There are three methods of injector injection stroke adjustment of Cummins diesel engine PT fuel system, the traditional method is the stroke measurement adjustment method (hereinafter referred to as the stroke method) and the torque adjustment method (referred to as the torque method), using these two methods to adjust, not only need to use special instruments, but also when adjusting on diesel engines with a long running time, its accuracy is not ideal.
Here we recommend a new adjustment method – angle method.
Cummins diesel engine injection stroke adjustment is very important, it directly affects the performance of the diesel engine, inaccurate adjustment one by one stroke is too large or too small (see Figure 1, that is, the size of the extrusion force of the injector plunger 29 to the bottom of the injector 14) will have a negative impact on the diesel engine, such as abnormal operation, power drop, or even failure to operate.
The specific performance is as follows:
Too large a stroke (i.e., the extrusion force of the injector plunger 29 to the bottom of the injector 14 is too small or there is a gap between them) will cause the injector 14 nozzle hole to be blocked.
When the plunger 29 is down, the bottom of the injector 14 cannot be fully squeezed, so that the diesel remaining in the injector 14 and its nozzle cannot be completely sprayed out, and the diesel combustion entering the cylinder produces high temperature and high pressure gas, which will go against the nozzle hole, so that the diesel fuel in the nozzle hole is not fully heated and burned to produce carbon deposits, and over time the nozzle hole will be partially or completely blocked.
The stroke is too small, that is, the plunger is too squeezing force on the bottom of the injector) will cause the injector 14 to be damaged or even crushed.
If the injection stroke adjustment is too small, the extrusion force of the plunger 29 to the bottom of the injector 14 is too large, the plunger 29 will squeeze the injector 14 or the bottom nozzle part of the injector 14, causing the sealing surface of the bottom of the injector 14 to be damaged or the top of the nozzle part of the injector 14 is damaged, and the top broken metal falls into the cylinder, which will cause the diesel engine to seriously knock on the cylinder, and even damage the piston, cylinder head and cylinder liner.
This phenomenon occurs when adjustments are made using the stroke method or the torque method.
Why is it easy to cause the oil injection stroke to be too large or too small?
The main reasons are as follows:
(1) When using the stroke method for adjustment, the main reason is that the wear of the fuel injection camshaft is uneven.
Refer to Figure 2, the contour wear of the cam is uneven under normal circumstances, the pressure between the protruding part and the roller 17 (Fig. 1) is larger, and the recessed part is smaller, so the wear degree of the concave part relative to the recessed part is also larger, on the contrary, the concave part is less wearing, the diesel engine after a long period of operation, the injection stroke provided by the fuel injection cam is smaller than that of the new diesel engine, and the adjustment stroke of the stroke adjustment method is stipulated. In this way, adjusting the diesel engine after running for a long time according to the specified amount of stroke will reduce the fuel injection stroke relatively, which will cause the carbon accumulation and blockage of the fuel injector 14 nozzle hole.
(2) When using the torque method for adjustment, the difference in tightness of the adjustment screw and the lock nut and the difference in spring elasticity when the adjustment screw twists on the rocker arm are mainly not considered.
The tightness of the adjustment screw is different each time it is adjusted, and the torque of the lock nut in the adjustment process of each injector is also different, and the cleanliness of the adjustment screw and the lock nut during assembly is not exactly the same, so when the adjustment screw is twisted on the rocker arm, its tightness is different, so when adjusting by the torque method, although the torque data used is the same, the degree of compression of each plunger on the bottom of its injector 14 is different, some are tight, some are loose.
In this way, for each plunger, the degree of compression of the plunger to the bottom of the injector 14 will not be exactly the same many times, and some will still be tight and some will be loose.
How can the injection stroke of the injector be accurately adjusted?
A new method is recommended here: the angle method.
The angle method is a method of adjusting the injection stroke by screwing the adjustment screw 27 into the plunger 29 just touching the bottom of the injector 14, and then screwing the adjustment screw 27 clockwise at a certain angle (see Fig. 1).
The specific steps are as follows (see Figure 3):
(1) Use torx wrench 1 to loosen the lock nut 2,4~5 turns (Figure 3).
(2) Loosen the adjustment screw with a flathead screwdriver 3,1~2 turns (Figure 3).
(3) Find the fuel injector that needs to be adjusted, turn the crankshaft to align the pulley with the timing mark, make the 1-cylinder intake and exhaust valve fully closed (that is, the intake and exhaust valve rocker arm is loose), and then adjust the stroke of the 1-cylinder injector.
(4) Put the screwdriver on the loosened adjustment screw 3, slowly screw into the adjustment screw 3 with one hand (Fig. 3), and stop immediately when it feels suddenly pushed (at this time, the plunger has just touched the bottom of the injector 14, see Fig. 1).
(5) Do not screw the torx twelve-angle wrench on the lock nut 2., remember to adjust the direction of the screwdriver inserted into the notch at the upper end of the tack 3 and align with the part of the torx wrench 1.
(6) Keep Torx wrench 1 still, and adjust screw 3 clockwise to twist a torx angle, which is 30 degrees.
(7) Repeat (2) . (4) . (5) . (6) One to three times to ensure accurate adjustment.
(8) Adjust the screw 3 and fix it, tighten the lock nut 2.
(9) Repeat 1~8 and press (1). (5). (3). (6). (2). (4) refer to the order of A. B. Mark C adjusts each injector of the diesel engine in turn (for other multi-cylinder engines, the corresponding cylinder can be adjusted according to its firing order).
The adjustment of the angle method avoids the disadvantages of the stroke method and the torque method by fixing the value, and directly adjusts the rotation angle of the adjustment screw after the plunger just touches the bottom of the injector 14, which is essentially directly adjusting the extrusion degree of the injector plunger and the bottom of the injector 14, which greatly reduces the adjustment error caused by various reasons.
However, due to the fact that all manual adjustments do not require any special tools, the adjuster needs to have certain maintenance experience to make accurate adjustments.
After testing on site, after 2,000 hours of operation of the diesel engine adjusted by this method, the engine works normally, and the fuel injector is removed for inspection, and no blockage of the fuel injection hole is found.
