Adjustment of Leakage Rate of PT Pump Throttle Valve in Cummins Generator

When the throttle is fully open, the fuel pressure flowing to the injector should reach the specified pressure, so that the maximum fuel injection volume meets the specified value; When the throttle is fully closed, use a limit screw to slightly open the oil passage and allow a small amount of fuel to flow through, which is called the throttle valve leakage position.

The leakage rate of the throttle valve of a 250kw Cummins generator is usually adjusted on the PT fuel pump test bench. If it is necessary to adjust the leakage rate of the throttle valve on the vehicle, the throttle valve connector must be adjusted to the position when the throttle valve is closed between the throttle valves (at this time, the throttle valve on the PT fuel pump is in contact with the stop screw of the front throttle valve), or the throttle valve must be fully opened to allow the diesel engine to operate at the highest no-load speed, The inspection should be completed using a stopwatch or other suitable timer and tachometer, and the steps are as follows:

1. Quickly release the throttle valve or move it to the closed position while pressing the stopwatch.

2. When the speed reaches 1000r/min, stop the stopwatch and pay attention to the deceleration time. Repeat the measurement several times and take the average value.

3. When the Cummins generator releases the accelerator pedal from the rated no-load speed and experiences stall (the idle speed governor cannot control the diesel engine), the leakage of the throttle valve must increase. This can be adjusted by tightening the throttle valve leakage adjustment screw (front throttle valve stop screw). The appropriate inspection method for adjusting is to increase the deceleration time (average value measured according to steps 1 and 2) by 1-2 seconds, lock the adjustment screw at this position, and recheck the idle speed. If necessary, readjust it.

4. When the deceleration time of the diesel engine is too long (relative to the average value), the leakage of the throttle valve should be reduced, which can be adjusted by unscrewing the adjustment screw for the leakage of the throttle valve. Before adjusting, it is also necessary to use a stopwatch to check the deceleration time from turning off the power key at high idle speed to stopping the diesel engine. If the measured time is greater than the average value measured in steps 1 and 2, it indicates that it is not a problem with the leakage of the throttle valve. If the measured deceleration time is significantly reduced, it indicates that there is a problem with the leakage of the throttle valve.

Generally speaking, excessive leakage control can cause slow deceleration of diesel engines; If the leakage is too small, the diesel engine will react slowly when the throttle is closed and then opened again. If the measured deceleration time is significantly shortened, it indicates that the leakage of the throttle valve needs to be reduced. Therefore, the throttle valve leakage speed control screw can be unscrewed, and the deceleration condition of the diesel engine can be checked using the method described above. If the diesel engine shows a tendency to stall after decelerating from high idle speed, the screw should be tightened again to increase the deceleration time by 1-2 seconds, and the adjustment screw should be locked in that position; Then, adjust the idle speed as needed.

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