1. Fault Phenomena
The engine cannot start because the starting motor is not running.
2. Start-up system circuit diagram
The starting system circuit diagram is shown in Figure 1-1.
3. Fault diagnosis and troubleshooting
(1) First check whether the fuse in the circuit is fused or not. If the fuse is fused, the start switch will be powered off and the starting motor will not run and the engine will not start. After replacing the fused fuse again, the starting motor will run and the engine will start. If the starting motor still does not run after replacing the fuse, the next check should be carried out.
(2) Check whether the battery voltage is above 24V and the density of electrolyte is 1.26. × 10kg/m2. If the density is not in accordance with the regulations, the battery capacitance is too low or there are other faults. The battery should be charged or replaced.
(3) If both the battery voltage and the density of electrolyte are normal, turn the start switch from the on position to the off position and observe whether the battery relay acts or not.
(4) If there is no sound from the battery relay, further check whether the voltage at terminal B of the start switch is within the range of 20~29V (positive terminal of the multimeter is connected to terminal B of the start switch and negative terminal is connected to the negative terminal of the battery). If the voltage is not normal, check positive terminal M11-M7 (1) of the battery, fuse M1. (1) Whether there is bad contact or open circuit in the wiring harness between terminal B of startup switch, after repairing or replacing the wiring harness, the startup motor can run and the engine can start.
(5) If the voltage of terminal B of startup switch is in the range of 20~29V, further check whether there is continuity between terminal B of startup switch and terminal BR (turn on startup switch and remove terminal B). If not, there is a fault between terminal B of startup switch and terminal BR. After replacing the startup switch, the startup motor can run.
(6) If there is continuity between the startup switch terminal B and the terminal BR, further check whether the resistance of the wiring harness between the startup switch terminal BR and the battery relay terminal is normal. (Maximum resistance between starting switch terminal BR and battery relay terminal is 1Ohm, minimum resistance between wiring harness and chassis is 1MOhm, open both ends of switch and battery relay). If resistance is abnormal, further check starting switch terminal BR-M1(2) -M20-D10-M7. (2) Whether there is bad contact or open circuit between terminals of a battery relay, after repair or replacement, the starting motor can run and the engine can start.
(7) If the resistance value of the wiring harness between the starting switch terminal BR and the battery relay terminal is within the standard range, further check whether there is conductivity between the negative terminal of the battery and the terminal-b of the battery relay. If not, check whether the wiring harness between the negative terminal of the battery and the terminal-b of the battery relay has poor contact. The starting motor can be transported after repair or replacement. Turn around and the engine will start.
(8) If there is conduction between the negative terminal of the battery and terminal-b of the battery relay, the battery relay is faulty. After replacing the battery relay, the starting motor can run and the engine can start.
(9) If the battery voltage and electrolyte density are normal, when the starting switch is turned from the on position to the off position, the battery relay acts, turn on the starting switch and observe whether the gear of the starting motor moves out. If not, continue to check whether the voltage between terminal C of the starting switch and the chassis is normal. (Turn on the start switch, the voltage is about 24V). If the voltage does not reach 24V, there is a fault between terminal B and terminal C of the start switch. After replacing the relevant components, the start motor can run and the engine can start.
(10) If the voltage between starting switch terminal C and chassis reaches 24V, check the wiring harness between starting switch terminal C-Ml(4) -M14(1) -E8(1) -M2(1) and starting motor terminal S for poor contact or open circuit. After repair or replacement, the fault can be eliminated.
(11) If the gear wheel of the starter motor moves out, continue to check whether the voltage between terminal B of the starter motor and the chassis is normal (turn on the starter switch, the voltage is 24V). If the voltage does not reach 24V, check the wiring harness between the positive terminal of the battery and terminal B of the starter motor for poor contact, and the fault can be eliminated after repair.
(12) If the voltage between terminal B of the starter motor and the chassis is normal, the starter motor is faulty. The fault can be eliminated by replacing the starter motor and the engine can be started.
