Willys-Overland MB-441 Engine Engine

• Voltmeter 3F8300-14
• Testing stator windings for short-circuit. Touch one test prod to terminal No. 4 and the other to terminal No. 5. If the lamp lights, the two windings are shorted together.
  Fix: Connect terminal No. 4 to No. 5. Connect terminal No. 7 to one terminal of the battery. If there is a large flash or spark, both windings are short-circuited and, the No. 8 terminal should not be held in contact with the battery terminal. If there is only a small flash or spark, connect No. 8 terminal with the battery. Then, with a good d-c voltmeter, capable of registering with reasonable accuracy voltages from 0 to 8 volts, take voltage readings between terminals No. 4 and No. 8. Both readings should be almost exactly the same, one-half the battery voltage. If one reading is much higher than the other, the winding with the low reading is short-circuited. If tests indicate a short-circuit, inspect the cables throughout their lengths.
• Testing rotor windings for grounds. Touch one test prod to the rotor shaft and the other prod to the collector ring. If the lamp lights, the alternator field winding is grounded.
  Fix: Touch one test prod to the rotor shaft and‘the other prod to the exciter commutator. If the lamp lights, the exciter armature winding or the commutator is grounded.
• Testing exciter field windings for grounds. Disconnect the shunt field lead near the upper left exciter brush holder and the series field lead near the lower left brush holder. Disconnect the heavy exciter lead from the right-hand terminal of the solenoid starting switch. Touch one test prod to the exciter frame and the other test prod to any of the field leads. If the lamp lights, the winding is grounded.
  Fix: Inspect the leads. If the ground is in a lead, tape the defective section with several layers of half-lapped rubber tape, then with two layers of friction tape. If the ground is in the winding proper, notify the person in authority.
• Testing alternator field winding for short-circuit. If a consicorahie number of turns in one coil are short-circuited, that.coil will run cooler than other coils that are in good condi- tion.
  Cause: Grounds at two points in the winding would short-circuit the intervening portion and the winding would test grounded.
• Switch, rheostat, toggle 3Z9859-8
• STARTER FUNCTIONS BUT ENGINE WILL NOT START.
  Cause: No spark at plugs. Ignition switch shorted. Ignition switch in OFF position. Battery not strong enough to supply both starting current and ignition. High-water-temperature switch closed. Low oil supply in crankcase. Low-oil-pressure switch stuck. Ignition breaker points burned or pitted. Ignition breaker points out of adjustment. Defective capacitor in magneto or distributor. Defective magneto.
  Fix: Place jumper across switch terminals. If starter functions, replace switch. Place jumper between battery and starting motor connection on magnetic switch. If starter functions, replace solenoid. Replace starting motor.
• Spark at Spark Plug. Test spark coil. defective.
  Cause: Battery not strong enough to supply both starting current and ignition.
  Fix: Check battery. Replace with fully charged battery.
• Running time meter 3H1920/M 10
• Rheostat 3Z7230-2
• Other tests. The same equipment may be used for many other tests for grounds, open circuits, or short circuits elsewhere on the power unit.
  Fix: When the lamp lights, obviously the circuit between the prods is complete and vice versa.
• Multi-breaker 83H912.50
• GENERATOR OVERHEATING.
  Cause: Generator air passages obstructed. Defective generator winding. Lack of ventilation around unit. Faulty lubrication.
  Fix: Check and correct load. Blow out air passages with air hose. Check generator windings (par. 54). Provide better ventilation. Check lubrication.
• GENERATOR OUTPUT NO
  Cause: Fuel line obstructed. Engine overheated. Broken ignition wire. Lack of oil. Circuit breaker open. Lack of excitation. Open circuit, short circuit, or ground in generator. Brushes not seating properly. Broken wire. Defective voltmeter. Defective voltage regulator.
  Fix: Clean fuel line and drain and refill fuel tank. Clean fuel strainer. Locate and correct cause. Inspect ignition wiring. Correct fault. Check oil. Refill crankcase. Close circuit breaker. Inspect exciter brushes and commutator. Clean commutator; replace brushes. See paragraph 54. Check alternator brushes and slip rings. Clean slip rings; replace brushes. Check for broken wire. Repair or replace faulty wire. Try meter known to be satisfactory. Replace defective meter. Switch to manual control. Replace regulator if defective.
• GENERATOR FREQUENCY TOO HIGH OR LOW.
  Cause: Excessive load. Load too great. Engine not operating at proper speed.
  Fix: Check and correct load. Check load lines and remove short. Check engine speed. Adjust engine governor.

Compiled from service & troubleshooting documentation across every generator set that uses the Willys-Overland MB-441.