The engine power system includes components, parts and assemblies designed for thorough cleaning and uniform distribution of strictly metered portions of fuel over the cylinders

The power system works as follows.

Fuel from the fuel tank 4 is sucked in by the fuel priming pump 5 through the coarse fuel filter 3.

From the pump, the fuel enters the fine filter 1, in which it is finally cleaned of the smallest contaminants and then enters the high pressure pump 6.

From the pump, metered portions of fuel are supplied through high-pressure fuel lines to injectors for injection into the cylinders.

The fuel priming pump delivers more fuel to the high pressure pump than is necessary for engine operation.

Excess fuel is drained through the fuel pump bypass valve back to the fuel tank.

Power System Diagram

The bypass valve, adjusted to a fuel pressure of 0.5-1.0 kgf / cm2, creates a constant fuel pressure in the pump channels, which ensures good filling conditions above the plunger space with fuel, regardless of the speed engine crankshaft.

In addition, circulation through the bypass valve helps to remove air bubbles from the fuel, which, if they enter the pump plunger space, can adversely affect the fuel supply.

The removal of air bubbles from the fuel is also facilitated by the continuous circulation of fuel through the jet of the race filter and through the fuel line to the tank.

Fuel leaking into the nozzle spring cavity through the gap between the needle and the atomizer is discharged into the fuel tank.

Possible malfunctions of the power supply system and how to fix them

The main malfunctions of the power system include:

  • - leakage of fuel lines and their connections;
  • - insufficient fuel supply to the injection pump;
  • - violation of the normal operation of the injection pump and injectors.

Breaking the tightness of fuel lines and their connections

A common cause of difficulty starting the engine, its unstable operation, power loss is the ingress of air into the fuel system.

Leaks in the suction part of the fuel system have a particularly strong effect on the operation of the engine: fuel tank - fuel priming pump.

The slightest leak in the connections in this area entails the ingress of air into the power system, which reduces the supply of fuel to the combustion chamber and leads to a malfunction of the engine.

If it is difficult to start the engine, then to remove air from the power system, you need to unscrew the handle of the manual booster pump and, moving it up and down, pump the system for 2-3 minutes.

After pumping, turn the pump handle all the way.

If even after pumping the system, starting the engine continues to be difficult and the engine does not develop power, then wipe the fuel lines, joints, booster pump, coarse filter cover, fine filter with a rag and determine the place of air leakage.

The tightness of the low-pressure fuel lines from the fuel priming pump to the high-pressure pump can be checked with a hand pump, for this, the drain fuel line is disconnected from the tank and plugged with a plug, then several strokes are made with a hand pump.

Where the system is leaking, emulsion or fuel will leak out.

Leaks in the connections are eliminated by tightening the threaded connections, replacing the corresponding seals or fuel lines.

If the place of air leakage cannot be found, it is recommended to remove the coarse fuel filter housing from the fuel tank and check it for leaks.

After the suction is eliminated, it is necessary to remove air from the power system, to do this, loosen the air release plugs from the high-pressure fuel pump housing and pump the system with a hand pump until fuel flows out without air bubbles. Then the corks are wrapped.

Insufficient fuel supply to the injection pump.

Violation of the normal circulation of fuel in the system is expressed in a drop in engine power, uneven and unstable operation, difficult starting, engine stops during operation at a low crankshaft speed.

Insufficient fuel supply to the injection pump can be caused by:

  • - suction of air into the power system;
  • - malfunction of the fuel priming pump;
  • - fuel leakage at the junctions of high-pressure fuel lines;
  • - clogging of the filter element of coarse or fine fuel filters, as well as fuel lines;
  • - water freezing in winter in fuel lines or fine filter;
  • - thickening fuel consumption if the type of fuel is not appropriate for the season and the car is stored in an open area.

Before looking for a malfunction, you should make sure that there is fuel in the fuel tanks and that there is no leakage of fuel at the junctions of the high pressure fuel lines.

Then you need to check the system for air leaks and, if necessary, fix the problem.

If the fuel supply is not interrupted when pumping with a hand pump, then the booster pump is most likely faulty.

The most common causes of abnormal operation of the booster pump are: dirt between the seats and valves, broken springs or stuck pistons.

If, after flushing and purging the valve parts, the normal operation of the pump is not restored, then the booster pump must be removed from the engine and sent to a workshop for repair.

