Check And Adjustment Of Diesel Generator Engine

- Nov 10, 2017 -

(1)  Adjustment of injection timing

To ensure normal operation of the engine and to obtain the best economical fuel consumption and good combustion, injection timing should be checked and readjusted after every 500 operating hours and whenever the engine has been dismantled and reassembled.

To adjust injection timing, remove the high pressure fuel piping of the first cylinder and turn the crankshaft until the piston of the first cylinder is at the beginning of its expansion stroke. (To determine whether it is at the beginning of its expansion stroke, turn the crankshaft slightly and observe the movement of the valves. If the valves remain still when the crankshaft is slightly turned, it indicates that the first cylinder is at the beginning of its expansion stroke. ) Check the timing pointer on the flywheel housing which should point at the “0” mark on the rim of the flywheel. At this position, the plunger spring of the first pump element of the injection pump should be compressed. (This can be checked by removing the B-type injection pump inspection door cover.) Then turn the crankshaft in the direction opposite to that of its rotation about 40°. After this, turn the crankshaft slowly and smoothly in the direction of its rotation and observe the fuel level in the fuel outlet of the delivery valve holder of the first pump element at the same time. When this fuel level just starts to rise, stop turning the crankshaft immediately. This is the beginning of injection of the first cylinder whose angle can be read out from the degree marking on the flywheel rim at which the timing pointer points. The angle at which injection begins should be at the range of technical parameter of the relevant model diesel engine. If it is not within this limit, it can be adjusted by loosening the two screws(Fig.1 item C)on the injection pump coupling and turn the crankshaft till the coupling has turned the required angle. After adjustment, tighten the two screws and check the injection timing again.

Another way to adjust the injection timing is to turn the injection pump coupling. Turn the crankshaft until the piston of the first cylinder is at the beginning of its expansion stroke. Then turn the crankshaft in the direction opposite to that of its rotation till the timing pointer on the flywheel housing is relevant mark. Remove the injection pump inspection door cover and loosen the two screws on the injection pump coupling. Turn the injection pump camshaft in the direction of its rotation till fuel level in fuel outlet of the delivery valve holder of the first pump element just stars to rise. Then tighten the coupling screws and check the beginning of injection again. The beginning of injection should also be within the range of technical parameter of the relevant model diesel engine.

 

(2)  Adjustment of valve lash

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.

 

① Adjustment of 12V model diesel engine

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. With the crankshaft at this position, valve lash of the valve listed in the following table can be adjusted:

Table.1  When the 1st cylinder of the 12V model engine are at the beginning of their expansion stroke, valve lash of the following valves can be adjusted.

Cyl. No.

1

2

3

4

5

6

Valves can be adjusted

intake, exhaust

intake

exhaust

intake

exhaust


Turn the crankshaft 75°in direction of its rotation and let the twelfth cylinder at the beginning of the expansion stroke. Valve lash of the following can be adjusted. 

Table.2  When the 12th cylinder of the 12-cylinder engine are at the beginning of their expansion stroke, valve lash of the following valves can be adjusted. 

Cyl. No.

7

8

9

10

11

12

Valves can be adjusted


exhaust

intake

exhaust

intake

exhaust, intake

 

Using the same method, make the 6th cylinder and the 7th cylinder at the beginning of their expansion stroke, At this time, intake and exhaust valve lash in table.3 and table.4 can be adjusted.

Table.3  When the 6th cylinder of the 12V-cylinder engine is at the beginning of their expansion stroke, valve lash of the following valves can be adjusted.

Cyl. No.

1

2

3

4

5

6

Valves can be adjusted


exhaust

intake

exhaust

intake

exhaust, intake

Table.4  When the 7th cylinder of the 12V-cylinder engine is at the beginning of their expansion stroke, valve lash of the following valves can be adjusted.

Cyl. No.

7

8

9

10

11

12

Valves can be adjusted

exhaust, intake

intake

exhaust

intake

exhaust


 

② Adjustment of 6-cylinder diesel engine

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. This indicates that the piston of the 1st and the 6th cylinders of the engine are at their top dead center position. To determine whether the 1st cylinder is at the beginning of its expansion stroke, remove the injection pump inspection door cover and check whether the plunger spring of the 1st 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.

After ensuring the beginning of the expansion stroke.

When the 1st cylinder of the 6-cylinder engine is at the beginning of their expansion stroke, valve lash of the following valves can be adjusted.

Intake valves:1-2-4

exhaust valves: 1-3-5

 

When the 6th cylinder of the 6-cylinder engine is at the beginning of their expansion stroke, valve lash of the following valves can be adjusted.

Intake valves: 3-5-6

exhaust valves: 2-4-6

 

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.

 

(3) Check of valve timing

After adjusting valve lash, valve timing can be checked. Usually, it is unnecessary to do. 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 for 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 for 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.

 

(4) Adjustment of lubricating oil pressure

    After diesel engine starts, the oil pressure should be higher than 49kPa at about 600r/min while it should be 245~392kPa at rated speed. If the oil pressure doesn’t conform to above regulation, adjust it in time. When adjusting, unscrew the oil sealing nut on the pressure regulating value, loosen the lock nut, and then turn the adjusting bolt with a screwdriver. Screwing the adjusting bolt in or out will raise or lower the oil pressure respectively. After adjusting, the lock nut and oil sealing nut should be tightened in sequence.

 

(5) Adjustment of V-belt tension

During engine operation, the rubber V-belt must be kept at a proper tension. In the normal case, the V-belt can be pressed down 10~20mm when a 29~49N is applied to the midway of the  V-belt. If the belt is too tight, it will cause excessive wear of the bearings on the charging alternator, fan and water pump. But if the belt is too loose, it will cause the speed of the driven accessories to be lower than required, lowering the voltage of the charging alternator, cooling efficiency of the fan and flow rate of water pump. Then it will affect normal operation of the engine. So the tension of the V-belt should be checked and adjusted periodically..

For 12V model engine, the tension of rubber V-belt is adjusted by changing the position of the shaft with the adjusting bolt of the fan rack.

For in-line 6 cylinder model engine, the tension of rubber V-belt is adjusted by changing the position of the alternator bracket. Fix the bracket again after it has been adjusted to a proper tension.

It is useful to prolong the V-belt’s service life if used correctly and tightened properly. They must be renewed immediately when stratified or can not be tightened to required tension because of excessive extension.

When purchasing or replacing the V-belt, make sure that the type and length of the new ones should be same as those of the original ones. If a group of two or more V-belts are used, these belts should approximately have the same length., otherwise the tensions of these belts will be unequal to each other and cause quick damage.