Adjustment of PT fuel injectors on diesel engines

1. Adjustment of the pressure exerted by the injector plunger on the cylinder head

The pressure exerted by the fuel injector plunger on the cylinder head should neither be too high nor too low: excessive pressure can cause deformation of the fuel injector drive components. The pressure was too low. At the end of the injection, the residual fuel in the conical cavity of the plunger and the cylinder head sintered and formed carbon deposits, causing the cylinder head to overheat and resulting in the detachment of the front end of the cylinder head. Therefore, adjustments must be made when installing the fuel injector.

1.1 Torque adjustment method

This method involves tightening the fuel injector adjustment screw to the specified torque to ensure the pressure exerted by the plunger on the cylinder head when it is placed.

1) Calibrate the timing mark. Put the cylinder in a decompression state, rotate the timing pulley in the direction of the crankshaft's rotation, and align the timing marks on the pulley with those on the gear housing cover. The pulley mark TC indicates that the piston is at the top dead center position, and VS indicates that the piston is 90° behind the top dead center position. The numbers before the TC and VS marks are the corresponding cylinder numbers. After aligning the marks, determine the compressed cylinder based on the status of the intake and exhaust valves. Only one cylinder can be adjusted for each mark.

2) Adjustment. When the engine is cold, loosen the lock nut on the fuel injector rocker arm, screw in the adjusting screw to make the plunger move down. After the lower end of the plunger contacts the conical seat at the cylinder head, screw in the screw by 15° to squeeze out the remaining fuel at the cylinder head. Loosen the adjusting screw by one turn, then tighten it to the specified torque with a torque wrench. Keep the adjusting screw in position with a screwdriver and tighten the lock nut to the specified torque.

3) Re-examination. After all the fuel injectors have been adjusted, start the diesel engine. When the engine oil temperature reaches 60℃, check it again.

1.2 Travel adjustment Method

This method involves using a dial indicator and a rocker arm pressure rod to adjust the fuel injector plunger to the specified value.

Fix the dial indicator bracket on the cylinder head, with the measuring rod of the gauge vertically pressing against the flange surface of the fuel injector plunger. When the plunger is at the lowest position in contact with the cylinder head seat surface, adjust the dial indicator reading to zero. Rotate the crankshaft in the direction of the diesel engine's rotation to raise the plunger to the highest position. At this point, the reading on the dial indicator represents the plunger's stroke. If it does not meet the requirements, adjust the adjusting screw on the rocker arm to meet the requirements.

2. Inspection and adjustment of fuel injection timing

The inspection and adjustment of the fuel injection timing of the fuel injector are based on the interrelationship between the position of the piston and the position of the fuel injector push rod, and the fuel injection timing is adopted

The instrument was carried out.

2.1 Install the fuel injection timing instrument

First, remove the rocker arm cover, rocker arm assembly and fuel injector of one cylinder. Install the fuel injection timer. The timing instrument has two dial indicators: the dial indicator whose measuring rod is in contact with the piston is called the piston stroke dial indicator; The measuring rod of another dial indicator is placed against the push rod ball seat and is called the push rod stroke dial indicator. The installation position of the fuel injection timing instrument must be parallel to the center line of the cylinder.

2.2 Inspection and Adjustment

Turn the crankshaft clockwise to position the piston of one cylinder at the top dead center of the compression stroke. When the measuring rod of the piston stroke dial indicator's measuring head is aligned with the 90° scale line of the timing instrument, zero the push rod stroke dial indicator.

2) Rotate the crankshaft counterclockwise. When the top dead center mark of cylinders one and six is about 10mm away from the marking point of the scale, move the piston stroke dial indicator to compress the measuring head by about 5mm, and then fix it. Slowly rotate the crankshaft and zero the piston stroke dial indicator when the piston returns to the top dead center position.

3) Continue to rotate the crankshaft counterclockwise. When the measuring rod of the piston stroke dial indicator aligns with the 45° scale line on the scale (the corresponding crankshaft is 45° before the top dead center), rotate the crankshaft clockwise until the reading of the piston stroke dial indicator meets the specified requirements. Then, adjust the thickness of the tachometer pin cover gasket based on the measured difference to ensure that the fuel injection timing meets the specified requirements.