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If it is difficult to start hot, first check the fuel pressure. Connect the fuel pressure gauge to the fuel line first, then start the engine and measure the fuel pressure. If the fuel pressure is too high, the pressure regulator should be replaced; if the pressure is too low, try to clamp the return hose. In this case, if the fuel pressure rises to the normal value, the fuel pressure regulator is damaged, or the fuel can be checked. Pumps and fuel filters. After stop, check the fuel pressure should be maintained at the specified value, otherwise the injector leakage, resulting in over-rich mixture.
If the cold start is difficult, it may be that the cold start injector is blocked by the colloid, which may affect the quality of the spray atomization; or the cold start injector may not work properly or the thermal time switch may be short-circuited or open circuited. If it is an open circuit, control the cold start injector to inject too much fuel and cause start-up difficulties; if it is a short circuit, the cold start injector will not work and it will cause difficulty in starting.
In addition, there may be fuel injector failures. Injector faults usually manifest as: injector nozzle is blocked, carbon deposit or lax seal causes drip, resulting in too small or too large gas mixture. When testing, you can start the engine first and listen carefully to the sound of each injector. If you can't hear the sound, you should check the wiring connector, fuel injector, etc. Then you can use a multimeter to measure the resistance between the injector terminals if the resistance If the value does not match the specified value, replace the injector. Finally, you can check the injector fuel injection, the value should be within the normal range, and the difference between the injection of each cylinder is less than 5cm.
If the engine can not be started at all, and there is no sign of ignition, it is generally due to fuel injection, which needs to be checked in two ways:
Speed ​​signal system. The engine speed and crankshaft position sensor detect the speed signal and provide the crankshaft position signal when the engine is working, and serve as the main basis and basis for the control system to perform various controls. If the sensor or its circuit fails, the electronic control unit cannot receive the speed signal and the crankshaft position signal, and the fuel injection and ignition timing cannot be properly controlled, and the spark plug will not flash over.
Fuel pump and control circuit. If the fuel pump or the control circuit fails, the fuel may not be ejected normally or it may not start even if the injector is operating normally. You can check the pressure in the inlet hose. If there is pressure in the hose and you hear the sound of oil return, it means there is no problem with the fuel pump. Otherwise, you can check the fuel pump again. If the fuel pump is working properly, check the control circuit, including fuses, main relays, fuel pump relays, resistors, and wiring and connectors. After these careful inspections, you can generally find the fault.
When the engine startup problem occurs, the general situation is whether it is difficult to start or whether it can not be started completely. This is helpful for analyzing failures. If it is only difficult to start but it can be started reluctantly, there is a high possibility of problems with the fuel or the filter. In the case of mixed gas concentrations, there may be cases where the mixture is too dilute and the mixture is too concentrated. Failures that affect oil supply may occur on fuel quality, fuel pumps, fuel filters, fuel pressure regulators, cold start systems, fuel injectors, and water temperature sensors; faults that affect the intake air are mostly air filter clogging, Intake system leakage and idle speed control failure.