Cummins/Onan MDKAF Generator Set

⚠ Accidental starting can cause severe personal injury or death. Disconnect the negative battery cable(s).

1. Disconnect negative battery cable(s) and remove belt guard or sound shield door.
2. Loosen the alternator pivot bolt first and then the adjusting bracket bolt on top.
3. Pivot the alternator outwards to tighten belt; hold tension by tightening the adjusting bracket bolt.
4. Apply 20 pounds (10 kg) to the middle of the pulley span; deflection should be 0.4 inch (10 mm). Tighten alternator bolts.
5. Secure belt guard or sound shield door and reconnect battery cables (negative last).

⚠ Incorrect electrical connections/adjustments can cause equipment damage, severe injury or death. Turn off genset and disconnect battery before adjustments.

Tools: Digital volt-ohmmeter, Frequency meter, Small flat-blade screwdriver

1. Identify new frequency and voltage.
2. Replace AC output circuit breaker if necessary for new load.
3. Move 60 Hz/50 Hz switch on regulator board to desired value.
4. Readjust engine speed for new frequency: 50 Hz 1500 RPM, 60 Hz 1800 RPM under no-load and full-load.
5. Apply maximum rated load and adjust frequency fine adjust screw to desired frequency.
6. Remove load and check no-load frequency is within 3 Hz of full-load frequency.
7. Tighten lock nut.

⚠ Accidental starting can cause severe personal injury or death. Disconnect battery cables, negative first.

⚠ Contact with high voltage can cause severe personal injury or death. Do not touch exposed wiring or components.

Tools: Voltmeter, Small flat-blade screwdriver

1. Attach a voltmeter securely to L1 and L2 leads.
2. Start genset and place a typical load on its output.
3. Use a small flat-blade screwdriver to set voltage adjust potentiometer for correct voltage; ideal setting is 117 VAC at 60-61 Hz measured at L1-L0 terminals.

Tools: Voltmeter

1. With starter motor running, check voltage drop from battery negative post to cylinder block.
2. Check voltage drop from battery positive post to battery terminal stud on solenoid.
3. Normally these should be less than 0.3 volts.
4. Clean all connections in any part of circuit showing excessive voltage drop.

Tools: DC voltmeter

1. With engine running, check DC voltmeter.
2. 12-volt system should read 13.5 to 15 volts.
3. Improper output may be caused by loose drive belt, poor terminal connections, broken wires, or defective alternator.

⚠ Ignition of explosive battery gases can cause severe personal injury.

Tools: Hydrometer

1. Check battery charge condition with a hydrometer.
2. Electrolyte specific gravity should be about 1.260 for a fully charged battery at 80°F (27°C).
3. If not, add distilled water to keep electrolyte at proper level, then recharge battery.
4. If battery will not recharge, replace it.

Tools: Pressure gauge 0 to 15 psi (0 to 100 kPa)

1. Disconnect fuel line at outlet of fuel pump and connect pressure gauge at pump outlet. Use gauge calibrated for 0 to 15 psi (0 to 100 kPa). Do not tee into fuel line.
2. Push Start/Stop switch to START and hold several seconds until fuel pressure stabilizes. Fuel pressure should stabilize between 3.5 and 6 psi (24 and 41 kPa).
3. If fuel pressure less than 3.5 psi (24 kPa), check for fuel restrictions. For three feet (0.9 meters) lift, output pressure reduced by 1.0 psi (to 2.5 psi minimum).
4. Relocate pump closer to fuel tank if more than 3 feet (0.9 meters) above end of fuel pickup tube.
5. If pump defective, replace with correct (same part number) Onan pump. Fuel pump is not serviceable in the field.

1. If fuel to injection pump but no fuel at injection nozzle, fuel shutoff solenoid K7 may be defective.
2. Watch for solenoid actuation when B+ applied (start switch in start or run position).
3. Measure voltage at solenoid to confirm start circuit working.
4. If no actuation when B+ applied, fuel solenoid must be adjusted or replaced. When B+ removed, solenoid must de-activate.

Tools: Voltmeter

1. Connect B+ voltage across relay coil terminals. Relay should activate if coil functional.
2. Connect a voltage source to one side of relay contacts.
3. Connect voltmeter to other side of relay contact and to other end of voltage source.
4. Energize relay; NO contacts good if voltage appears, NC contacts good if voltage reading goes to 0.

1. Apply battery positive (B+) to terminal marked S.
2. Connect a ground wire to solenoid terminal marked I. The solenoid should activate.
3. If contacts are good, battery voltage should be present between terminal 1 and ground.
4. Voltage drop across contacts should never exceed one volt in circuit application.

Tools: Ohmmeter

1. Remove battery B+ cable at battery.
2. Place ohmmeter leads across switch.
3. Open and close switch while observing ohmmeter. NO contacts should indicate infinite resistance when open and continuity when closed. NC contacts should indicate continuity when closed and infinite re

Tools: Wheatstone bridge or digital ohmmeter, Megger or insulation resistance meter

1. Disconnect main rotor field leads at F1+ and F2-.
2. Disconnect lead wires from diodes CR1 through CR6.
3. Test between exciter lead pairs T1-T2, T2-T3 and T1-T3; resistance at 77°F (25°C) should be 645 milliohms ± 10%.
4. For grounds, apply test leads between any CR lead and rotor laminations with insulation resistance meter or Megger not more than 500 volts.
5. Reading should be 100,000 ohms or higher. If not, rotor is questionable and may require oven drying and retest.