Diesel PT fuel pump on the car adjustment method

Cummins N and NH series diesel engines are used PT fuel system, the series has two types: First, PT-G-type pump, governor - controller, the second is the PT-R-type pump, the Department of pressure - regulation.

The main features of the PT pump fuel system are: In the PT fuel system at Bosch, high pressure fuel is produced, the timing distribution and fuel quantity regulation are carried out in the fuel pump; in the fuel pump and injector fuel system, the fuel generates high pressure, Timing distribution and fuel volume control in the fuel pump and injector, the fuel into the injector only about 20% from the injector into the combustion chamber, the remaining fuel on the injector after cooling and lubrication return tank. Because the PT fuel system, the fuel pump output only low-pressure oil without high-pressure tubing, high-speed pressure wave does not exist under the pressure, and injector plunger down fast, small hole size, and thus injection pressure up to 100MPa, This is conducive to fuel atomization, full combustion, sewage and economy; diesel parking is the use of oil shut-off valve to cut off oil flow.

Diesel engine PT fuel pump on the car to adjust depends on the state of the diesel engine, parasitic load and the accuracy of the instruments used, the speed of its different conditions and adjust the inspection methods are as follows:

1, idle speed

With the diesel engine running, remove all air from the oil circuit and allow the diesel engine to reach its operating temperature. Unscrew the screw plug under the cover of the PT-G two-stage governor spring assembly. Adjust the idle speed and screw the adjusting screw at idle Increase the speed, screw out the adjustment screw idle speed is reduced; after the idle speed is adjusted, replace the screw plug.

On a PT fuel pump fitted with an MVS full speed governor, the highest speed and idle adjustment screw is located on the governor cover and tighten the lock nut immediately to prevent air from entering the fuel pump.

For each series of diesel engines, the factory has a recommended idle speed, the speed allows a reasonable change, if it is too large, it is difficult to hang gear, if too low, it is easy to turn off.

If the idle speed instability, which with the governor plunger, should check the fly hammer boost plunger out of volume.

2, the maximum speed (accelerator pedal in the end)

The maximum speed is usually calibrated on a PT fuel pump test rig, generally using a method of increasing or decreasing the governor high speed spring washer; if it has been adjusted on the test rig, it does not need to be changed.

The highest no-load speed on the car check method is: the transmission in neutral or clutch in the open state, open the throttle and keep the fully open position, then the maximum speed of the diesel engine than the governor off point speed of 10% -12%; When this speed greatly exceeds the specified value, governor components should be checked for failure or check whether the parts are suitable.

3, governor off point speed

When the throttle is fully open, increase the load until the speed drops to at least 100 rpm less than the rated speed, and then gradually reduce the load while observing the fuel outlet pressure gauge (as the load decreases, the fuel outlet pressure will increase until The speed limiter starts to limit the oil supply, and then the fuel outlet pressure will begin to decrease as the load decreases.) This is the governor disconnect point, which will not have a limit before the rated speed of the diesel engine (such as the diesel engine speed 2100r / min, the governor off point speed of 2120-2140r / min). If the governor disconnect point speed is higher or lower than the specified value, the shim may be reduced or increased from the back of the governor high speed spring accordingly until the governor break point rotational speed meets the specified value .

4, fuel export pressure

Method one: Diesel engine and dynamometer load, first check the governor off point speed, the throttle fully open, increase the load to the diesel engine rated speed, and observe the fuel outlet pressure. When the pressure is lower or higher than the limit value, adjust as follows: Unscrew the maximum throttle opening adjustment screw, remove the throttle shaft and apply the appropriate thickness of the gasket to increase the pressure from the throttle Remove the appropriate thickness of the gasket, can reduce the pressure. Under no circumstances should the PT fuel pump's fuel outlet pressure be adjusted beyond the maximum rating.

Method 2: When the throttle is fully open, check the maximum pressure of the fuel outlet through the transmission from low speed to high speed. If the pressure is lower than the minimum value specified by the aircraft or higher than the specified maximum value, it shall be adjusted according to method one.
Method 3: also known as "instantaneous" pressure test method; this method is not as accurate as method one or two, but relatively simple, that is, unscrew the solenoid valve off the oil and install the pressure gauge, remove the throttle valve rocker arm (throttle rocker arm) On the connector, the throttle arm clockwise fully; start the diesel engine and make it higher than the idle speed 250r / min speed; then quickly accelerated to the maximum speed of the diesel engine, and check the pressure gauge instantaneous pressure indication , The adjustment method as described in method one. After the inspection is completed, the pressure gauge should be removed, the fuel cut-off solenoid valve should be installed, and the pipe running through the smoke limiter should be blocked.

5, throttle leakage

When the throttle is fully open, the pressure of the fuel flowing to the injector should reach the prescribed pressure so that the maximum fuel injection quantity meets the stipulated value. When the throttle is fully closed, the trap oil is used to slightly open the oil passage to allow a small amount of fuel to flow through. This part of the fuel is called throttle leakage. Throttle leakage of large, can cause slow deceleration woodcut machine, the leakage is too small, it will open the throttle closed and cause slow reaction of the diesel engine.

The amount of throttle leakage is usually adjusted on the PT fuel pump test bench. If it is necessary to adjust the throttle leaking amount on the vehicle, the throttle valve connection must be adjusted to the position at which the throttle is closed (in this case, the PT fuel pump On the throttle just before the throttle valve stopper screw contact), or the throttle valve fully open, so that the diesel engine to run at the highest no-load speed, check with a stopwatch or other suitable timer and tachometer to complete, The steps are as follows:

(1) Release the throttle valve quickly or move the throttle valve to the closed position while pressing the stopwatch.

(2) When the diesel engine reaches 1000r / min, stop the stopwatch and note the deceleration time, and repeat the test several times, whichever is the average.

(3) Stall (idling governor can not control diesel engine) occurs when the diesel engine loosens the accelerator pedal from the rated no-load speed and the phenomenon that the throttle valve leakage amount must be increased can be adjusted by screwing in the throttle valve leakage amount Adjust the screw (front throttle stop screw). Whether to adjust the appropriate inspection method is: deceleration time (measured in accordance with the average value of steps 1 and 2) should be increased 1-2S, in which position the adjustment screw locking, and re-check the idle speed, if necessary, readjust.

(4) When the diesel engine decelerates for a long time (relative to the average value), reduce the throttle leakage and adjust it by unscrewing the throttle leakage adjustment screw. Before adjustment, the need to stop using the stopwatch at high speed no-load speed to open the door to the diesel engine parking deceleration time, if the measured time is greater than the average measured in accordance with steps 1, 2, not throttle leakage The amount of questions. If the measured deceleration time is greatly reduced, indicating the amount of throttle leakage. If the measured deceleration time is greatly reduced, indicating the throttle leakage to be reduced, for which, you can screw out the throttle leakage rate control screw, while checking the deceleration of the diesel engine as described above, if the diesel engine speed from no-load speed After another stalls to heat, then the screw should be screwed in, so that the deceleration time increase 1-2S, and in this position the adjustment screw locking; then, if necessary, speed control idle speed.

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