The fuel supply system ensures the filtration of the fuel and its uniform distribution among the engine cylinders in metered portions at strictly determined moments.
The engine uses a split-type fuel supply system, consisting of the fuel tank, low-pressure fuel lines, coarse and fine fuel filters, the priming and fuel feed pumps, the high-pressure fuel pump (HPFP), high-pressure fuel lines, injectors, a solenoid valve and the pin glow plugs of the electric flame preheater (EFPH).
The fuel tank, the coarse fuel filter and the priming pump must be installed on the product on which the engine is used; all the other elements of the fuel system are installed directly on the engine.
The diagram of the engine fuel supply system is shown in Figure 1.
The fuel from the fuel tank 26, through the coarse filter 29 and the priming pump 30, is delivered by the fuel feed pump 18 along the fuel tube 13 into the fine filter 16.
From the fine filter, along the low-pressure fuel tube 14, the fuel enters the HPFP 21, which, in accordance with the cylinder firing order, distributes the fuel along the high-pressure fuel lines 1–8 to the injectors 10.
The injectors inject the fuel into the combustion chambers.
The excess fuel, together with the air that has entered the system, is diverted to the fuel tank through the bypass valve 24 and the valve 23.
The injector of model 273-20 or 273-50, of closed construction, with five spray orifices and hydraulic control of the nozzle needle lift, is shown in Figure 2.
All the parts of the injector are assembled in the body 6. To the lower end face of the injector body, by the nut 2 through the spacer 3, the nozzle body 1 is pressed, inside which the needle 12 is located. The nozzle body and the needle form a precision pair.
The angular fixing of the nozzle body relative to the spacer and of the spacer relative to the injector body is ensured by the pins 4.
On the upper end of the nozzle needle, through the rod 5, the spring 11 exerts pressure.
The necessary tension of this spring is achieved by a set of adjusting shims 9, 10, installed between the spring and the end face of the inner cavity of the injector body.
The fuel is supplied to the injector under high pressure through the union 8 with the slot filter 13 built into it, then along the channels of the body 6, the spacer 3 and the nozzle body 1 — into the cavity between the nozzle body and the needle 12 and, lifting it, is injected into the engine cylinder.
The fuel that has seeped through the clearance between the needle and the nozzle body is diverted along the channels in the injector body and drained into the tank through the drain tubes 9 and 11 shown in Figure 1.
The injector is installed in the cylinder head, fixed by clamps secured by a nut. The end face of the nozzle nut is sealed against gas breakthrough by a corrugated copper gasket.
The sealing ring 7 (Figure 2) prevents dust and liquids from entering the cavity between the injector and the cylinder head.
The installation of injectors of other models is categorically prohibited!
The high-pressure fuel pump (Figure 3) is intended to deliver to the engine cylinders, at determined moments, strictly metered portions of fuel under high pressure.
On the automotive version of the engine, an HPFP with an all-speed governor is installed.
HPFP characteristics
- Type: 337
- Section firing order: 8-4-5-7-3-6-2-1
- Camshaft rotation direction (from the drive side): right-hand
- Plunger diameter, mm: 11
- Plunger stroke, mm: 13
- Rated camshaft speed: 1100 min-1
Camshaft speed of the pump when the governor control lever rests against the maximum speed limiting bolt, min-1:
- with complete cut-off by the governor of the fuel supply through the injectors, not more than: 1280
- at the beginning of the cut-off by the governor of the fuel supply through the injectors: 1140–1160
Pre-stroke of the plunger (from the beginning of its movement to the geometric beginning of delivery in the eighth section), mm: 5.65 ± 0.05
Alternation of the beginning of fuel delivery according to the camshaft rotation angle, degrees: 0–45–90–135–180–225–270–315
Maximum force on the governor control lever at the rated operating mode of the pump on a 50 mm arm, N (kgf): 127.5 (13)
Rated cyclic delivery, mm³/cycle:
- for HPFP model 337-20.03: 132–137
- for HPFP model 337-20.04: 147–152
In the HPFP housing 1 (Figure 3), eight sections are installed, each consisting of the housing 6, the plunger sleeve 8, the plunger 7, the rotating sleeve 4, the delivery valve 11, whose seat is pressed against the plunger sleeve 8 by the union 12.
