Usage:
The fuel system consists of the injection pump assembly (injection pump proper, governor, feed pump), auto timer, fuel filter, injection nozzle, injection pipe, and other parts.
Fuel is fed from the fuel tank through suction pipe to the feed pump of the injection pump assembly, and then to the fuel filter, injection pump, and injection nozzle. The excess fuel is returned from the injection pump to fuel tank (direct injection type engine) or from the injection nozzle to the fuel tank (swirl chamber type engine).
(1) A-type Injection Pump
The injection pump is a device which forces fuel to the injection nozzle and has a mechanism for increasing or decreasing the pressure feed quantity according to the engine load and speed.
The injection pump is constructed as shown in illustration at right. It has one plunger and delivery valve for each cylinder.
The plunger, pushed up by the camshaft and pushed back by the plunger spring, moves up and down through the plunger barrel on a predetermined stroke to feed fuel under pressure.
Both ends of the camshaft is supported by the taper roller bearings and is driven by the timing gear at 1/2 engine speed.
(a) Pressure feed of fuel
The plunger has an obliquely cut groove (lead) on its side as shown. At the top of the plunger there is a hole which leads to the groove. The plunger barrel has suction and discharge ports.
The fuel delivered to the injection pump is forced by the rotation of the camshaft or reciprocating motion of the plunger as shown below.
When the plunger is at the lowest position or bottom dead center (a), fuel flows through the suction and discharge ports into the plunger.
Rotation of the camshaft moves the plunger up. When the top surface of the plunger is lined up with the suction and discharge ports, application of pressure to fuel begins (b).
As the plunger moves up further (c), and the lead of the plunger meets with the suction and discharge ports, the high pressure fuel flows through the hole in the plunger and runs back from the lead to the suction and discharge ports, and the pressure feed of fuel is completed (d).
The plunger stroke during which the fuel is fed under pressure is called the effective stroke.
(b) Injection amount control system
According to the engine load, the amount of injection is increased or reduced by turning the plunger a certain angle to change the position where the lead meets with the suction and discharge ports on the up stroke and increasing or reducing the effective stroke.
The control rack is coupled to the floating lever in the governor. If the control rack is moved to right or left by operation of the accelerator pedal or governor, the control sleeve in mesh with the rack is turned. Since the bottom of the control sleeve is in mesh with the bar of the plunger, the plunger turns with the control sleeve, so the effective stroke changes and the injection amount increases or decreases. The more the control rack is pulled toward the governor, the less the effective stroke and the less the injection amount.
Each plunger is in mesh with this single control rack and simultaneously turns the same amount.
(c) Delivery valve
The delivery valve, provided on the top of the pump housing, performs the function of discharging the pressure in the injection pump.
The fuel compressed to a high pressure by the plunger pushes the delivery valve up and spouts out. If the pressure feed stroke of the plunger ends, the delivery valve is brought back to its original position by the pressure of the delivery valve spring to block the fuel path, thereby preventing counter flow of the fuel.
The delivery valve is brought down further until the seat surface is held tight. During that stroke the fuel is drawn back from above to instantly lower the residual pressure between the delivery valve and nozzle. The draw-back effect improves the end break of an injection from the nozzle and prevents after-injection dripping.
A delivery valve stopper is provided on the top of the delivery valve spring. The stopper limits the lift of the delivery valve and prevents valve surging during high speed rotation. In addition, it reduces the dead volume between the delivery valve and nozzle, thereby stabilizing the injection amount.
(d) Overflow valve <4D31, 4D31-T>
When the fuel pressure in the injection pump exceeds a set level, the steel ball in the overflow valve goes up to let the fuel flow out of the injection pump and return to the fuel tank, thereby stabilizing the fuel temperature and temperature distribution in the injection pump and maintaining the injection rate into each cylinder constant.
(2) Governor
(a) RSV type governor
The RSV type governor is a centrifugal type all-speed governor coupled to the camshaft of the injection pump. The governor not only controls the maximum and minimum speeds but also automatically controls the engine speed at any intermediate speed position.
