The fuel supply system is designed to ensure a supply of fuel in the vehicle, clean it and supply it to the cylinders in strictly dosed portions in accordance with the operating procedure, speed and load conditions of the engine.
The power system also includes units for cleaning and supplying air to the cylinders, and a fuel supply control drive.
The diagram of the fuel supply system for the engine of the Ural-4320 and -4420 vehicles is shown in Fig. 1.
On Ural-43202 and -44202 vehicles, an additional fuel tank is not installed in the fuel supply system.
The main fuel tank is located behind the cabin; it is secured to the left frame side member using clamps and special brackets.
The capacity of the main fuel tank of the Ural-4320 and -43202 vehicles is 210 L, and the Ural-4420 and -44202 — 300 L.
An additional fuel tank with a capacity of 60 litres on Ural-4320 and -4420 vehicles is secured with clamps to the base of the spare wheel holder.
In case of a malfunction (fuel leak), remove the fuel tanks from the vehicle and repair them.
Before removal, drain the remaining fuel from the tanks, disconnect the fuel pipes, and on Ural-4320 and -4420 vehicles, additionally disconnect the sealing system pipes.
On the main fuel tank, disconnect the wire end from the fuel level sensor.
To remove the main and additional fuel tanks, unscrew the nuts of the clamp ends.
When loosening the nuts, keep the ends from turning with an adjustable spanner.
It is more convenient to remove the main fuel tank if the bracket angle is removed.
Before repairs, rinse the fuel tank inside and out with a 5% caustic soda solution, followed by rinsing with hot water until all traces of fuel are completely removed.
Cracks and holes in the walls of fuel tanks should be repaired by soldering or welding.
Large holes should be repaired by applying patches made of sheet steel.
The patch should overlap the edges of the hole by 20-25 mm. Thoroughly clean the soldering or welding areas with a file, scraper, wire brush or sandpaper to remove paint, rust and dirt.
Before and after repair, check the fuel tank with an air pressure of 0.3 kgf/cm2 by immersing the area being tested in water.
The coarse fuel filter (Fig. 2) is located in the engine compartment and is secured with two bolts to the right side of the bonnet.
During operation, periodically drain the fuel sediment from the filter through drain plug 1, disassemble and wash the filter parts.
To disassemble the filter, unscrew four bolts 7, remove the bowl 2, unscrew the deflector 5 together with filter 4. Wash filter 4 and other parts, and install them in place.
The fine fuel filter (Fig. 3) is mounted on a special bracket to the front of the engine.
A valve is mounted in the filter housing for discharging excess fuel and air trapped in the system into the main fuel tank.
To ensure effective collection of air trapped in the system, the filter is located above the other units of the engine fuel supply system.
During the operation of the vehicle, periodically replace the filter elements 7 in the filter and wash the internal cavity of the caps.
To replace the filter elements, unscrew the bolts 2, remove the caps 8, drain the fuel from the caps and remove the filter elements 7.
Rinse the inner cavity of the caps with unleaded petrol or clean diesel fuel, install new filter elements, gaskets 6 and assemble the filter.
Check the filter for leaks with the engine running. In case of fuel leakage, tighten bolts 2.
If the fuel leak is not eliminated by tightening the bolts, check the condition of the sealing gaskets 5 and washers 3. If damaged, replace them.
In case of interruptions in the fuel supply to the high-pressure fuel pump, check the operation of the jet valve 6 (Fig. 4).
The jet valve transfers fuel and accumulated air from cavity "A" in the filter housing into cavity "B", connected by fuel pipes to the main fuel tank.
The beginning of fuel flow from cavity "A" to cavity "B" occurs at a pressure in cavity "A" of 1.3-1.7 kgf/cm2.
If the fuel pressure at the beginning of the flow does not correspond to the above, adjust it by changing the thickness of the washer pack 2.
Increasing the thickness of the washer pack will increase the pressure at which fuel begins to flow.
