The Adjustment And Structure Of The Valve Bridge Of The Diesel Engine

- Dec 02, 2017 -

Before adjusting the valve timing, attach a degree plate with 360°marks to the free end of the crankshaft and mount an adjustable pointer onto the timing gear case cover as a reference pointer when the crankshaft is turned.

 

Remove the cylinder head cover and turn the crankshaft until the timing pointer on the flywheel housing is pointing at the “0” mark on the rim of the flywheel. (Note: There are two punched marks on the timing mark inspection window of the flywheel housing for locating the timing pointer. For correct indication of timing, the timing pointer can not be distorted and its two sides must be located within these two punched marks.) With the crankshaft at this position, adjust the adjustable pointer mounted on the timing gear case cover to point at the “0” mark on the degree plate.

 

This indicates that the piston of the first and the sixth cylinders of the engine are at their top dead center position. To determine whether the first cylinder is at the beginning of its expansion stroke, remove the injection pump inspection door cover and check whether the plunger spring of the first pump elements is compressed or slightly bar the crankshaft and observe whether the intake and exhaust valves move. If the plunger spring of the first pump elements is compressed or if the intake and exhaust valves remain still when the crankshaft is slightly barred, it means the first cylinder is at the beginning of is expansion stroke. Then, adjust the valve lash.

 

To adjust valve lash, loosen the lock nut and valve lash adjusting screw on the rocker arm by means of a wrench and screw driver. Slip a feeler gauge between the rocker arm and the tip of the valve stem. Adjust the adjusting screw till the rocker arm just presses the feeler gauge against the valve stem tip and the feeler gauge can just be withdrawn by a slight pull. Then lock the adjusting screw with the lock nut, and check the valve lash again.

 

After adjusting the valve lash, valve timing can be checked. Usually, it is not necessary to check the valve timing. If necessary, begin with the 1st cylinder. While barring the crankshaft over, feel the movement of the push rod by turning it with fingers. As long as there is clearance between the rocker arm and the tip of the valve stem, the push rod of that valve is free to rotate. Thus, while the crankshaft is slowly bared in the direction of its rotation, the moment at which the push rod can just not be turned by hand is the moment at which the valve starts opening. Stop barring the crankshaft immediately and note the reading on the degree plate indicated by the reference pointer at the free end of the engine. This is the opening angle of that valve.

 

After taking the angle of opening, turn the crankshaft in the same direction until the push rod of that valve can just be rotated with fingers. This is the angle at which the valve just closes. Note the reading indicated by the reference pointer. Valve timing can thus be checked according to the ignition order of the engine. The specified valve timing is accordance with the range in technical parameter. If valve timing is incorrect due to wear of parts, it can be slightly compensated by varying the valve lash. Reducing the valve lash enables the valve to be opened earlier and closed latter. Increasing the valve lash gives the opposite results. But when doing such compensating adjustments, the valve lash must still be within the specified range.

 

Intake valve: Valve and rocker arm clearance under cold condition 4~0.45 mm.

 

Exhaust valve: Valve and rocker arm clearance under cold condition 0.5~0.55 mm.http://www.wandiengine.com/