The intensity of fuel circulation in the system can be checked using a control pressure gauge connected to the hole for the plug on the injection pump housing to release air, the air pressure in the line should be within 0.5 - 1 kgf / cm2, at a crankshaft speed of 2100 min.

Pressure below 0.5 kgf/cm2 may be caused by clogging of the filter elements of the coarse or fine fuel filters or clogged fuel lines.

In this case, the filter elements are replaced with new ones, and the fuel lines are blown with compressed air.

If even after replacing the filter elements of the fine and coarse filters and checking the fuel priming pump, the pressure in the system remains below normal, then check the condition of the bypass valve of the high pressure fuel pump.

A malfunctioning bypass valve can be caused by dirt getting in between the valve seat and the valve, or by a broken or weakened valve spring.

The pressure can be adjusted by turning the seat of the high-pressure pump bypass valve, and after adjusting, the valve seat can be caulked.

If the bypass valve is in good condition, then the injection pump must be removed from the engine and sent to a workshop for inspection and repair.

Violation of the normal operation of the injection pump and injectors

If the engine does not develop power, smokes, runs unevenly at low speeds, then this most often indicates poor operation of the injectors (in the absence of air leakage).

The main cause of incorrect operation of the injectors is the deterioration of the quality of the fuel spray.

This phenomenon occurs due to a violation of the pressure adjustment of the beginning of the needle lift, the ingress of various mechanical impurities into the atomizer, coking, clogging or wear of the holes in the atomizer body, as well as improper assembly or installation of nozzles on the engine.

A faulty injector can be detected directly on a running engine, to do this, loosen the union nut at the fitting of the injector to be checked so that no fuel enters it.

Turning off the nozzle from work, monitor the quality of the exhaust gases and the engine speed.

If, after turning off the nozzle from operation, the engine speed does not change, and the exhaust smoke decreases, then the nozzle being checked is faulty - it must be removed and sent for repair.

When a working injector is turned off, the engine speed will decrease, and the smoke of the exhaust gases will not change.

If necessary, it is recommended to start checking the high-pressure fuel pump only after checking the injectors, making sure that they are in good condition.

During operation, the normal operation of the pump may be disrupted due to mechanical wear of the plunger pairs and discharge valves, breakage of the pusher springs, wear of the bypass valve or its seat, due to the thread breaking of the fittings at the junction of the high-pressure fuel lines and violation of the pump adjustments.

As a result of the wear of the plunger pairs, the fuel supply by the pump sections per cycle is reduced, which leads to a decrease in engine power and efficiency.

The wear of the discharge valves along the shut-off cone and the relief belt changes the beginning and nature of the injection, and also worsens the cut-off of the fuel supply by the nozzle needle.

This leads to fuel leakage through the atomizer and coking of the nozzle spray holes.

Wear of the bypass valve causes a decrease in fuel pressure in the pump cavity and leads to a deterioration in the filling of the space above the plunger.

In the conditions of repair and mechanical workshops, the repair of fuel equipment in most cases comes down to replacing unusable parts, monitoring and adjusting fuel equipment.

Repair should be carried out in departments or workshops of fuel equipment equipped with the necessary devices, tools, control and adjustment stands and devices.

It is recommended to disassemble the injection pump, the fuel priming pump and the injection advance clutch only after examining the technical no condition and in the amount necessary to eliminate the identified shortcomings, since unjustified disassembly violates the mutual running-in of parts to each other, leads to a decrease in the service life of the assembly as a whole.

In all cases, when removing the fuel equipment from the engine after disconnecting the fuel lines, the fittings of the fuel and booster pumps, injectors, filters and pipeline openings must be protected from dirt by plugs, caps, plugs or clean insulating tape.

Before disassembly, the units and components of the fuel equipment are thoroughly cleaned and washed in pure kerosene.

In this case, it is necessary to exclude the possibility of contaminated fuel getting into the internal cavities of the fuel equipment.

During the assembly and disassembly, the parts and components of the fuel equipment must be thoroughly washed and placed in a clean container to ensure their safety from damage and corrosion.

When assembling all units of the fuel equipment, it must be remembered that the plunger and valve pairs, injector nozzles, as well as the bushing with the booster pump rod are precision pairs and cannot be decommissioned. They can only be replaced as a set.