The plunger performs a reciprocating movement under the action of the cam of the shaft 46 and the tappet spring 3.
The tappet is secured against turning in the housing by the key 14.
The camshaft rotates in roller bearings 45, installed in steel rings pressed into the pump housing and pressed by covers.
The bearing interference of the camshaft must be 0.05–0.15 mm and is adjusted by the shims 44.
To change the fuel delivery, the plunger 7 is turned with the aid of the sleeve 4, connected through the follower axle to the rack 5 of the pump. The rack moves in the guide sleeves 40.
The holes for the guide sleeves in the HPFP housing, on the drive side, are closed by the plugs 39.
On the opposite side of the pump is the charge air pressure fuel delivery corrector 24.
On the front end face of the housing, at the point where the fuel leaves the pump, the bypass valve 38 is installed, which ensures a pressure in front of the inlet orifices of the plungers in the operating modes of 0.13–0.19 MPa (1.3–1.9 kgf/cm²).
The lubrication of the pump is by circulation, under pressure from the common lubrication system.
The HPFP speed governor (Figure 4) is of the all-speed, direct-acting type; it changes the quantity of fuel supplied to the cylinders depending on the load, maintaining the prescribed crankshaft speed.
The governor is installed in the centre of the HPFP housing. On the camshaft of the pump, the governor drive gear 16 (Figure 3) is installed, the rotation of which is transmitted through the rubber keys 17.
The driven gear is made integral with the weight holder 28, rotating on two ball bearings.
When the holder rotates, the weights 31, swinging on the axles 29, diverge under the action of centrifugal forces and, through the thrust bearing 30, displace the governor sleeve 32, which, resting against the pin 34, in turn displaces the governor levers 2, 8 and 9 (Figure 4), overcoming the force of the spring 5.
The lever 2 is connected by a pin to the right rack 3 of the fuel pump. The right rack is connected through the rack lever 7 to the left rack 11.
The diagram of the speed governor operation is shown in Figure 5.
The governor control lever 16 is rigidly connected to the lever 12. To the lever 12 the governor spring 13 is attached, and to the levers 14 and 11 — the starting spring 15.
During the operation of the governor, the centrifugal forces of the weights are balanced by the force of the spring 13.
When the crankshaft speed increases, the weights, overcoming the resistance of the spring 13, displace the levers 2, 4 and 9, and with them the HPFP racks — the fuel delivery decreases.
When the crankshaft speed decreases, the centrifugal force of the weights decreases, and the levers with the HPFP rack, under the action of the spring force, move in the opposite direction — the fuel delivery and the crankshaft speed increase.
When the governor lever 9 rests against the bolt 6 and the crankshaft speed is less than 1800 min-1, the direct corrector spring 10 displaces the pump racks (through the levers 2 and 4) in the direction of increasing the fuel delivery, ensuring the required value of the maximum engine torque.
The inverse corrector spring 3, at a speed of less than 1400 min-1, displaces the lever 4 with the racks in the direction of decreasing the fuel delivery, limiting the maximum exhaust smoke opacity of the engine.
The fuel delivery is stopped by turning the engine stop lever 3 (Figure 6) until it rests against the bolt 5.
At this, the lever 3, having overcome the force of the lever spring 33 (Figure 3) and the spring 5 (Figure 4), through the pin 14 will turn the levers 2, 8 and 9, the racks will move until the fuel delivery is completely stopped.
The checking and adjustment of the HPFP, as well as the replacement of the plunger pairs and the sealing rings of the HPFP sections, must be carried out in a specialised workshop by a qualified specialist.
