Cummins/Onan YD series Generator Set

⚠ Batteries emit highly explosive hydrogen gas. Never smoke near a battery, and keep sparks, flames and other sources of ignition away.

1. Locate the battery charge rate adjusting resistor in the outlet of the generator cooling blower.
2. Shut down the set before adjusting the slide tap.
3. Adjust the slide tap up to increase the charge rate if necessary to maintain a specific gravity of at least 1.260.
4. Keep battery terminals clean and tight; apply a light coat of vaseline to retard corrosion.
5. Fill the cells with distilled water to keep the electrolyte level up to the split rings.

Tools: Filtered low pressure compressed air, Torque wrench

1. Remove the generator end cover for access to the rotating rectifiers.
2. Use filtered, low pressure compressed air to blow away accumulated dust on the diodes.
3. Torque the diode studs to 25 ft-lbs (33 Nm).

⚠ Hot oil can cause burns. Shut down the set before checking the oil level to prevent hot oil from blowing out on you.

1. Drain the crankcase oil while the engine is still hot.
2. Refill with oil of the correct API designation and SAE viscosity grade suitable for the ambient temperature.

1. Lightly oil the gasket.
2. Turn the filter on by hand until the gasket just touches the block.
3. Tighten 1/2 turn more.

1. Perform all scheduled maintenance.
2. Change the oil and attach a tag indicating the viscosity grade.
3. Pour one ounce of rust inhibiting oil (or SAE Grade 10) into each cylinder, crank the engine several times and replace the spark plugs.
4. Plug the exhaust outlet to prevent the entrance of insects, dust and moisture.
5. Lightly wipe with grease or oil metal parts that would otherwise rust.
6. Disconnect the battery (negative [-] cable first) and store it following standard procedures.
7. Cover the set to protect it from dust and moisture.

1. Unplug the exhaust and remove the protective cover.
2. Change the oil if the viscosity grade recorded on the tag is not suitable for the current ambient temperature.
3. Service the battery and connect it (negative [-] cable last).
4. See Operation for starting and operating the set.

⚠ Running the set continuously with less than 1/2 full rated load during the first hundred hours can result in poor seating of the piston rings and consequent problems with ring blowby and high oil consumption.

1. Connect 1/2 of the full rated load for the first half hour of operation.
2. Connect 3/4 of the full rated load for the next half hour of operation.
3. Operate with the full rated load connected any time thereafter.
4. Drain and replace the engine oil after the first 50 hours of operation.

1. Select the fuel to be used and close the supply valve for the other fuel.
2. Engage the choke lock wire to keep the choke open when using gas fuel and release it when using gasoline.

⚠ Overloading can cause the generator to overheat and fail. The load may exceed the nameplate rating only momentarily, such as during the starting of a large motor.

1. When possible, allow the set to warm up before connecting the full load.
2. When possible, connect the load in steps.
3. Occasionally connect the full rated load to burn off carbon deposits formed in the exhaust system during light-load operation.

⚠ Pressure cooled engines can quickly overheat and be damaged if run without the front air shroud/access cover in place.

1. Check the fuel and oil levels.
2. Make sure all the air shrouds and service access covers are in place.
3. Press the START/STOP switch to START until the engine starts; the starter is disengaged automatically by the start disconnect switch.
4. Do not crank for more than 30 seconds at a time; allow 60 seconds between cranks.
5. A new set may not start right away if spark plug electrodes are coated by rust inhibiting oil; remove spark plugs and clean the oil off.
6. The oil pressure gauge should indicate at least 20 psi.
7. Connect the load and follow the break-in procedure for initial start-up.

1. Disconnect the load and let the generator set run for 10 minutes to cool off.
2. Press the START/STOP switch to STOP until the engine stops.
3. If a safety circuit stops the engine (high engine temperature or low oil pressure), determine the cause and service or repair before returning the set to service.