The governor, as shown, consists of flyweights mounted to the injection pump camshaft. When the flyweights turning on the flyweight supporting shaft open outward, the roller mounted to the end of flyweight arm pushes the end of the sleeve in the axial direction. The governor sleeve, being made integral with the shifter through a bearing, moves only in the axial direction.
The shifter, mounted to the guide lever hung on the supporting lever shaft of the governor cover, prevents rotation.
The floating lever is mounted to the middle of the guide lever by the shaft with the bottom end as the fulcrum, whereas the top of the lever is coupled through the shackle to the control rack.
The start spring, attached to the top end of the floating lever, always pulls the control rack in the direction that fuel is increased.
The turning shaft of the swivel lever is fitted into the bushing of the governor cover and its center is eccentric with respect to the mounting position of the governor spring installed to the tension lever. The governor spring is installed to the end of the swivel lever. When the governor spring receives tension, the bottom end of the tension lever touches the adjustable full-load stopper bolt.
When the angle of the adjusting lever is changed, the angle of the swivel lever is also changed and the tension of the governor spring changed. This is because the turning center of the swivel lever and the mounting position of the governor spring installed to the tension lever are eccentric to each other as mentioned above.
An adjusting screw is also mounted to the swivel lever. Adjustment of the screw changes the tension of the governor spring, thereby making it possible to adjust the speed regulation.
An Ungleich spring is provided in the bottom portion of the tension lever. Adjust the tension of the spring by adding or removing shims.
An idling sub spring adjustable from outside is provided in the middle of the governor cover. During idling, the spring always keeps in contact with the tension lever to maintain a constant idling speed.
The stop lever, mounted through the supporting lever to the bottom end of the floating lever, returns the control rack to the stop position with a slight pressure irrespective of the adjusting lever position.
1) Start of engine
When the adjusting lever is moved to the start position (until it touches the maximum speed stopper), the swivel lever which moves with the adjusting lever pulls the governor spring and moves the tension lever until it touches the full-load stopper bolt.
At that time, the flyweights are stationary, and the start spring with weak tension pulls the floating lever in the direction that fuel is increased.
At the same time, the shifter and governor sleeve push the flyweight roller to the left.
As the result, the tension lever and shifter are spaced that much apart, and the corresponding amount of fuel is supercharged to facilitate starting.
2) Idling control
Once the engine is started and the adjusting lever returned to the idling position, the tension of the governor spring is drastically reduced.
Now the flyweights can move outward even at a low speed, so the tension lever is pushed back until it touches the idling sub spring and places the control rack at the idling position. In this state, the centrifugal force of the flyweight and the weak-state governor spring and idling sub spring achieve balance and maintain smooth idling.
When the speed falls, the centrifugal force decreases, the flyweights move inward, and the idling sub spring pushes the tension lever to the left and moves the control rack in the direction that fuel is increased.
If the speed falls radically, the start spring with weak tension acts and moves the control rack in the direction that fuel is increased to maintain the idling speed.
3) Maximum speed control
When the adjusting lever is moved to the full-load position, the tension of the governor spring is increased and pulls the tension lever until it touches the full-load stopper bolt.
When the engine exceeds the specified speed, the centrifugal force of flyweights becomes larger than the force of the governor spring pulling the tension lever. So the tension lever is moved to the right and moves the control rack in the direction that fuel is reduced, thereby preventing the engine from exceeding the specified speed.
If the speed further increases, the centrifugal force of flyweight increases and pushes the tension lever to the right and also compresses the idling sub spring to pull the control rack back to the no-load maximum speed position, thereby preventing over-speed operation of the engine.
The RSV type governor controls the entire speed range from idling to maximum speed. If load increases or decreases at a certain speed determined by the position of the adjusting lever, the governor automatically functions and maintains the engine speed constant at all times.
4) Ungleich operation
The Ungleich device controls fuel injection in such a way as to match the engine performance (the required injection varies with engine speed).
The air intake rate of the engine falls as the engine speed increases. The injection pump, on the other hand, increases the per-stroke injection as the speed increases, even with the control rack at the same position.
Therefore, if full load is set at point A to derive enough output at low speeds, the injection will reach B as the speed increases, and the engine will produce black smoke.