The installation on the engines 740.50-360 and 740.51-320 of HPFPs of other models than those indicated above is prohibited, in order to avoid failure of the engine!
The charge air pressure fuel delivery corrector (Figure 7) reduces the fuel delivery when the charge air pressure drops below 40–45 kPa (0.4–0.45 kgf/cm²), thereby providing thermal protection of the engine and limiting the exhaust smoke opacity.
In the corrector housing 1, the piston 26 with the spool 2 is installed. The spring 27 acts on the piston, fixed by the plate 25 and the ring 3.
Into the piston, the stud 29 with the end piece 31, which is the nominal stop in the governor, is screwed and locked by the nut 28.
The end piece is locked by the nut 30. The spring 7 acts on the spool 2, its pre-tension can be changed by the adjusting screw 11.
To the corrector housing 1, through the gasket 4, the diaphragm housing 8 is attached.
Into it, the diaphragm assembly with the rod is installed (parts 24, 16, 17, 23, 22, 19, 18). The diaphragm is clamped between the housing 8 and the cover 21.
In the diaphragm housing 8, on the axle of the lever 13, the corrector lever 12 is installed, the rotation of which is limited by the adjusting screw 15.
The fuel delivery corrector is not of the direct-acting type: when the charge air pressure in the diaphragm cavity changes, the position of the spool changes, which, in turn, determines the position of the corrector piston.
Into the cavity «А» between the corrector housing 1 and the piston 26, through a threaded hole and a 0.7 mm jet in the corrector housing (not shown in the figure), oil under pressure from the engine lubrication system is supplied.
The piston, under the action of this pressure, compressing the spring 27, moves to the left until the windows in the piston and the spool open and the oil goes to drain.
At this, a constant oil flow rate through the corrector is established.
When the position of the spool changes, the piston moves after it (follow-up system).
Through the threaded hole of the cover 21, air from the engine intake manifold is supplied into the diaphragm cavity.
When the air pressure drops below 0.05 MPa (0.5 kgf/cm²), the force of the corrector spring 7, acting on the spool, becomes greater than the force created by the charge air pressure on the diaphragm and transmitted through the diaphragm rod and the corrector lever also to the spool.
The spool moves to the right until the equilibrium of the forces acting on it is reached.
Following the spool, the piston with the stud 29 and the end piece 31 also moves to the right, displacing to the right the governor lever 8 (Figure 4) resting against it.
Following the governor lever, under the action of the centrifugal forces of the weights, the levers 9, 2 and 7 with the pump racks move in the direction of decreasing the fuel delivery.
Adjustment of the corrector
The corrector has two external adjustments — the screws 11 and 15 (Figure 7).
By the screw 11, the pre-tension of the corrector spring 7 is changed, thereby changing the beginning of the corrector actuation.
If it is necessary to increase the value of the charge air pressure at which the corrector begins to actuate, the screw 11 is screwed in, increasing the pre-tension of the spring 7.
By the screw 15, the rated cyclic fuel delivery is adjusted. When the screw 15 is unscrewed, the fuel delivery increases.
If it becomes necessary to remove the corrector, it is first necessary to measure the protrusion of the stud end piece 31 relative to the rear end face of the HPFP housing, and after installing the corrector in place, restore the value of this protrusion and lock the end piece with the nut 30.
The HPFP drive is shown in Figure 8. It consists of the HPFP drive shaft 6 with the packs of front 7 and rear 8 compensating plates, the driven half-coupling 2, the driven half-coupling flange 3, the centring flange 4, the driving half-coupling 9 and the centring sleeves 5.
Each pack of compensating plates consists of 5 plates 0.5 mm thick each.
All the bolts in the HPFP drive, except for the bolt pos. 10, must be of strength class R100 and be tightened to a torque of 65–75 N·m (6.5–7.5 kgf·m).
The tightening of all the bolts must be checked with a torque wrench. Before installing the bolts, check for the presence of the centring sleeves.
