(1) Start the system. If the engine can't start, we must first doubt the starting system, mainly to judge whether the starter can rotate normally. There are two situations: the first is that the starter does not turn, which may be caused by the failure of the starting circuit or the starter itself; The second is that the starter can rotate, but it may not. At this time, the starter should be disassembled to check whether the speed and torque of the starter meet the requirements. If it meets the requirements, the fault may not be in the startup system.
(2) Ignition system. It may be that the ignition timing is incorrect, and the ignition energy of the spark plug is weak or unable to ignite, which will cause the starter to fail to start. Incorrect ignition timing may be caused by incorrect setting or failure of vehicle speed sensor. The spark plug is weak or does not ignite, which may be the fault of the spark plug itself, or the leakage of the ignition circuit and poor contact.
(3) Fuel supply. Low fuel pressure or faulty fuel injectors may cause the engine to fail to start. The fuel pressure is too low, which may be caused by fuel filter blockage, oil pipe leakage or oil pressure regulator failure. The failure of fuel injector may be caused by the blockage of fuel injection hole and the burning of solenoid valve coil.
(4) Other aspects. The air filter is blocked seriously, and the cylinder compression pressure is low, which will cause the motor to fail to start.
2 Analysis of troubleshooting ideas for engine failure to start
(1) Conduct routine inspection first. Mainly check whether the battery voltage is sufficient, whether the fuse box and relay box are ablated, whether the main circuit leads are loose, poorly contacted and poorly grounded, whether the air filter is blocked, whether the oil quantity is sufficient, whether the fuel quantity is sufficient, and whether the oil pipes and water pipes are leaking oil.
(2) Check the startup system.
① Take out the fuel pump relay from the fuse box;
② When the gear lever is in the N or P position (A/T) or the clutch pedal is depressed (M/T), turn the ignition switch to the STATR position. If the starter drives the engine to rotate normally, the starting system is normal. If the starter doesn't drive the engine at all, proceed to the next step. If the flywheel ring gear cannot be separated when the key returns, check whether the iron core and switch are faulty, whether the driving gear is polluted or whether the one-way clutch is damaged.
③ Check the battery status. Check the connection parts of the battery electrical components, the negative battery wire harness connected to the car body, the engine grounding wire harness and the connecting wire harness of the starter for looseness and corrosion, and test here. If the starter drives the engine to rotate normally, the starting system is normal; If the starter still can't drive the engine to rotate, proceed to the next investigation.
④ Disconnect the S terminal connector of the electromagnetic switch. Short circuit terminal b and terminal s of electromagnetic switch with jumper wire. If the starter drives the engine to rotate, proceed to the next step. If the starter still cannot drive the engine to rotate, remove the starter and repair or replace it as needed.
⑤ Check the following items in turn until an open circuit is found. Check the harness and connectors between the fuse/relay box under the driver's seat and the ignition switch and between the fuse/relay and the starter. Check the ignition switch. Check transmission gear switch connector or ignition lock switch connector. Check starter relay.
(3) Check the ignition system. First, check and adjust the ignition timing, and then remove the spark plug for flashover test. If the flashover is abnormal, check the electrode gap of the spark plug, which should be between 1.0 ~ 1.0~ 1 1 mm If the gap is normal, check the resistance between the high-voltage line and the ignition coil: measure the resistance of the primary coil between terminals (+) and (-).
(4) Fuel supply system. Check the oil pressure in the oil circuit. If the oil pressure is normal, check whether the injector is faulty. If the oil pressure is abnormal, check whether the fuel filter and oil pressure regulator are faulty.
(5) If there is nothing wrong with the starting, ignition and oil circuit, it is necessary to check whether the filter has mechanical failure and check the pressure of each cylinder.
Hope to adopt, thank you!