If full load is set at point B' to prevent black smoke, the low speed injection will come down to A', allowing combustion of more fuel.
So the Ungleich device accomplishes the function of setting full load at point A to derive the largest possible torque in the low speed range, and changing it to adjust the injection to point B' in the high speed range.
When the engine speed is low and the centrifugal force of flyweight smaller than the set tension of the Ungleich spring, the shifter is moved as much as the Ungleich stroke to the left, so the control rack moves in the direction that fuel is increased to increase the torque of the engine at low speeds.
As the engine speed increases, the centrifugal force of flyweight increases. If it becomes larger than the set tension of the Ungleich spring, the Ungleich spring is slowly compressed before the start of high speed control, and the control rack moves in the direction that fuel is reduced. The Ungleich stroke is completed at the position where the shifter directly touches the tension lever.
5) Stopping of engine
When the stop lever is moved to the stop position, the control rack is moved to the stop position to stop the engine regardless of the position of the adjusting lever.
6) Operation of torque spring
Construction machinery engines are often subjected to a large load during operation, and reduced speeds often lead to stalls. To prevent this, a torque spring is provided.
When the adjusting lever is fixed in the lever set position, a sudden increase of load, if no torque spring is provided, will move the control rack along the B-D curve as the speed falls. The rotational displacement at the time may be expressed as P1.
If a torque spring is provided, the control rack moves along B-C, and the rotational displacement at the time may be expressed as P2. Therefore, large changes occur in P2 and engine speed, and because of increased fuel injection, the engine torque increases, and large combustion noise warns the operator of the increased load, enabling him to take proper action to prevent stopping the engine.
In an abrupt increase of load occurs when the engine is running at continuous rating, the engine speed falls. So the flyweights are moved inward and the tension lever pulled to left by the governor spring, causing the control rack to move in the direction that fuel is increased.
At the time, the tension lever pin pushes the bottom of the torque control lever, and the lever moves with the pin A as the fulcrum, whereas the portion B is pushed to right. As the result, the torque spring performs the function of reducing movement of the tension lever.
(b) RLD type governor <Option: 4D31-T>
The RLD governor is an all-speed governor providing smaller lever reaction.
1) Flyweights
The flyweight holder is mounted on the injection pump camshaft and the flyweights pivot about the pin press-fitted into the flyweight holder. When the flyweights move outward under centrifugal force, the sliders on their arm ends pushed the sleeve in the axial direction. The sleeve is connected via bearing to the shifter which is pinned directly to the bottom of the tension lever. So, the flyweights impart their motion through the shifter to the tension lever.
2) Link
The RLD governor link operates as follows to regulate and control all speeds.
Among the idling, governor, and start springs, only the start spring retains the initially set tension. So, the flyweights start to move out under the centrifugal force more than the set tension of start spring. They move further outward as the engine speed increases, and the motion is transmitted to the tension lever, gradually putting more tension on the idling and governor springs. The guide lever is moved integrally with the tension lever by the set tension of cancel spring A to displace the ball joint.
By placing the adjusting lever gradually from the idle to full position when the guide lever ball joint is located at Po with engine stationary, the supporting lever moves to cause the floating lever to pivot about Po. (The point Po is a fixed point since the guide lever moves integrally with the tension lever by the set tension of cancel spring A.) This causes the control rack to move from Ro in the direction of greater fuel delivery. When the rack reaches Ra, the full load position determined by the torque cam, Ra becomes fixed to stop the supporting lever at Qb.
When the adjusting lever is further moved, only the L lever moves, away from the supporting lever. Starting the engine under this condition increases the pump speed, allowing the flyweight centrifugal force to overcome the tension of idling and governor springs to move the tension and guide levers. As pump speed increases, Po moves to Pa and Qb to Qa by the cancel spring B tension. These movements continue until the L lever contacts the supporting lever at Qa.
When the flyweights move further outward as a result of increased pump speed, the guide lever ball joint moves from Pa to Pa'. This causes the floating lever to pivot about Qa, moving the control rack from Ra in the direction of smaller fuel delivery up to Ra'.
The governor can thus control the amount of fuel and engine speed by presetting the adjusting lever at any desired position.