Deformation (bending) of the front and rear compensating plates is not permitted. The bolt 10 of the driving half-coupling must be tightened last, to a torque of 78.4–84.3 N·m (8–8.6 kgf·m).
The fine fuel filter is shown in Figure 9. It is intended for the final purification of the fuel from fine particles before entering the HPFP.
The filter is installed at the highest point of the fuel supply system to collect and divert to the tank the air together with part of the fuel through the valve (Figure 10), installed on the bypass from the filter.
When replacing the filter elements, the rules for servicing the fuel supply system must be strictly observed.
Do not allow contaminants to enter the system and use only filter elements of the following models: 740.1117040-01, 740.1117040-02, 740.1117040-04.90.
The valve is presented in Figure 10.
When the pressure in the cavity «А» of the fuel supply reaches 25–45 kPa (0.25–0.45 kgf/cm²), the ball 4 moves and the fuel flows from the cavity «А» into the cavity «Б» through the jet 5 of the valve.
The fuel feed pump 13 (Figure 3) of the piston type is intended to supply fuel from the tank, through the coarse and fine filters and the priming pump, to the inlet cavity of the HPFP.
The pump is installed on the rear cover of the governor; its drive is provided by the eccentric 19, located at the rear end of the HPFP camshaft.
In the pump housing, the piston, the piston spring, the rod sleeve 47 and the tappet rod 48, the inlet and delivery valves with springs are located.
The eccentric 19, through the roller 49, the tappet 15 and the rod 48, imparts a reciprocating movement to the piston of the fuel feed pump.
The diagram of the pump operation is shown in Figure 11. When the tappet 9 is lowered, the piston 1, under the action of the spring 4, moves downwards.
In the cavity «А», a vacuum is created and the inlet valve 2, compressing the spring 3, admits the fuel into the cavity «А».
At the same time, the fuel located in the delivery cavity «В» is displaced into the line «Г», while the valve 5, under the action of the spring 6, closes, preventing the flow of fuel from the cavity «В» into the cavity «А».
When the piston 1 moves upwards, the fuel filling the cavity «А», through the delivery valve 5, passes into the cavity «В» under the piston, while the inlet valve closes.
When the pressure in the delivery line increases, the piston does not perform a full stroke following the tappet, but remains in the position determined by the equilibrium of the fuel pressure force on the one hand and the spring force on the other.
The priming pump 10 (Figure 11) of the piston type serves to fill the fuel system with fuel before starting the engine and to remove air from it.
The pump consists of the housing, the piston, the cylinder, the inlet and delivery valves.
The fuel system should be primed with the aid of the pump piston, after first unlocking it by turning it anticlockwise.
When the piston 11 moves upwards, a vacuum is created in the space under it. The inlet valve 12, compressing the spring 14, opens and the fuel enters the cavity «Д» of the pump.
When the piston moves downwards, the inlet valve closes and the delivery valve 13 opens; the fuel under pressure enters the delivery line, ensuring the removal of air from the engine fuel system through the fine fuel filter valve and the HPFP bypass valve.
After priming the system, it is necessary to lower the piston and lock it by turning it clockwise.
At this, the piston is pressed against the end face of the cylinder through a rubber gasket, sealing the suction cavity of the priming pump.
It is not permitted to start the engine with the piston unlocked, due to the possibility of air being drawn in through the piston seal.
The fuel lines are divided into low-pressure fuel lines — 0.4–2 MPa (4–20 kgf/cm²) — and high-pressure fuel lines — more than 20 MPa (200 kgf/cm²).
The low-pressure fuel lines are made of a steel tube of 10 mm cross-section with soldered end pieces.
The high-pressure fuel lines are of equal length (l = 595 mm), made of steel tubes of internal diameter 2+0.05 mm by upsetting at the ends connecting cones with crimping washers and union nuts for connection to the unions of the HPFP and the injectors.
In order to avoid breakages from vibration, the fuel lines are secured by clamps to the intake manifolds.
