1. The shutdown solenoid valve is not closed tightly
Why?
The shutdown solenoid valve is not closed tightly, which is one of the main reasons for the difficulty of diesel engine shutting down. When the power is turned off with the key, the power to the solenoid valve electromagnet is cut off, the solenoid valve should be in a closed state, and the oil passage leading to the cylinder head of the fuel is sealed; if the shutdown solenoid valve is not closed tightly, a small amount of fuel will continue to flow to the cylinder head oil passage, making the diesel engine unable to shut down. The shutdown solenoid valve is not closed tightly, in addition to processing reasons, it is also closely related to the cleanliness of the fuel. When the cleanliness of the fuel is low, impurities will invade the solenoid valve, pad the valve plate or make it jammed, causing it to be closed loosely; impurities may also directly invade during maintenance due to carelessness about the cleanliness of the oil passage.
What to do?
When the solenoid valve is not closed tightly and it is difficult to shut down, you can often increase the throttle to impact the valve plate, so that it closes the oil circuit and the engine shuts down immediately. After this fault occurs, it should be eliminated by cleaning the solenoid valve, but the most important thing is to improve the cleanliness of the fuel, otherwise the fault will occur repeatedly.
2. Deformation and damage of the fuel injection pump rack
Why?
1）The fuel injection pump rack is stuck. Due to poor assembly or bending and deformation of the rack, the fuel injection pump rack is stuck, the fuel injection pump plunger cannot rotate, the fuel supply cannot be stopped, and the diesel engine cannot be turned off.
What to do?
At this time, the fuel injection pump should be disassembled for inspection and repair. If the fuel injection pump rack is bent and deformed, it can be straightened by knocking on the platform, but the surface must not be damaged; if the rack and gear mesh poorly, a small file can be used for local correction; if it is due to improper assembly of parts, it should be corrected.
Why?
2）The lug on the fuel pump rack falls off. The lug on the fuel pump rack of the diesel engine is welded on. If it falls off due to loose welding or excessive force, the throttle control handle will not be able to pull the fuel pump rack to move, and the fuel pump will not be able to change the oil volume, causing the diesel engine to fail to shut down.
What to do?
At this time, the fuel injection pump rack should be replaced or the lug should be re-welded. However, the repaired or replaced fuel injection pump rack must be able to mesh well with the adjustment gear and move flexibly.
3. Improper adjustment of the throttle control mechanism
Why?
When the vehicle's throttle control handle is in the maximum fuel supply position, the governor's outer lever control arm should collide with the high-speed limit screw, thereby limiting the maximum fuel supply and maximum speed. When the throttle control handle is pulled to the flameout position, the governor's outer lever control arm collides with the low-speed limit screw, causing the diesel engine to flameout. If the position of the high-speed limit screw and the low-speed limit screw is improperly adjusted, or the length of the governor's outer lever control arm is improperly adjusted, the throttle control handle has too small a stroke, and the throttle control handle has not yet been pulled to the position where the injection pump stops supplying fuel, the governor's outer lever control arm will collide with the low-speed limit screw, and the injection pump will continue to supply fuel, and the diesel engine will not be able to flameout.
What to do?
At this time, you should adjust the position of the low-speed limit screw or the length of the governor's outer lever operating arm so that when the injection pump is in the oil stop position, the low-speed limit screw collides with the governor's outer lever operating arm.