The governor is so constructed as to allow the lever ratio to become greater as the flyweights move further outward.
When the governor controls idle speed with a low pump speed, the flyweight centrifugal force is small; under which conditions, the lever ratio is made smaller to ensure that the control rack moves over a small range. When controlling high speeds with a greater centrifugal force, the lever ratio is made greater to meet speed variations.
* Lever ratio with adjusting lever at idle position
* Lever ratio with adjusting lever at full position
3) Starting the engine
With the engine stationary, the flyweights are in closed position and the idling and governor springs remain in the free-length state free from set tension.
Placing the adjusting lever in the full position moves the adjusting lever shaft, which causes the cancel spring B force to move the supporting lever. This in turn causes the control rack to move in the direction of greater fuel delivery. At the time, the sensor lever gets into the groove cut in the torque cam provided to increase the amount of fuel for startup, and the control rack, past the full load position, reaches the point to increase the amount of fuel for startup that is limited by the rack limiter.
By returning the adjusting lever to the idle position after the engine has started, the control rack is pulled to allow the sensor lever to leave off the groove in the torque cam. Thereafter, no fuel delivery increase can be obtained for startup even by moving the adjusting lever to the full position.
4) Idling control
Placing the adjusting lever in te idle position with the engine started makes Q the fulcrum of the floating lever.
As engine speed decreases, the centrifugal force of flyweights yields to the tension of idling spring, closing the flyweights. This causes the floating lever to pivot about Q, moving the control in the direction of greater fuel delivery, thus preventing the engine from stalling. (Condition indicated by solid line)
As engine speed increases, on the other hand, the idling spring tension yields to the flyweight centrifugal force, causing the control rack to move in the direction of smaller fuel delivery, thereby decreasing the speed. (Condition indicated by dotted line)
An idle speed is thus maintained at a point where the flyweight centrifugal force balances with the set tension of the start and idling springs.
The torque cam and sensor lever are not in contact with each other while the engine runs at idle.
5) Control of fuel injection rate at full load by torque cam
When the adjusting lever is placed in the full position under load, the floating lever pivots about P to move the control rack in the direction of greater fuel delivery. The sensor lever, at the same time, comes in contact with the torque cam. As speed varies, the shifter moves in the axial direction, which causes the tension lever to be pushed forward and backward around the tension lever shaft, making the torque cam to rotate around its shaft.
The sensor lever movement tracing along the cam surface displaces the control rack, thereby increasing or decreasing the fuel injection rate.
The tension lever movement from varying speeds does not, however, move the point R; it moves only P of guide lever and Q of supporting lever. The control rack is therefore moved through the sensor lever by the movement of torque cam.
6) Full speed control
With the adjusting lever at full position, the engine speed increases while the fuel injection rates under full load are controlled by the torque cam and sensor lever. This is accomplished when the centrifugal force of flyweights pushes the idling and governor springs to push forward the tension lever.
As speed further builds up and as the supporting lever contacts the L lever on the adjusting lever shaft by the cancel spring B, the floating lever pivots about Q to move the control rack in the direction of smaller fuel delivery, thus controlling the full speed.
The sensor lever, on the other hand, leaves the torque cam surface as this control advances.
7) Stopping the engine
Turning the starter switch to "ACC" with the adjusting lever at idle position causes the stop lever on top of governor to move in the stop direction through wire linkages from the starter switch. This causes the stop device plate to forcibly pull the control rack to the position with no fuel injection, thus stopping the engine.
Operating the stop lever with adjusting lever at any given position causes the stop device plate to pull the control rack in the direction of smaller fuel delivery. This in turn contracts the governor spring. As a result, the control rack is pulled until the set tensions of cancel spring B and governor spring balance; after this, the control rack does not move, only the supporting lever turning as the stop lever moves.
The cancel spring B absorbs excessive force being applied to internal levers when the accelerator pedal is depressed with the starter switch at "ACC".
(c) RU type governor <Option: 4DR5>
The RU governor is a mechanical governor employing the speed-up geares. It is a minimum-maximum governor that controls only the minimum and maximum speeds.
