How to adjust the valve clearance of Mitsubishi eight-cylinder diesel engine in Japan

1. Adjust the crankshaft with secondary positioning method Ⅱ Ⅲ ⅴ.

This method can adjust all valve clearances only by turning the crankshaft twice, that is, finding two fixed positions of the crankshaft. The specific method is as follows:

(1) Turn the crankshaft until the two valves of the first cylinder overlap (at this time, the two valves act at the same time, that is, the exhaust valve is about to close and the intake valve is about to open), and stop shaking. This is the crankshaft position Ⅰ. Fig. 1 is the schematic diagram of twice positioning and adjusting the crankshaft valve of FL4 13 diesel engine, and fig. 2 is the schematic diagram of twice positioning and adjusting the crankshaft valve of FL9 12 diesel engine. At this point, the valve shown in black can be adjusted.

(2) After all valves at crankshaft position I are adjusted, continue to rotate the crankshaft for 360℃, that is, crankshaft position 2. With the mark on the V-belt pulley or flywheel, you can confirm that the crankshaft has just turned 360℃ and all other valves can be adjusted in position 2. To prevent confusion, you can mark the valve that is adjusted for the first time.

(3) Valve clearance adjustment: According to the specified value of the valve with adjustable crankshaft position, insert the feeler gauge into the rocker head and the tail end of the valve stem, whichever can be pulled lightly. If the clearance is too large or too small, loosen the lock nut, turn the adjusting screw until the clearance of the feeler gauge is appropriate, and finally lock the nut.

When the valve is adjusted by the crankshaft twice positioning method, the crankshaft is rotated less times and the adjustment is simple. All valves can be adjusted only by turning the crankshaft twice, but the maintenance personnel are required to memorize the order of adjusting the valves with crankshaft one and crankshaft two, and there are many valves, so it is easy for unfamiliar people to mix vegetables.

2. Adjust according to the ignition sequence.

This method is to rotate the crankshaft several times according to the ignition sequence of the engine, so that the valves of each cylinder overlap.

Adjust the valve lash of the corresponding cylinder. Using this method to adjust the valve clearance is actually to find the fixed position of each cylinder during valve adjustment. The method is as follows:

When the crankshaft rotates to the position where the two valves of cylinder I overlap (that is, the exhaust valve has not been completely closed and the intake valve has just opened), check the gap between the intake valve and the exhaust valve of the corresponding adjustable cylinder with a feeler gauge. If it is unqualified, send the locking nut with a wrench, then turn the adjusting screw with a screwdriver, and tighten the nut with a wrench after adjustment. The adjustment method of other cylinders is the same as that of cylinder I. The attached table gives the ignition sequence and valve clearance adjustment sequence of various vehicles, where "B" is the overlapping valve and "A" is the corresponding adjustment valve. For example, in a diesel engine of model F 12L4 13, when the crankshaft rotates until the valves of cylinder I overlap, the corresponding intake valve and exhaust valve of cylinder VI are adjusted, and then when the crankshaft rotates until the valves of cylinder VIII overlap, the corresponding cylinder to be adjusted is cylinder VIII. When the engine ignition sequence is used to adjust the valve clearance, the crankshaft rotates many times, so that the intake valve and exhaust valve of a single cylinder can be adjusted at the same time, and the adjusted valve is more accurate. Maintenance personnel need to memorize the ignition sequence of the engine and the valves of the adjustable cylinders corresponding to the valves of each cylinder, but it is very troublesome to turn the crankshaft to find the overlapping valves of each cylinder and the corresponding cylinder.

3. Adjust the valve clearance according to the injection timing

This method is to adjust the valve clearance of the engine during single-cylinder fuel injection. Firstly, disassemble the high-pressure fuel pipe of the engine fuel injection pump into the injectors of each cylinder, rotate the crankshaft, and observe the oil outlet of the high-pressure fuel pipe of each cylinder. When you see oil coming out of the high-pressure oil pipe of a cylinder, stop rotating, which means that the piston of this cylinder is running to the top dead center of this cylinder, and the intake and exhaust valves are completely closed. Open the valve cover and adjust the intake valve and exhaust valve of the cylinder. After adjustment, continue to rotate the crankshaft, observe the oil output of the high-pressure fuel pipe of the injector of other cylinders, and adjust the valves of other cylinders.

It is a simple method to adjust the valve clearance by using injection timing, and it is not necessary to remember the ignition sequence. When the high-pressure oil pipe of the fuel injection pump produces engine oil, the valve of the cylinder can be adjusted.