Injectors (Fig. 5) are installed hermetically in special sockets of the cylinder heads and are attached to them with brackets and nuts.
During the operation of the vehicle, periodically remove the injectors for inspection and adjustment under bench conditions.
To remove the injectors from the engine, unscrew the nuts and remove the brackets securing the fuel pipes.
Unscrew the union nuts securing the fuel pipes to the injectors and the high-pressure fuel pump, and remove them.
Unscrew the fuel line bolts and disconnect the drain pipes from the injectors.
Unscrew the nuts, remove the brackets and remove the injectors from the cylinder head sockets using puller I-801.11.000.
After disconnecting the fuel lines, the fittings on the high-pressure fuel pump and the removed injectors, as well as the openings of the removed fuel pipes, must be protected from foreign objects and dirt (with plugs, caps, blanking plugs, insulating tape).
Disassembly, assembly and adjustment of injectors should be carried out in a special room using devices and test stands under high cleanliness conditions.
When disassembling and assembling injectors, do not touch the working surface of the needle 14 with unprotected hands (see Fig. 5).
Disassemble and assemble the injectors using the I-801.20.000 device (Fig. 6), and check and adjust them using instruments of the KP-1609 type or on the KI-3333 test stand.
When checking and adjusting, determine the pressure at which the injector needle begins to lift, the quality of fuel atomisation and the tightness of the nozzle locking cone.
The pressure at which the needle begins to lift should be 180-185 kgf/cm2 and should be adjusted by the thickness of the pack of adjusting washers 11 (see Fig. 5).
A change in the thickness of the washer pack by 0.05 mm leads to a change in the pressure at which the needle begins to lift by 3.0-3.5 kgf/cm2.
As the thickness of the pack of adjusting washers increases, the pressure at which the injector needle begins to lift increases; as it decreases, it decreases.
The quality of fuel atomisation by an injector is considered satisfactory if, when fuel is supplied to the injector with a frequency of 70-80 lever strokes per minute, it is injected into the atmosphere in a mist-like state and is evenly distributed over the cross-section of the spray cone.
Fuel should be injected from all four holes of the injector nozzle. The beginning and end of the injection must be clear.
Fuel injection from a new injector is accompanied by a characteristic sharp sound.
The absence of a sharp sound in used injectors is not a disadvantage.
If one or more nozzle holes in the nozzle body are coked, if there is leakage along the needle cone, or if it is necessary to adjust the pressure at which the nozzle needle begins to lift, disassemble the injector and wash the injector parts in unleaded petrol or filtered diesel fuel.
Clean the nozzle holes with steel wire with a diameter of 0.25 mm, and clean the outside of the nozzle with a wooden block soaked in engine oil or a brush made of brass wire.
To disassemble the injector, it is necessary (see Fig. 5) to unscrew nut 2, remove the nozzle body 1 together with needle 14, spacer 3, pushrod 5, spring 13 and adjusting washers 11.
Unscrew fitting 8, remove sleeve 10 and filter 9. When disassembling, protect needle 14 from accidentally falling out of nozzle body 1.
When disassembling, washing and assembling, protect the injector parts from being mixed up.
To do this, wash and store the parts of only one injector in a separate bath with filtered diesel fuel before assembly.
After washing, to protect against damage and mixing up, needle 14 must be in the nozzle body.
Assemble the injector in the reverse order of disassembly. Before assembly, lubricate the injector parts with diesel fuel.
Tighten nut 2 (tightening torque 7-8 kgf·m). After assembly, adjust the injector to the pressure at which the nozzle needle begins to lift and check the quality of fuel atomisation.
The nozzle body and needle form a precision pair, in which replacement of any one part is not allowed; therefore, if necessary, they must be replaced only as a pair.
The newly installed pair (needle and nozzle) must have a marking on the nozzle body.
Installation of other types of nozzles is not allowed, as this can lead to an increase in smoke and exhaust gas temperature, metal burnout on the piston crowns and cylinder heads, and a decrease in power and economic performance.