The governor gear is mounted, together with the camshaft bushing, at the rear end of the camshaft, secured with a round nut. Being in mesh with the pinion gear, it imparts rotary motion to the flyweights. The slip disc functions as a damper to prevent excessive wear in the gear due to engine speed variations.
The flyweights rotates at high speeds on the governor shaft secured to the governor housing, and the rotating and sliding surfaces are lubricated through the oil holes drilled into the governor shaft.
The flyweights when accelerated act to push the governor sleeve, in which there are two idle springs installed that control idle speeds. The spring tension is adjusted by shims. Full speed control is adjusted by the governor spring.
The floating lever is connected, at its bottom end, to the supporting lever which in turn is attached to the arm lever with a safety spring. An adjusting lever is installed on the adjusting lever shaft. At the center of the floating lever, there is a pin that fits into the groove in governor sleeve. At the top, the lever is attached to the shackle that is connected to the control rack. This configuration allows the adjusting lever motion and the governor sleeve motion by flyweight centrifugal force to be imparted to the control rack.
A stop lever is attached at the top part of the governor housing. There is also a damper spring installed at the top end of the floating lever that prevents the engine from hunting and stalling when it is suddenly decelerated.
1) Starting the engine
When the adjusting lever is placed in the full position for starting the engine, the floating lever pivots about the mid point to move the control rack in the direction of greater fuel delivery. Furthermore, since the flyweights are in the closed position, the start spring force causes the control rack to move to a point, past the full load position, to increase the amount of fuel for startup.
When the engine is started, the flyweight centrifugal force overcomes the start spring force, pulling the control rack back to the full load position.
2) Idling control
When the adjusting lever is placed in the idle position with engine started, the relatively small centrifugal force of flyweights yields to the governor spring tension, compressing only the idling spring to move the control rack, together with point A, in the direction of smaller fuel delivery. When the flyweight centrifugal force becomes smaller as the speed decreases, the idling spring moves the control rack, together with point A, in the direction of greater fuel delivery.
An idle speed is thus maintained at a point where the flyweight centrifugal force balances with the idling spring set tension.
When the idle speed remains constant, the damper spring is not in contact with the floating lever. When the engine is suddenly decelerated, the flyweights retain a great centrifugal force, which compresses the idling spring at a stroke causing the control rack to be pulled past the idle position to a point where no fuel injection is obtained. The damper spring then comes into contact with the floating lever preventing the control rack from moving to the no fuel delivery point.
3) Under cruising speed
While the engine is in operation, the idling spring remains in contact with the spring seat, and the point A becomes a fixed fulcrum. So, the control rack is moved in te direction of greater fuel delivery with the point A as a fixed fulcrum by the stroke the adjusting lever is moved from the idle to full position.
4) Full speed control
When the engine speed goes higher than the maximum with decreasing load, the flyweight centrifugal force becomes greater than the governor spring set tension, causing the governor sleeve to move to the right. Since the adjusting lever is unable to turn exceeding the full position, the floating lever starts to pull the control rack, with the point B as the fixed fulcrum, in the direction of smaller fuel delivey, while moving the point A to the right.
5) Supporting lever safety spring
While the vehicle goes down a hill, the engine is turned forcibly by the rear wheels.
At the time, the flyweight centrifugal force becomes greater even with the adjusting lever in idle position, which moves the governor sleeve to the right. However, since the control rack is blocked almost at its 0 position, an excessive centrifugal force of the flyweights is applied to the floating lever and shackle.
By installing a safety spring, its tension allows the adjusting and supporting levers to act simultaneously keeping the correct positional reference with each other, when there is no excessive force. When an excessive force is applied, only the supporting lever moves compressing the safety spring, by which the excessive force is absorbed.
6) Stopping the engine
Placing the adjusting lever in the idle position (where accelerator pedal is released) pulls the control rack in the direction of smaller fuel delivery.
When the starter switch is turned to "ACC" under above condition, the stop lever moves from the operation to stop position by wire linkages from the starter switch.
During this motion, one end of the stop lever comes in contact with the control rack shackle, compressing the idling and damper springs to move the control rack to the point where no fuel injection is obtained, thus stopping the engine.
