NUT TO VALVE 4N3759 - Caterpillar

Use the multimeter in the DCV range to find the starting system components which do not function.Move the start control switch to activate the starting solenoids. The starting solenoid 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, the current from the battery may not have reached the solenoid. Fasten one lead of the multimeter to the connection (terminal) for the battery cable on the solenoid. Put 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 solenoid connection (terminal) that is fastened to the motor. Fasten 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. Repair the solenoid if the contacts do not close. The clearance for the starter motor pinion gear may also need adjusting.Perform a test. Fasten one multimeter lead to the connecting (terminal) for the small wire to 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 in the wires for the start switch.Fasten one multimeter lead to the start switch at the connection (terminal) for the wire from the battery. Fasten the other lead to a good ground. A zero reading indicates a broken circuit from the battery. Check 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 the following conditions:
A short circuit
Loose connections
Dirt in the motorsTrouble 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.