench to adjust set screw to obtain the gap setting specified in Section 2 Specifications.
8. Measure point gap with a flat thickness gauge; clean points after adjusting.
9. Timing is set during initial engine assembly and fixed by point gap adjustment; no other adjustment necessary.
10. Replace point box cover, spark plugs, and spark plug leads.
11. Connect negative (-) battery cable to negative battery terminal.

⚠ Forcing mixture screws tight damages needle and seat.

Tools: voltmeter, frequency meter, load bank

1. Stop set and connect voltmeter, frequency meter, and load bank.
2. Start set and apply full load; adjust governor speed nut to 59 (49) ±2 Hz.
3. Remove main adjustment limiter cap; turn main screw inward until voltage or frequency drops.
4. Turn outward until voltage or frequency drops again; locate highest point.
5. Turn main adjustment screw out another 1/4 turn.
6. Remove load and verify frequency within 62-63 Hz (51.5-52.5 Hz).
7. Adjust idle screw for smoothest operation without hunting.
8. Replace limiter caps with lever at mid position.

⚠ Forcing the mixture adjustment screws tight will damage the needle and seat; turn in only until light tension is felt.

Tools: Voltmeter, Frequency meter, Load bank, Screwdriver

1. Stop set and connect voltmeter, frequency meter, and load bank to generator output leads.
2. Start set and apply full load; verify frequency within 59 ± 2 hertz, adjust governor speed nut if necessary.
3. Turn main adjustment screw inward until voltage or frequency drops; locate highest point, then turn out an additional 1/4 turn.
4. Remove load and verify frequency within 62 ± 1 hertz; adjust governor speed nut if necessary.
5. Turn idle adjustment screw inward until voltage and frequency drop and engine runs rough or hunts; back out for smoothest operation.
6. Pull governor linkage forward so throttle lever rests against throttle stop screw; adjust stop screw for 55 hertz and 100 (±4.5) volts.
7. Release governor linkage, set voltage and frequency, adjust governor sensitivity.
8. Add and remove a full load several times to make certain set does not bog down or hunt.

⚠ Forcing the mixture adjustment screws tight will damage the needle and seat; turn in only until tension is felt.

Tools: Voltmeter, Frequency meter, Load bank, Screwdriver

1. Turn mixture screws in until lightly seated for preliminary adjustment.
2. Turn main adjustment screw out 2-1/2 (±1/4) turns and idle adjustment screw out 1 (±1/4) turn.
3. Start engine and run about 10 minutes at light load.
4. Connect voltmeter, frequency meter, and load bank; start set and apply full load; verify frequency within 59 ± 2 hertz.
5. Turn main adjustment screw inward until voltage/frequency drop, then outward until they drop again; set at highest point.
6. Remove load and verify frequency within 62 ± 1 hertz; adjust governor speed nut if necessary.
7. Turn idle adjustment screw inward until voltage/frequency drop and engine runs rough; back out until engine runs smoothly without hunting.
8. Pull governor linkage forward so throttle lever rests against throttle stop screw; adjust stop screw for 55 hertz and 100 (±4.5) volts.
9. Release linkage, set voltage and frequency, adjust governor sensitivity; add and remove half load several times.

1. Stop set and allow to cool.
2. Remove plastic choke cover and loosen heating element cover screws.
3. Rotate heating element until choke plate is halfway open.
4. Rotate cover counterclockwise while tapping choke lever until it no longer bounces.
5. Refer to Table 6-2 to determine degrees clockwise from reference.
6. Rotate element cover as specified and tighten screws.
7. Move choke lever to test free operation; install plastic cover.

Tools: Vacuum source (4 to 18 inches Hg), Measuring gauge

1. Remove the complete air filter assembly to provide access to the choke plate.
2. Disconnect diaphragm hose from intake manifold and apply 4 to 18 inches (102 to 457 mm) Hg vacuum to the diaphragm.
3. Apply light finger pressure against the choke lever to take up all freeplay in the pull-off linkage.
4. Check alignment of diaphragm stem, pull-off linkage, and slot in choke lever; correct as required.
5. Measure distance between choke plate and bottom of carburetor; bend diaphragm mounting bracket to obtain 0.39 to 0.43 inches (9.9 to 10.9 mm) clearance.
6. Move choke lever back and forth to check for free movement; verify choke does not bind or stick.
7. Remove vacuum supply from diaphragm and install filter assembly on carburetor.

1. Connect rated load; load watts = volts x amps (1.0 power factor).
2. Check droop from no-load frequency.
3. If droop more than 3 Hz (BGE) or 4 Hz (NHE), turn governor sensitivity screw one turn counterclockwise.
4. Disconnect load and readjust governor speed screw to 62-63 Hz no-load if necessary.
5. If droop less than 2 Hz (BGE) or 3 Hz (NHE), turn sensitivity screw one turn clockwise.
6. Check governor response under 1/4, 1/2 and 3/4 rated loads.

⚠ Disconnect voltage/frequency sensitive devices before adjustments.

1. Set altitude adjust knob (gasoline only) to your altitude.
2. Disconnect all loads and check no-load frequency.
3. Turn governor speed adjusting screw to obtain 62-63 Hz (51.5-52.5 Hz for 50 Hz).
4. Check output voltage; see Generator if not within 10 percent of rated.
5. See Troubleshooting if engine runs roughly.

Tools: frequency meter, voltmeter

1. Set altitude adjust knob to altitude (gasoline only).
2. Disconnect all loads and check zero amps.
3. Adjust governor speed screw for 62-63 Hz no-load (51.5-52.5 Hz).
4. Check output voltage within 10 percent of rated voltage.

⚠ Use extreme caution when making adjustments while the engine is running; hot exhaust pipes or moving parts can cause severe personal injury.

Tools: Voltmeter, Frequency meter

1. Run unit about 10 minutes under light load to reach normal operating temperature.
2. Adjust carburetor fuel mixture screws before governor adjustments.
3. Adjust length of governor linkage and check for binding or excessive looseness.
4. With engine stopped and tension on governor spring, adjust ball joint so throttle shaft stop almost touches carburetor stop.
5. With warmed-up unit at no load, adjust speed adjustment nut to obtain 62 hertz and 127.5 (±4.5) volts.
6. Check frequency and voltage first with load then with no load; must stay within Table 6-1 limits.
7. Adjust governor sensitivity screw to give closest regulation without causing hunting (counterclockwise increases sensitivity).
8. Recheck the speed setting and readjust if necessary.
9. Set carburetor throttle stop screw as specified in Fuel System section.

⚠ Too much pressure on rod can result in faulty adjustment.

1. Loosen lock nut at ball joint end of governor rod.
2. Unsnap socket from ball.
3. Push governor rod gently towards carburetor (full-throttle).
4. Turn socket to lengthen or shorten rod so ball and socket line up.
5. Snap socket back over ball.
6. Tighten lock nut while holding socket square.
7. Rotate governor arm and check for binding; repeat if necessary.