Citroen Xantia

since 1993 of release

Repair and car operation

Power supply system - diesel models

General information

Thermostat assembly / fuel filter

Into number of components of a power supply system enter: established in a back part of the car a fuel tank, the fuel filter with the built-in moisture separator, the fuel pump of a high pressure (TNVD), a nozzle of injection of fuel and accompanying elements. Before passing through the filter, fuel is warmed up at the expense of run of cooling liquid of the engine through the basis of a casing of thermostat/assembly of the filter (see an illustration thermostat Assembly / the fuel filter). Intensity of heating is defined by ambient temperature. If the temperature of air makes less 15°С, the thermostatic element rises from the situation "and", fuel arrives via the union "s", passes through “d” opening, is warmed up, passing through e and b channels and is brought to the filter. At air temperature from 15°С to 35°С the valve of the thermostat opens only partially, thus only the part of fuel passes directly from "with" to “b”. The additional complete set of some models includes the turbo-supercharging system which compressor is equipped with the built-in cooler (Intercoоler).

Supply of fuel from a fuel tank in TNVD is carried out by means of the lopastny submitting pump built in TNVD. Before absorption in the pump fuel passes through the filter where there is its cleaning of extraneous inclusions and moisture particles. Excess of fuel goes on greasing of moving components of the pump, and then comes back back to a tank.

Arrangement of the TNVD external components of Lucas system

Arrangement of the TNVD external components of Bosch system

TNVD rotates with the frequency equal to a half of frequency of rotation of a cranked shaft, and is put in action from a gas-distributing belt. Szhimaniye of fuel to a high pressure at which its successful mixing with the compressed air in vortical chambers is guaranteed, in TNVD of Bosch system is made by means of the kulachkovy plate putting in action the unique piston. In pumps of production of Lucas (CAV) firm two antidirected pistons compress the volume which was between them at the expense of the rollers rotating in a kulachkovy ring. Further fuel passes through the central rotor with the unique target drilling combined with ports, conducting to tubes of nozzles (see illustrations the Arrangement of the TNVD external components of Lucas system and the Arrangement of the TNVD external components of Bosch system).

Management of a dosage of submitted fuel is made by the centrifugal regulator reacting to the provision of a pedal of gas and turns of the engine. The regulator is connected to the dosing-out valve which makes correction of amount of injected fuel on each step of the piston of the pump. On models with a turbo-supercharging the additional device makes increase in supply of fuel at increase of pressure of pressurization.

Base installation of phases of a gazoraspredeleniye is made at pump installation. In engine operating time the mechanism of rotation kulachkovy plates/rings automatically corrects parameters for the purpose of achievement of maximum efficiency of return of the unit.

Four nozzles carry out injection of homogeneous streams of fuel in located in a head of cylinders vortical chambers. Nozzles are calibrated so that to open and be closed at certain critical pressure that guarantees maximum efficiency and uniformity of combustion of a mix. Operating needles of nozzles are greased with the arriving fuel collecting in spring chambers and then arriving in a returnable hose of TNVD on by-pass tubes.

Depending on engine type on cars systems of injection of production of Bosch or Lucas firms can be established. Components of system can be marked by inscriptions of "CAV", “Roto-Diesel” or “Con-Diesel”, depending on a date of issue and a territorial arrangement of manufacturer. Except for the fuel filter, all replaceable components should have the same marking, as removed from the car.

Efficiency of cold start raises at the expense of preliminary heating, or by means of the candles of an incandescence established in vortical chambers. The thermosensitive sensor of system of cooling operates the lever of turns of fast idling on TNVD, providing increase of frequency of rotation of the engine idling at start of the cold engine. On models with a turbo-supercharging correction of an advancing of the moment of injection is carried out by means of the special, filled capsule cooling with liquid.

The system of a turbo-supercharging allows to increase efficiency of return of the engine at the expense of pressure forcing in the inlet pipeline above the atmospheric. Now air instead of simply being soaked up in cylinders, will force the way in them under a pressure. The increase in supply of fuel is carried out by TNVD in proportion to increase in amount of arriving air.

Functioning of a turbokompressor is carried out at the expense of energy of the fulfilled gases. Gases pass through special a form a casing (a turbine casing), putting in action a turbine wheel. The wheel is fixed on a shaft on which other end the second scapular wheel called by a wheel of the compressor is located. The wheel of the compressor rotates in own casing and carries out compression of the soaked-up air submitted then to the inlet pipeline.
On the way from a turbokompressor to the inlet pipeline air passes through the special built-in cooler (Intercoоler) representing the heat exchanger, "air-air" functioning on the scheme and established near a radiator of system of cooling of the engine. Cold air is delivered to the heat exchanger of the built-in cooler created at the expense of car movement by a counter running flow. A problem of a cooler is selection of surpluses of heat which is forming at a szhimaniye of air in a turbokompressor. Thus efficiency of return of the engine in addition increases in view of increase of density of the cooled air.

Restriction of size of pressure of pressurization (pressure in the inlet pipeline) is limited at the expense of functioning of the special waste zaslonka making removal of fulfilled gases from a wheel of the turbine at operation of the actuation mechanism sensitive to pressure. The sensor switch sensitive to pressure makes inclusion of a control lamp on the car dashboard in case of excess by pressure of pressurization of the maximum admissible level.

Greasing of a shaft of the turbine is carried out submitted under a pressure on a special tube impellent oil. The system of greasing is arranged in such a manner that the shaft appears is hung out on an oil pillow. Further oil on a returnable tube goes back to the pallet of a case of the engine. On some models additional security measures against a turbine overheat, at the expense of its connection with a path of system of cooling of the engine are accepted.

Under condition of regular performance of procedures of routine maintenance of the car, the equipment of a power supply system should serve rather long time smoothly. Service life actually TNVD in normal conditions exceeds engine service life. The main reason of an exit of the pump and injection nozzles out of operation usually is hit in dirt and moisture fuel.

The range of procedures of service of TNVD and the nozzles lying within qualification of the average amateur mechanic, is extremely limited. Performance of any works connected with need of dismantling and adjustment of components, and not listed below in this Chapter, should be entrusted to experts firm Citroёn company service center, or to mechanics of specialized car repair shop.

Precautionary measures

In order to avoid damages of components of system of a turbo-supercharging, do not begin movement right after engine start, especially in cold weather. Wait final stabilization of turns of idling, having given to oil within several seconds проциркулировать through turbokompressor bearings. Suppress the engine only after its turns will be dumped to single, - the podgazovka at the moment of switching off of ignition will force a wheel of the turbine to rotate for some time without greasing.

Observe the schedule of routine maintenance of the car, during time make replacement of impellent oil and the oil filter. A delay with change of oil or use of a substandard product can lead to formation of coal deposits on a shaft of the turbine and a premature exit of a turbokompressor out of operation.