When the accelerator pedal is depressed with the starter switch in "ACC" position, the governor adjusting lever moves from the idle to full position. This motion acts to move the point B at the bottom of floating lever to the right in illustration above.
The point A of the middle of floating lever, on the other hand, is pressed to the left by the strong governor spring tension, and which does not allow the point B to move to the right. Therefore, exceessive force are applied to the floating lever, shackle and other parts.
The safety spring as illustrated is provided to absorb such undue force.
When the accelerator pedal is depressed, only the adjusting lever moves compressing the safety spring.
When the engine is running, the stopper is, of course, free to move so that the adjusting lever and the stopper make the same motion under the tension of the safety spring.
When the adjusting lever is to be moved manually for cable replacement or other purposes, make sure that the adjusting lever is not moved beyond the contact with the stopper.
(d) MZ type governor <Option: 4DR5>
The MZ type pneumatic governor is an all-speed governor which, coupled with a venturi, controls fuel injection over the entire operating speed range of the pump.
The MZ type governor consists of an atmospheric chamber and negative pressure chamber split by a diaphragm. These chambers are connected with the venturi by hoses.
The diaphragm, coupled with the end of the control rack, is always kept pushed toward the maximum injection direction by the main spring. During operation of the engine, a difference between negative pressure and total pressure occurs at the venturi depending on the flow velocity of air, and moves the diaphragm to control fuel in keeping with the main spring.
The venturi used for this governor is a total pressure type which offers outstanding negative pressure characteristics. The venturi contains an auxiliary venturi for deriving the negative pressure to actuate the governor, a pipe connector and throttle valve. The intake air velocity which depends on the throttle valve opening and load produces a pressure difference between the auxiliary venturi and pipe connector. This pressure difference increases in proportion to the square of the air velocity. Therefore, even a small speed change produces a large pressure difference. Coupled with the performance of the MZ type governor, this capability assures outstanding engine speed control and prevents engine overrunning and hunting.
1) When starting engine
When starting the engine, the adjusting lever is set to the regular position to increase fuel supply for easier starting.
Namely, the stop lever moves to the left to compresses the full-load spring, moving the control rack beyond the position of maximum injectin amount of normal operation.
2) During idling
During idling, the throttle valve of the venturi remains almost fully closed, and a large negative pressure is produced in the negative pressure chamber.
As a result, the control rack stops at a position where the negative pressure and main spring pressure are in balance.
However, nearly a maximum negative pressure is reached during idling. Therefore, if only the function of the main spring is to be counted on, the fuel injection will drastically fall and will make it impossible to maintain the idling speed.
Further, use of only the main spring to control the engine speed will result in an unstable speed because the spring sensitivity is too high.
To solve these problems, the idling spring which offers a considerably larger pressure than the main spring is provided. During idling, cooperation of the idling spring with the main spring assures stable idling against the large negative pressure.
3) During maximum speed operation
When the throttle valve is in fully opened position, the control rack stays at the maximum injection position and is adjusted by the full-load spring capsule until the engine reaches the full-load spring capsule until the engine reaches the full-load maximum speed, because the negative pressure is small and the reaction force of the main spring is large.
When the full-load maximum speed is exceeded, however, the negative pressure increases, and compresses the main spring and idling spring, so the fuel injection is reduced and the engine reaches the no-load maximum speed.
Therefore, the maximum opening of the throttle valve should be adjusted so that the governor will start functioning at the full-load maximum speed.
4) Stopping engine
When the adjusting lever is pulled to the STOP position, the stop lever compresses the main spring and idling spring to move the control rack to the no-injection position, causing the engine to stop.
(3) Feed Pump
The feed pump is driven by the camshaft of the injection pump.
The priming pump makes it possible to manually lift fuel when the injection pump is stationary, so it can be used in bleeding the fuel system.
The gauze filter removes large particles of dust and dirt contained in the fuel lifted from the fuel tank to prevent clogging in the feed pump. Make sure the gauze filter is cleaned in gas oil at regular intervals.
