Most of the tests of the electrical system can be done on the engine. The wiring insulation must be in good condition. The wire and cable connections must be clean, and both components must be tight. The battery must be fully charged. If the on-engine test shows a defect in a component, remove the component for more testing.
The starting system consists of the following components:
- Starting motor solenoid
- Starting motor
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237-5130 Digital Multimeter or the 146-4080 Digital Multimeter
The 237-5130 Digital Multimeter Gp and the 146-4080 Digital Multimeter Gp are portable hand-held service tools with a digital display. These multimeters are built with extra protection against damage in field applications. Both multimeters are equipped with 7 functions and 29 ranges. The 237-5130 Digital Multimeter Gp and the 146-4080 Digital Multimeter Gp have an instant ohms indicator. This indicator permits checking continuity for a fast inspection of the circuits. These multimeters can also be used for troubleshooting capacitors that have small values.
Note: Refer to Special Instruction, SEHS7734 for complete information for the use of the 237-5130 Digital Multimeter . Refer to Operation Manual, NEHS0678 for complete information for the use of the 146-4080 Digital Multimeter .
Use the multimeter in the DCV range to find starting system components which do not function.
Move the start control switch in order to activate the starting solenoids. The starting solenoid’s operation can be heard as the pinions of the starting motors are engaged with the ring gear on the engine flywheel.
If a solenoid for a starting motor will not operate, it is possible that the current from the battery did not reach the solenoid. Fasten one lead of the multimeter to the terminal connection for the battery cable on the solenoid. Touch the other lead to a good ground. A zero reading indicates that there is a broken circuit from the battery. More testing is necessary when there is a voltage reading on the multimeter.
The solenoid operation also closes the electric circuit to the motor. Connect one lead of the multimeter to the terminal connection of the solenoid that is fastened to the motor. Touch the other lead to a good ground. Activate the starting solenoid and look at the multimeter. A reading of the battery voltage shows that the problem is in the motor. The motor must be removed for further testing. A zero reading on the multimeter shows that the solenoid contacts do not close. This is an indication of the need for repair to the solenoid or an adjustment to be made to the pinion clearance for the starting motor.
Perform a test. Fasten one multimeter lead to the terminal connection for the small wire at the solenoid and fasten the other lead to the ground. Look at the multimeter and activate the starting solenoid. A voltage reading shows that the problem is in the solenoid. A zero reading indicates that the problem is in the start switch or the wires for the start switch.
Fasten one multimeter lead to the start switch at the terminal connection for the wire from the battery. Fasten the other lead to a good ground. A zero reading indicates a broken circuit from the battery. Make a check of the circuit breaker and wiring. If there is a voltage reading, the problem is in the start switch or in the wires for the start switch.
Starting motors that operate too slowly can have an overload because of too much friction in the engine that is being started. Slow operation of the starting motors can also be caused by a short circuit, loose connections and/or dirt in the motors.