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PT Fuel System of Cummins Diesel Generator Set

Nov. 14, 2018

Installation and commissioning of Cummins generator set PT fuel system


Fuel pump commissioning


1. Preparation before commissioning. The fuel pump and fuel injector have been tested by the test bench. The diesel engine technology is in good condition and has entered the hot running state; the fuel pump and the drive unit are properly connected, the gear pump is injected with clean fuel; the throttle valve lever is disconnected from the connecting rod so that It can move freely; the tachometer is attached to the connecting device of the fuel pump chronograph drive shaft; check whether the instrument used (such as pressure gauge, tachometer, etc.) is normal.

PT Fuel System of Cummins Diesel Generator Set.jpg


2. Idle speed adjustment. Unscrew the screw plug from the cover of the PTG governor spring assembly. Adjust the idle speed (600 ± 20) r / min of the diesel engine by rotating the idle adjustment screw. After adjusting the idle speed, screw back the screw plug; the fuel pump equipped with the MVS governor, the idle speed adjusting screw is located on the governor cover, and after tightening the idler, tighten the lock nut to prevent air from entering.


3. High speed adjustment. Usually, when the fuel pump is commissioned by the test bench, no high-speed adjustment is required. If adjustment is needed, the method of increasing or decreasing the high-speed spring washer is still used; the speed of the governor breaking point should be 20~40r/min higher than the rated speed. In order to ensure that the governor will not play a limit before the calibration speed; the maximum idle speed of the diesel engine is generally higher than 10% of the rated speed.


Injector debugging work


1. Preparation before the test. The parts of the injector meet the technical requirements and are debugged by the test bench; the diesel engine is in good condition and enters the hot running state.


2. Plunger seating pressure adjustment. This adjustment can be carried out by the torque method. When the cold car is screwed into the rocker arm, the adjusting screw can move the plunger downward. After the plunger contacts the cone of the measuring chamber, it is screwed about 15 degrees to dissipate the fuel remaining on the seat surface. Squeeze, then loosen the adjusting screw one turn, then use the torque two handles to screw to the specified torque value, and tighten the lock nut; then perform the corrective adjustment according to the above method when hot.


3. Fuel injection timing adjustment. The timing of fuel injection is based on the relationship between the position of the piston and the position of the fuel insured, using a dedicated timing instrument. The fuel injection timing debugging step is to rotate the pulley so that the 1 and 6 cylinder pistons are at the top dead center, and the push rod stroke is when the measuring rod below the piston stroke dial measuring head is aligned with the 90 degree scale line of the timing gauge. The dial indicator is zero; turn the pulley counterclockwise, move the piston dial indicator when the 1 and 6 cylinder marks are turned to about 10 mm from the calibration point of the scale, and compress the measuring head by about 5 mm, then fix it. Then slowly rotate the pulley and zero the dial indicator when the piston stroke dial indicator is turned to the position where it was rotated clockwise. Continue to rotate the pulley counterclockwise. When the piston stroke gauge is below the measuring head and the ruler. When the 45-degree scale line is aligned, turn the pulley clockwise until the piston stroke dial gauge reaches the specified reading. Adjust the thickness of the swing-type tappet pin cover gasket according to the measured difference so that the injection timing meets the requirements.


In order to ensure the normal performance of the diesel engine technology, the fuel pump must be commissioned on the dedicated test bench according to the PT fuel pump calibration data. At present, the flow meter method is often used, and the specific test steps are as follows.


1. Install the fuel pump on the test bench. After the fuel pump is connected to the drive plate, fill the pump housing and the oil inlet of the gear pump with the clean test oil from the plug hole at the top of the fuel pump. Connect the oil inlet rubber hose and the cooling drain valve hose; check whether the regulator is stable to ensure the gear pump works stably; adjust the pointer of each measuring instrument to zero.


