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. ensure that the batteries have a full charge. 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:
- Keyswitch or Engine Control Switch (ECS)
- Starting motor solenoid
- Starting motor
|Part Number||Part Name||QTY|
|Digital Multimeter Gp||1|
Typical example of the 146-4080 Digital Multimeter Gp or the 237-5130 Digital Multimeter Gp
The 146-4080 Digital Multimeter Gp and the 237-5130 Digital Multimeter Gp are hand-held service tools with a digital display, that is portable. These multimeters are built with extra protection against damage in harsh field applications. The multimeters are equipped with multiple functions and multiple ranges. Both of the digital multimeters 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 the operation manual that is included with each digital multimeter for complete information on the use of the respective digital multimeter.
Use the multimeter in the DCV range to check for voltages at the various components for the electric starting system.
Move the start control switch in order to activate the starting solenoids. The operation of the starting solenoid can be heard as the pinions of the starting motors engage with the ring gear on the engine flywheel.
If a solenoid for a starting motor does not operate, voltage from the battery may not be present at 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 source of battery ground. A zero reading indicates that there is a problem in the wiring from the battery to the solenoid. Correct the problem. If battery voltage is present at the solenoid, continue with this test procedure.
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 source of battery ground. Check the multimeter for a voltage while you attempt to start the engine. A reading that is equal to battery voltage may indicate that there is a problem with the starting motor. Remove the starting motor for testing. If the multimeter does not indicate that battery voltage is present during the test, then the solenoid contacts are not closing. Either the solenoid has a problem, or the pinion clearance must be adjusted.
Perform the following procedure to check for proper operation of the solenoid:
Fasten one multimeter lead to the terminal connection for the small wire at the solenoid and fasten the other lead to battery ground. Check the multimeter for a voltage while you attempt to start the engine. If battery voltage is present at the terminal, then the problem is in the solenoid. If battery voltage is not present during the test, the problem is in the start switch or the wiring for the start switch.
Perform the following procedure to check for proper operation of the start switch:
Fasten one multimeter lead to the terminal for the battery connection at the start switch. Fasten the other lead to a good source of battery ground. If battery voltage is not present at the start switch, there is a problem in the wiring between the battery and the start switch. Check for a circuit breaker that has been tripped. Check the wiring from the battery to the start switch. If battery voltage is present at the start switch, the problem may be the start switch. The problem may be in the wiring between the start switch to the solenoid. Perform the necessary repairs.
Too much mechanical friction from the engine can cause starting motors to drag. Slow operation of the starting motors can also be caused by a short circuit, loose connections and/or dirt in the motors. These conditions can cause starting motors to overheat. Overheating will shorten the life of the starting motor. Perform the necessary repairs in order to correct these conditions.
Trouble with the starting system could be caused by the battery or by charging system problems. If the starting system is suspect, refer to Service Manual, SENR3581, "37-MT, 41-MT & 42-MT Series Starting Motors". This publication contains troubleshooting for the starting system, test procedures, and specifications.