Skoda Felicia

since 1994 release

Repair and operation of the car



Skoda Felicia
+ Cars of the Skoda Felicia brand
+ Maintenance instruction
+ Routine maintenance
+ Repair of the engine
+ Cooling systems, heating
- Power supply system
   + Power supply system of the carburetor engine of 1.3 l
   - System of the central injection (SPFI) of the petrol engine
      General information and precautionary measures
      Removal and installation of assembly of the air cleaner
      The vacuum switch of the control unit temperature of the soaked-up air
      Removal, installation and adjustment of a cable of an accelerator
      Removal and installation of components of the Bosch Mono-Motronic system
      Removal and installation of assembly of a gasoline pump and sensor of fuel consumption
      Removal and installation of the fuel tank
      Dumping of residual pressure in a power supply system
      Removal and installation of the inlet pipeline
      Check of functioning and adjustment of system of injection
      Unleaded fuel - the general information and rules of use
   + System of the distributed injection (MPFI) of the petrol engine
   + Power supply system of the diesel engine
   + Systems of decrease in toxicity and production of the fulfilled gases
+ Engine electric equipment
+ Coupling
+ Transmission
+ Power shafts
+ Brake system
+ Suspension bracket and steering
+ Body and finishing of salon
+ Onboard electric equipment





System of the central injection (SPFI) of the petrol engine

General information and precautionary measures

Function chart of the Mono-Motronic system

1 — Mzamok of ignition
2 — the Rechargeable battery
3 — the Sensor of frequency and the provision of a bent shaft
4 — the l-probe
5 — the Catalytic converter
6 — the Coal adsorber
7 — Em the valve of system of catching of fuel evaporations
8 — the Fuel tank
9 — the Electric fuel pump
10 — the Fuel filter
11 — the Sensor of provision of a butterfly valve
12 Sensor of temperature of cooling liquid

13 — the Air cleaner
14 — a fuel injection Injector
15 — the fuel pressure Regulator
16 — the air temperature Sensor
17 — the Step engine of system of idling
18 — the Spark plug
19 — the ignition Distributor
20 — ECU of management of ignition
21 — ECU systems of injection
22 — Safety locks and the relay
23 — the Diagnostic socket


Scheme of functioning of an injector of injection and regulator of pressure of fuel

1 — a fuel Supply from a gasoline pump
2 — an injection Injector

3 — the fuel pressure Regulator
4 — Return of fuel to a tank


The Bosch Mono-Motronic system concerns to family of control systems of the engine of the closed type. Such systems exercise control as directly over fuel injection, and over its ignition.

The function chart of the Mono-Motronic system is submitted on an illustration. The main components of system of injection are among: the fuel tank with the submersible electric gasoline pump established in it, the fuel filter, lines of giving and return of fuel, the throttle case with the electronic injector of injection of fuel which is built in in it, and also an electronic control unit (ECU) complete with information sensors, actuation mechanisms and a connecting electrical wiring.

The gasoline pump provides continuous supply of fuel via the filter of cartridge type in the throttle case under small excessive pressure. The regulator of pressure of fuel which is built in the throttle case provides a constant pressure on an injection injector. Excess of fuel on the returnable line comes back to the fuel tank. Such system of continuous giving allows to reduce temperature of fuel and to prevent its evaporation.

Opening and closing of an injector is made at the command of ECU calculating the moment and duration of injection on the basis of the analysis of the arriving information signals of engine turns, situation and speed of movement of a butterfly valve, temperature of the soaked-up air, temperature of cooling liquid, speed of the movement of the car, composition of the fulfilled gases, etc. On an illustration the scheme of functioning of an injector of injection and the regulator of pressure of fuel is submitted.

The air which is soaked up in the engine passes through the air cleaner in which the filtering element made of dense paper replaceable is established. Temperature of the soaked-up air is regulated by means of the vacuum valve installed in an inlet sleeve of the air cleaner and allowing to mix external air with arriving through the heater casing placed over a final collector. The thermosensitive sensor switch installed in the air cleaner operates position of the gate of the valve.