The fuel is fed under pressure as described below. When the camshaft of the injection pump forces the push rod up, the fuel in the suction chamber is compressed and opens the outlet check valve. Most of the fuel forced out is drawn into the pressure chamber above the piston. When the cam, moved away by rotation of the camshaft, ceases to push up, the piston is pushed back by the pressure of the piston spring and forces out the fuel from the pressure chamber and forces it into the fuel filter.
At the time, the outlet check valve simultaneously closes, and the inlet check valve opens, so the fuel is drawn into the suction chamber.
If the pressure in the pressure chamber exceeds specification, the piston cannot be brought back by the pressure of the piston spring and stops the pump function. So the pressure in the fuel filter is adjusted not to rise more than necessary.
(4) Automatic Timer
The auto timer, of the mechanical type, varies automatically the injection timing according to the engine speed. Mounted on the injection pump camshaft with a round nut, it is driven by the idler gear in mesh with the injection pump gear.
The auto timer of 4D31 and 4D31-T models is forced-lubricated by the engine oil being injected into its center of rotation.
(a) SCZ type auto timer <Except for 4D31-T>
There is a hole at one end of the two flyweights. The pin of the timer hub fits in this hole.
The pin of the injection pump gear makes contact with the curved surface of flyweight. Timer springs are mounted to the pins of the timer hub and injection pump gear.
When the engine is running at low speeds, no centrifugal force is exerted to the flyweights, so the timer springs have the longest installed length.
At high engine speeds, on the other hand, the centrifugal force exerted to the flyweights causes them to open outward with the pin of the timer hub as the fulcrum. At the time the curved surface of flyweight tries to push the pin of the injection pump gear in the direction that the timer spring is compressed, but the pin, being on the drive side, cannot move. Accordingly, the pin of the timer hub is moved nearer toward the turning direction, while compressing the timer spring. As the result, the camshaft of the pump moves in the turning direction and advances the injection timing.
(b) SCDM type auto timer <4D31-T>
The SCDM type auto timer, of a mechanical type, varies the fuel injection timing automatically according to engine speed. Attached to the injection pump camshaft with round nuts, the auto timer is driven by the injection pump gear from the idler gear.
There are two pins opposing to each other press-fitted into the flange, to which the injection pump gear is attached. An eccentric smaller cam is installed on the pin, and mounted on the periphery of the smaller cam is a larger cam. The larger cams fit into the two holes in the timing flange, which causes the timing flange to turn as the flange rotates, thus driving the injection pump.
The two flyweights are installed with a given tension by the timer springs. The pins press-fitted into the flyweights are inserted into the holes in the larger cams.
With the engine running at low speed, the flyweights are unable to lift because of the timer spring set tension.
When the centrifugal force of flyweights becomes greater as the engine speed goes up, it overcomes the timer spring set tension allowing the flyweights to lift. This causes the larger and smaller cams to move in the turning direction.
Since the larger cams are fitted into the holes in timing flange, the motion of the cams is imparted to the timing flange, thus providing an advance.
(5) Injection Nozzle
The injection nozzles are of the hole type and the throttle type.
The fuel delivered from the injection pump enters the nozzle holder. When reaching the specified pressure value, the fuel overcomes the spring force to push up the needle valve of the nozzle tip, spraying from the injection orifice at the end of the nozzle into cylinder (hole type) or swirl chamber (throttle type).
The injection pressure can be adjusted by increasing or decreasing the number of washers in the spring.
(6) Fuel Filter
The fuel filter is of the spin-on type designed for ease of element replacement. The element is made integral with the outer casing, the center of the casing is being threaded.
(7) Water Separator <Option>
The sedimenter type water separator separates gas oil and water centrifugally by taking advantage of their difference in specific gravity.
The fuel that has flowed in from the inlet connector is squeezed by the fuel path of the head to increase the flow velocity and spins. The separated water is sedimented in the case, whereas the water-separated fuel is drawn through the fuel path in the center of the head into the feed pump.
The water separator sediments not only water but also mud components.
A red float goes up and down with the water level in the semitransparent case, making it possible to visually check the water quantity.
(8) Secondary Fuel Filter <Option>
Additionally mount this filter to the position shown in the right figure in case heavy A oil is used.
The fuel filter separates water from fuel delivered from the feed pump of the injection pump. It also removes dust through a filter paper element.
