Reinstall the faulty automobile ECU, unplug the water temperature sensor plug, start the engine cold, and the car landed smoothly, but the engine failed at this time.

The obstacle light is on, and the engine fault code is read as "13", indicating that the water temperature sensor is faulty, indicating that the ECU has started the fail-safe system. Start according to the pre-stored value at 20℃, and measure the pre-stored start-up fuel injection amount at 20℃.

The pulse width is17.8 ms. According to the previous inspection, the starting fuel injection pulse width of normal automobile engine at 30℃ is 1 1.5ms, while the measured fuel injection pulse width of automobile at the current temperature of 30℃ is only 8.7ms, which is determined by the following formula.

It is concluded that there is a certain difference between the pre-stored starting fuel injection pulse width in ECU and the starting fuel injection pulse width provided according to the signal of water temperature sensor at the same temperature.

This reflects that ECU can't calculate the fuel injection pulse width corresponding to the starting temperature according to the signal detected during the cold start of the engine, which reduces the fuel injection pulse width, reduces the fuel injection quantity during the start, and dilutes the mixture concentration, which is not suitable for the start-up state. Therefore, it is necessary to start the engine several times until the concentration of the mixed gas increases.