2. The idle speed small hole valve, the throttle valve and the leakage valve on the test bench are closed, and the vacuum regulating valve, the oil shutoff valve and the flow regulating valve are fully opened. The throttle valve of the fuel pump is in the fully open position, and the two-arm lever of the MVS governor is in contact with the high speed limit screw. The motor is started to allow the fuel pump to be commissioned at 500 rpm. If the fuel pump does not absorb oil, check whether the valve in the oil inlet line is open, whether there is air leakage, or the direction of rotation of the fuel pump is reversed; test operation for more than 5 minutes, let the air discharge from the oil, the oil temperature rises to 32-38 ° C.


3. Check the tightness of the fuel pump. At 500 rpm, open the flow adjustment valve, close the vacuum adjustment valve, the vacuum gauge reading should be 40KPA, apply a small amount of light grease to the vent hole of the fuel pump front cover spindle seal , if not inhaled, it means good sealing; check the O-ring of the throttle valve, the chronograph seal ring hole, the MVS governor double-arm lever shaft and the adjusting screw, the gasket between the gear pump and the housing, etc. Sex. Observing the air bubbles in the flow meter just indicates that some of the air has entered the fuel pump.


4. Adjust the vacuum. The flow regulating valve on the test bench is fully opened, the fuel pump is operated at the rated speed of the diesel engine, and the vacuum regulating valve is adjusted to make the vacuum gauge read 27KPA.


5. Adjust the flow meter. The fuel pump is operated at the rated speed of the diesel engine, and the flow regulating valve is adjusted to adjust the float of the flow meter to a prescribed value.


6. Adjust the speed at which the governor is disconnected. The throttle valve is fully open, and the fuel pump speed is increased until the fuel pressure begins to decrease. Check whether the fuel pump opening point speed is within the specified value. If it is lower than the specified value, a gasket can be added between the adjusting spring and the snap ring; otherwise, the gasket should be taken out. When equipped with the MVS governor, just use the high speed limit screw adjustment.


7. Check the fuel pressure point. Increase the fuel pump speed. When the fuel pressure drops to 276KPA, check if the fuel pump speed is within the specified range. The fuel pump speed will continue to rise and its fuel pressure should be reduced to zero. Otherwise, the fuel short circuit in the fuel pump is indicated.


8. Commissioning of the fuel outlet pressure at the rated speed and maximum torque point speed. Starting from zero fuel pressure, reduce the fuel pump speed to the rated speed and check if the fuel outlet pressure meets the specified value. When the MVS governor is not installed, use the increase or decrease of the gasket to adjust. When the MVS governor is installed, adjust the screw with the rotary throttle valve. When the fuel pump speed drops to the maximum torque point speed, check if the fuel outlet pressure meets the specified value. It can be adjusted by changing the amount of boosting plunger, that is, increasing the gasket of the low-speed torque correction spring to increase the fuel pressure, and vice versa.


9. The fly hammer assists in the inspection of the pressure. Run the fuel pump at 800 rpm to check that the fuel outlet pressure meets the specified value. The adjustment method is also to use a gasket that increases or decreases the low speed torque correction spring. It should be noted that the adjustment of the above items 4-8 is required after the thickness of the gasket is changed.


10. Adjustment of idle speed and fuel outlet pressure. The throttle valve, the leakage valve and the flow regulating valve on the PT pump test bench open the idle small orifice valve to make the fuel pump throttle shaft idle at the idle position, so that the fuel pump runs at an idle speed and check whether the fuel outlet pressure meets the specified value. It can be adjusted with the idle adjustment screw.


11. Check the amount of leakage of the throttle valve. The flow regulating valve and the idle small orifice valve on the PT fuel pump test bench are closed, and the throttle valve and the leakage valve are opened. When the throttle valve is in the idle position, the fuel flows into the measuring cup, and the leakage amount should meet the specified value. The PTG governor uses a front limit screw to tighten the throttle to adjust the amount of leakage, while the MVS governor is adjusted by increasing or decreasing the leakage adjustment pad on the outside of the idle spring seat.


After repeating the inspection and adjustment of the above items 3-11, seal the throttle valve limit screw of the PT fuel pump, the high speed limit screw of the MVS governor, and the chronograph.



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