Difficult to start

The influence factors and inspection methods of cold start difficulty and hot start difficulty of stainless steel long axis motor products are basically the same. As far as the mixture concentration is concerned, there are two cases: the mixture is too thin and the mixture is too rich. The faults that affect fuel supply may appear in fuel quality, fuel pump, fuel filter, fuel pressure regulator, cold start system, fuel injector and water temperature sensor; Most of the faults that affect the air intake are air filter blockage, air leakage in the air intake system and idle speed control faults.

1. Fuel pressure regulator failure

The oil pressure of the fuel system has a direct impact on the mixture concentration, so the fuel pressure should be checked first. The method is: first connect the fuel pressure gauge into the fuel pipe, then start the engine and measure the fuel pressure. If the fuel pressure is too high, replace the pressure regulator; When the pressure is too low, clamp the return hose. If the fuel pressure rises to the normal value, the fuel pressure regulator is damaged. Otherwise, check the fuel pump and fuel filter. After shutdown, check that the fuel pressure should be kept at the specified value for 5min, otherwise it means that the injector leaks and the mixture is too rich.

2. Failure of fuel pump and fuel filter

When it is difficult to start, the general fuel pump is able to work normally. The problem is that the filter screen of the fuel pump is blocked, which causes the fuel pump can not absorb enough fuel or the fuel filter is not unblocked, which leads to the insufficient pressure of the fuel supply system.

3. Cold start system failure

In some models, there are cold start injector, which can enrich the mixture to improve the cold start performance. The cold start injector is controlled by the start switch and the thermal time control switch. The injection duration depends on the heating coil current of the thermal time control switch and the temperature of the cooling water.

The main faults of cold start system are as follows: the cold start injector is blocked by colloid, which affects the atomization quality of fuel injection and makes cold start difficult; The cold start injector fails to work normally; The thermal time control switch is short circuited (the contact is normally closed) or open circuited (normally open). If the contact is normally closed, the cold start injector will still be controlled to inject too much fuel during the hot car, resulting in the difficulty of hot start. If the time control switch is short circuited, the cold start injector will never work, resulting in the difficulty of cold start.

4. Injector failure

The general performance of injector failure is as follows: the injector orifice is blocked by colloid, carbon deposit or poor sealing, resulting in dripping, resulting in too small or too large mixture concentration. The detection method is as follows: first, start the engine and check the operation sound at each injector with a stethoscope. If no sound is heard, check the wiring connector, injector or injection signal from ECU; Then, use a multimeter to measure the resistance between the terminals of the fuel injector. If the resistance value is inconsistent with the specified value, replace the fuel injector; After Zui, check the fuel injection quantity of the injector, which should be within the normal range and the difference of fuel injection quantity of each cylinder should be less than 5cm3.

5. Water temperature sensor fault

The water temperature sensor is used to detect the temperature of the cooling water and convert it into a voltage signal related to the temperature, which is input to ECU as the basis for ECU to correct the injection quantity. If the water temperature sensor fails, or the wiring between the water temperature sensor and the ECU is open circuit, short circuit, and the surface scale is serious, the output signal will have a large deviation, so that the fuel injector can not increase or reduce the fuel injection amount in time, resulting in difficult starting.

6. Idle speed control valve (ISC) fault

Most EFI Engines adopt stepper motor idle speed control valve. According to the working conditions of the engine, ECU adjusts the power on sequence of the stepper motor solenoid coil, makes the conical valve body on the stepper motor shaft rotate in or out, and adjusts the opening of the bypass air passage to realize the regulation of the bypass air intake.

If it is difficult to start the engine, but it can be started by stepping on the accelerator slightly, it indicates that the idle speed control valve is faulty. When the ISC valve is disassembled, it will be found that there are more carbon deposits, glue sticking and oil accumulation on the conical surface of the valve body, which reduces the adjustable range of the conical valve, resulting in the starting difficulty due to the reduced air intake and too rich mixture during cold start.