Information on turns of the engine comes to ECU from the sensor of Hall established from above on a case of the transmission and fixing the frequency of rotation of a flywheel.

Temperature of the throttle of air coming to the case is taken by the sensor installed directly over an injection injector. Information comes to ECU which on the basis of its analysis defines the current requirements of the engine concerning the moment of injection and composition of air-fuel mix.

Control of turns of idling of the engine is exercised of partially electronic module of provision of a butterfly valve installed from above on the throttle case, and partially - system of ignition, due to change of installations of a corner of an advancing of ignition. In view of told need for manual corrections of turns disappears and an opportunity of system is not provided by its design. Information on situation and speed of movement of a butterfly valve is delivered in ECU by the special sensor sometimes called also by a potentiometer of a butterfly valve. The sensor is located on the left wall of the case of a throttle.

Content of oxygen in the fulfilled gases continuously is traced by ECU via the l-probe installed in forward section of system of release. Analyzing the arriving information, ECU issues commands for correction of a corner of an advancing of ignition and duration of injection, forming thereby air-fuel mix, optimum on structure. As a result, need for manual correction of contents WITH in the fulfilled gases also disappears. The catalytic converter is included in a basic equipment of all models considered in the present manual.

In addition to the listed functions, ECU exercises control of functioning of system of catching of fuel evaporations.

It is necessary to notice that failure diagnostics of the Bosch Mono-Motronic system is possible only by means of the special electronic reader. The diagnostic socket for connection of the reader is located in the right part of the dashboard of the car. In case of any violations of functioning of system it is necessary to address immediately experts company service center of the Skoda company which will make reading and interpretation of the ECU codes of the malfunctions revealed by system of self-diagnostics which are written down in the block of memory.

The replacement procedure of the refused components of system is described in the following Sections of the Head.

Precautionary measures

Gasoline is flammable liquid in the highest measure. When performing service of components of a power supply system it is necessary to observe special precautionary measures!


Do not smoke and do not approach the venue of works with a source of an open flame / the carrying unprotected by the lamp shade! You do not make service of components of a power supply system in the rooms equipped with the heating devices using natural gas and equipped with a control torch. You watch that near at hand constantly there was a charged fire extinguisher.

Avoid hit of fuel in eyes and on open sites of skin. Put on protective gloves and glasses. Wash away incidentally got splashes water with soap.
Remember that fuel evaporations not less if no more, are dangerous, than actually liquid fuel. Do not forget that the emptied container from under gasoline continues to contain the fuel vapors which are not only easily flammable, but also potentially explosive!

Many of the procedures described in this Chapter are connected with need of a detachment of fuel lines, inevitably leading to fuel pouring. Try to prepare beforehand all necessary materials for collecting the spilled fuel.

Remember that residual pressure continues to be present at a path of system later even long time after an engine stop. Before removal or a detachment of any of components of a fuel path this pressure needs to be dumped safely (see the Section Dumping of Residual Pressure in a power supply system).

Carrying out service of components of a power supply system pay special attention to respect for purity - hit to the fuel highway of dirt is capable to lead to violation of its passability leading to interruptions in operation of the engine and even to its spontaneous stops.

For the benefit of personal security of the performer and for safety of the equipment many of the procedures described in the present Chapter have to be made only after a detachment from the battery of a negative wire. Such precautionary measure first of all excludes a possibility of short circuit, and secondly, allows to avoid power surges in chains of an electronic part of a control system of the engine, many of components of which (such as ECU, sensors and actuation mechanisms) in the highest measure are sensitive to the overloads connected with such jumps.

Let's notice, however, that the system wants the known flexibility allowing it to adapt to the changes of characteristics of the engine connected with its wear in use of the vehicle. Such adaptability is connected with existence in memory of ECU of certain parameters. At shutdown of the battery this information is erased and after start of the engine its restoration demands small expenses of time. The rehabilitation period can be followed by violation of stability of turns of the engine, decrease in sensitivity to change of provision of a butterfly valve, easy increase in fuel consumption, etc. Duration of recovery process is defined by the frequency of use and service conditions of the vehicle.