Cummins/Onan 605MCCK Generator Set

⚠ If a voltmeter is not available, use the same procedure but mark the point where arcing begins.

Tools: voltmeter

1. With the generator end cover and band removed, connect a voltmeter across the DC terminals.
2. Start the unit and apply full rated load.
3. Loosen the brush rig mounting screws and rotate the rig to get the highest voltage.
4. Rotate the rig in one direction until the voltmeter reading starts to decrease; mark this point.
5. Repeat step 3 in the other direction.
6. Half the distance between the two marked points is the neutral position.

⚠ Don't force the needle valves against their seats; this will bend the needle.

1. If the carburetor is completely out of adjustment, open both needle valves 1 to 1-1/2 turns off their seats to permit starting.
2. Allow the engine to warm up with the ignition system and governor adjusted.
3. Apply a full load; turn the main adjustment in until speed drops slightly below normal.
4. Turn the needle out until speed returns to normal.
5. With no engine load, turn the idle adjustment out until speed drops slightly below normal.
6. Turn the needle in until speed returns to normal.

Tools: voltmeter and/or frequency meter, tachometer

1. Run the plant 15 minutes under light load to reach normal operating temperature.
2. Adjust the carburetor main jet for best fuel mixture at full rated load.
3. Adjust the carburetor idle needle under no-load condition.
4. Adjust the length of the governor linkage.
5. Check the governor linkage and throttle shaft for binding or excessive looseness.
6. Adjust the governor spring tension for rated speed at no-load with the booster disconnected.
7. Adjust the governor sensitivity.
8. Recheck the speed adjustment.
9. Set the carburetor throttle stop screw.
10. Set the vacuum speed-booster.

⚠ The 4-volt coils can be tested on a 6-volt tester; a 12-volt tester will destroy the coil in a few seconds.

Tools: timing light or continuity test lamp

1. Remove the cover from the breaker box.
2. Attain an approximate setting by loosening the mounting screws and shifting the breaker box to align the witness marks.
3. Crank the engine slowly by hand in the direction of crankshaft rotation until the flywheel witness mark and the TC mark are in line.
4. Adjust the ignition breaker point gap width to 0.020 inches at full separation.
5. Turn the flywheel until the timing mark is about two inches past the 25 degree mark on the gear cover.
6. Turn the flywheel slowly to the right and note if the points just separate when the mark aligns with the 25 degree mark.
7. Shift the breaker box slightly right to retard or left to advance the timing, then tighten the mounting screws.

1. Loosen the lock nut on the slotted stud located just below the governor linkage.
2. Turn the stud in to increase oil pressure, out to decrease pressure.
3. Always tighten the lock nut after making an adjustment.

Tools: drill or drill bit shank

1. Do not attempt adjustments until the engine has been shut down for at least one hour; adjust with the bimetal at ambient temperature.
2. Remove the flame arrester and adapter to expose the carburetor throat.
3. Loosen the screw which secures the choke body assembly.
4. Use a drill or the shank of a drill bit to measure the choke opening.
5. For a richer mixture turn the choke body clockwise; to lean it turn counterclockwise.
6. Tighten the screw that secures the choke body.

Tools: feeler gauge, standard automotive type wrench

1. Remove the valve covers.
2. Crank the engine over slowly by hand until the left intake valve opens and closes.
3. Continue about 1/4 turn until the mark on the flywheel and the TC mark on the gear cover are in line.
4. Check clearance: the thinner gauge should pass freely between the valve stem and tappet but the thicker gauge should not.
5. Turn the self-locking adjusting screw as needed to obtain the right clearance.
6. Crank the engine over one complete revolution and line up the marks again to adjust the right cylinder valves.

Tools: tank of known capacity

1. Install a tank of known capacity at the water outlet.
2. Run the engine until the thermostat opens.
3. Measure the time necessary to fill the tank to obtain flow in gallons per minute.
4. If water flow is below 3.5 GPM, check pump operation and inspect passages and water lines for clogging.
5. To test for air leaks, insert the cooling system outlet into a tank of water and watch for bubbles.

Tools: pressure gauge or manometer

1. Disconnect the pump outlet line and install a pressure gauge.
2. Operate the priming lever a few times while watching the pressure; it should not drop off rapidly.
3. Run the engine at governed speed on the fuel remaining in the carburetor and measure the fuel pump pressure.
4. Pressure should be between 2 and 3 psi with the gauge held 16 inches above the fuel pump.

Tools: thermometer, water bath

1. Place a thermostat and a thermometer in a water bath.
2. The thermostat should start to open at 145 deg F and be fully open at 165 deg F.
3. It should close immediately when removed from hot water.
4. Replace the thermostat if it does not operate properly.

Tools: hack saw blade undercutting tool

1. Undercut the mica between commutator bars as soon as the mica touches the brushes.
2. Make a suitable undercutting tool from a hack saw blade.
3. Avoid injury to the surfaces of the copper bars and leave no burrs along the bar edges.
4. Undercut mica whenever the commutator is refinished.

1. Drain and fill the fresh water system with radiator cleaner.
2. Always flush the cooling system to wash out deposits loosened by chemical cleaning.
3. Remove the water outlet hose from the engine water jacket to the heat exchanger.
4. Flush both the fresh water side and the raw water side of the heat exchanger.
5. Remove the rubber impeller pump cover to flush the raw water side.
6. Also flush the water-cooled exhaust manifold, then check the system thoroughly for leaks.