Nowadays, excavators mostly use electronic injection engines. Various alarm codes may be encountered during use, and these alarms are mostly caused by sensor or solenoid valve failures. This article will introduce the functions of engine oil pressure switch, CPU main speed sensor, boost pressure sensor and SCV valve. When the excavator has an alarm code, after knowing the meaning of the code, it can be checked and replaced according to the position of the sensor and solenoid valve.
1. Oil pressure switch
The oil pressure switch is a normally closed pressure switch. Detect the engine oil pressure and feed back the signal to the CPU. After receiving the abnormal signal, the CPU will control the display screen to give an alarm, and the buzzer will give an alarm at the same time. If there is a signal of low oil pressure when the engine is started, in addition to the alarm, the engine will be controlled automatically.
2. CPU main speed sensor
The CPU main speed sensor is used to feed back the engine speed signal to the CPU. After receiving the feedback signal from the main speed sensor, the CPU compares it with the speed set in the program to determine whether the engine speed is normal and whether the engine load is normal. And combined with other feedback signals to make the relevant control of the engine and hydraulic system. Under abnormal conditions, the hydraulic system will be controlled to reduce horsepower or the engine will be controlled to stop.
3. Boost pressure sensor
The boost pressure sensor is used to feed back the suction pressure boosted by the supercharger to the ECU. The ECU judges whether the intake system is normal after receiving the feedback signal from the boost pressure sensor. In combination with other feedback signals, it controls the injection amount, EGR opening, SCV valve, etc. of the engine. Under abnormal conditions, the engine will be controlled to reduce the output.
4. SCV valve
The SCV valve is used to control the inlet diesel flow of the engine diesel fuel feed pump. The SCV valve is an anti proportional solenoid proportional valve controlled by the ECU. The ECU receives engine speed, water temperature, common rail pressure, suction pressure and other signals, exports command current to the SCV valve, and controls the opening of the SCV valve. In order to control the diesel flow into the fuel supply pump and regulate the common rail pressure. Under abnormal conditions, the engine output will drop, or even stop.
