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YC4108D and YC4108ZD Yuchai Diesel Engine Generator Adjustment

Nov. 28, 2017

Below is the part three of Yuchai YC4108D-and-YC4108ZD series diesel engine generator operation and maitenance manual. The main steps include fuel supply advance angle adjustment, valve clearance adjustment, fuel injection presure adjustmentand oil pressure adjustment.

I Fuel Supply Advance Angle Adjustment

adjustments for the flange of fuel injection of pump

a. adjustments for the flange of fuel injection of pump


 adjustment for the shaft of fuel injection of pump

b. adjustment for the shaft of fuel injection of pump

Technical data : Static fuel supply advance angle is 14 ±2℃ A before TDC.


Fuel supply advance angle check: Unscrew the nut which connect the high pressure fuel line for the No.1 cylinder and fuel injection pump, crank the crankshaft slowly until the fuel level in the delivery valve holder begins to fluctuate. At this time, the timing value indicated by the pointer on the gear housing and the dial on the belt pulley damper is the fuel supply advance angle.


Fuel supply advance angle adjustment: There are three rectangle slots in the joint flange of the fuel injection pump, through which three bolts are used to fasten the fuel injection pump to the gear housing. After unscrewing these bolts, the fuel injection pump can be rotated around its axis with small angle in order to adjust properly the fuel supply advance angle. Crank the crankshaft to the position at which the fuel will be delivered  to the No. 1 cylinder according to the above method, unscrew these bolts on the flange and all the joint nuts for the high pressure fuel lines, rotate the pump a certain angle as required (inner direction which means to increase the fuel supply advance angle, outer direction which means to decrease the fuel supply advance angle) , then fasten the bolts on the flange. Check and adjust the fuel supply advance angle to prescription, then fasten the bolts- on the flange.


If the bolts is adjusted to the dead position on the rectangle slots in the flange and the fuel supply advance angle still does not meet the prescription, remove the gear housing cover plate of the fuel injection pump unscrew the three bolts used to fasten the gear of the fuel injection pump rotate the pump (inner direction which means to decrease the fuel supply advance angle, outer direction which means to increase the fuel supply advance angle). At last fasten the bolts. Check and adjust the fuel supply advance angle to prescription according to the above method, then recheck whether the bolts are fastened and install the gear housing cover plate. Pay attention to not damaging the gasket during adjustment in order to avoid the fuel leakage.

II Adjustment Of The Valve Clearance

 adjustment of the valve clearance

adjustment of the valve clearance


Technique demand ( cold state) : 0.4-0.05 mm

Intake valve clearance: 0.4±0.05mm

Exhaust valve clearance: 0.45±0.05mm


To determine the compression TDC of the first cylinder: Rotate the crankshaft to make the TDC indicator, which is mounted on the gear house cover, point to the "O" position on the belt pulley damper. Then go on rotating in a small range of angles (100 ~200) clockwise and counterclockwise. When the intake and exhaust rockers of the first cylinder do not swing but those of the forth cylinder swing, rotate the crankshaft hack to make the indicator point to the "O" position. At this time, the piston of the first cylinder is on the compression TDC. If counter, that indicates the forth piston is on the compression TDC. The first piston can reach the compression TDC by rotating the crankshaft 360.


To adjust valve clearance: Rotate the crankshaft to the position that the first piston is on the compression TDC, when the No. 1,2,3 and 6 valves can be adjusted; and then rotate the crankshaft 3600, when the No. 4, 5, 7 and 8 valves can be adjusted. First, loose the tightening nut of the adjustment bolt and screw the adjustment bolt out to the suitable position, Then put the feeler gauge into the gap between rocker and the end of valve stem. Next screw in the adjustment bolt till rocker can fasten feeler gauge. Finally, tighten the tightening nut. A correct valve clearance should he able to allow the feeler gauge move with slight resistance.

III Fuel Injection Pressure Adjustment

Technique demand

Fuel injection pressure 23±0.5MPa

26±0.5MPa (turbo charge)


fuel injection pressure adjustment

fuel injection pressure adjustment


Fuel injection pressure adjustment: Remove the pressure - adjusting screw thimble, screw in or out the pressure -adjusting screw as required. Screwing in means the increase of the injection pressure, on the contrary, screwing out means the decrease of the injection pressure. The fuel injection pressure can be adjusted on special test rig.

IV Oil Pressure Adjustment

Oil pressure adjustment

Oil pressure adjustment

Technical data : Oil pressure at idle speed≥ 0.1MPa

Oil pressure at rated speed: 0. 25 ~ 0, 6MPa

Oil pressure adjustment: The,oil pressure can be adjusted by the adjusting; screw of relief valve on the oil filter. During adjustment, remove the nut on the relief valve, unscrew the locking nut, screw in the adjusting screw with screwdriver, then the oil pressure will be increased.  If the adjusting screw is screwed out, the oil pressure will decrease. After the adjustment fasten the locking nut and nut. If the adjusted oil pressure does not meet the requirement, check the trouble in the oil passages carefully and troubleshoot them.

For more Yuchai YC4108D/YC4108ZD user manual information:

Diesel Engine Main Installing Requirements

YC4108D/YC4108ZD Series Diesel Engine Cautions


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