Citroën Xantia

since 1993 release

Repair and operation of the car

Power supply system - diesel models

General information

Assembly of the thermostat / fuel filter

Components of a power supply system are among: the fuel tank installed in a back part of the car, the fuel filter with the built-in moisture separator, the fuel pump of high pressure (FPHP), nozzles of injection of fuel and the accompanying elements. Before passing through the filter, fuel is warmed up through a run of cooling liquid of the engine through the basis of a casing of thermostat/assembly of the filter (see the filter illustration Assembly of the Thermostat / Fuel). Intensity of heating is defined by ambient temperature. If temperature of air makes less than 15 °C, the thermostatic element rises from situation "and", fuel arrives via with the union, passes through an opening of "d", is warmed up, passing through "e" and "b" channels and is brought to the filter. At air temperature from 15 °C to 35 °C the valve of the thermostat opens only partially, at the same time only a part of fuel passes directly from "with" to "b". The system of a turbo-supercharging which compressor is equipped with the built-in cooler (Intercooler) is included in the additional package of some models.

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

Arrangement of the TNVD external components of the Lucas system

Arrangement of the TNVD external components of the Bosch system

TNVD rotates with a frequency equal to a half of frequency of rotation of a bent shaft, and is put in action from a gas-distributing belt. Tightening of fuel to the high pressure at which its successful mixing with compressed air in vortex cameras is guaranteed in TNVD of the Bosch system is made by means of the cam plate putting the only piston in action. In pumps of production of Lucas (CAV) two opposing pistons squeeze the volume which is between them at the expense of the rollers rotating in a cam ring. Further fuel passes through the central rotor with the only output drilling combined with the ports conducting to tubes of nozzles (see the illustrations Arrangement of the TNVD External Components of the Lucas System and Arrangement of the TNVD External Components of the Bosch System ).

Management of a dosage of the given fuel is made by the centrifugal regulator reacting to position of the accelerator pedal and turns of the engine. The regulator is connected to the dosing valve which makes correction of amount of injectable 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 in pressure of pressurization.

Basic installation of phases of gas distribution is made at installation of the pump. In operating time of the engine the mechanism of rotation of a cam plate / ring automatically corrects parameters for the purpose of achievement of maximum efficiency of return of the unit.

Four nozzles make injection of uniform streams of fuel in the vortex cameras located in a head of cylinders. Nozzles are calibrated so that to open and be closed with certain critical pressure that guarantees maximum efficiency and uniformity of combustion of mix. The operating needles of nozzles are greased with the arriving fuel collecting in spring cameras and then coming to a returnable hose of TNVD on by-pass tubes.

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

Efficiency of cold start increases due to preliminary heating, or by means of the incandescence candles installed in vortex cameras. The thermosensitive sensor of the cooling system operates the lever of turns of bystry idling on TNVD, providing increase in 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 with cooling liquid capsule.

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

Functioning of a turbocompressor is carried out due to energy of the fulfilled gases. Gases pass a casing (a turbine casing) through a special form, putting a turbine wheel in action. The wheel is fixed on a shaft on which other end the second scapular wheel called by a compressor wheel is located. The wheel of the compressor rotates in own casing and carries out compression of the soaked-up air given then in the inlet pipeline.
On the way from a turbocompressor to the inlet pipeline air passes through the special built-in cooler (Intercooler) representing the heat exchanger functioning according to the scheme "air-air" and installed near an engine cooling system radiator. Cold air is delivered to the heat exchanger of the built-in cooler by the running flow created due to the movement of the car counter. A problem of a cooler is selection of the surplus of heat which is formed when tightening air in a turbocompressor. At the same time 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 due to functioning of the special waste gate making removal of the fulfilled gases from a turbine wheel 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 by the motive oil given under a pressure on a special tube. The lubrication system is arranged in such a way that the shaft is hung out on an oil pillow. Further oil on a returnable tube goes back to the engine case pallet. On some models additional security measures against a turbine overheat, due to its connection with a path of the cooling system of the engine are taken.

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

The range of procedures of service of TNVD and 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 which are not listed below in this Chapter has to be entrusted to experts company service center of the Citroyon company, 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 the movement right after start of the engine, especially in cold weather. Wait for final stabilization of turns of idling, having allowed oil to protsirkulirovat within several seconds through turbocompressor bearings. You suppress the engine only after its turns are dumped to single, - the podgazovka at the time of switching off of ignition will force a wheel of the turbine to rotate without lubricant for some time.

Observe the schedule of routine maintenance of the car, in time you make replacement of motive oil and an oil filter. The 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 turbocompressor out of operation.