Audi 80/Avant (B4)

since 1991-1995 release

Repair and operation of the car

Audi 80/Avant
+ Technical specification
+ Engines
+ System of production of the fulfilled gases
+ Cooling system
+ Fuel tank and fuel pump
+ Air filter and airintaking channels
- System of injection
   - System of injection of Mono-Motronic
      Operating procedure
      Malfunctions and independent diagnostics
      Independent repair
      Visual check
      Check of separate elements
      Check of the mode of idling and analysis of exhaust gases
      Check of catalytic converter and lambda probe
      Hummock drive of "gas"
      List of malfunctions
   + System of injection of Digifant
   + System of injection of KE-III-Jetronic
   + Systems of injection of MPI and MPFI
+ Coupling
+ Transmission and transmission
+ Suspension bracket and steering
+ Brake system
+ Anti-blocking system of brakes
+ Wheels and tires
+ Body electrical system
+ System of ignition
+ Lighting
+ Signalling devices
+ Devices and auxiliary devices
+ Heating and ventilation
+ body Elements
+ Search of malfunctions
+ Specifications

System of injection of Mono-Motronic

Function chart of system of injection of Mono-Motronic


In drawing the vpryskny nozzle (2) with even the connected plug (1), taken from a nest (3) blocks of preparation of gas mixture is shown. Sideways on the valve the fuel strainer is visible.

The disassembled pressure regulator:

1 – cover;
2 – spring;
3 – membrane;
4 – basic surface.

The regulator of provision of a butterfly valve (1) can be removed separately. It is necessary if the driving pusher of the switch of a signal of idling is faulty (2). The position (3) designates a persistent bolt of a butterfly valve.

The potentiometer of a butterfly valve is established and regulated at plant and it cannot be sorted. We only removed it to show you the sliding contacts and the carrying-out paths. In case of malfunction it is necessary to replace the block of preparation of gas mixture.

Central injection

The smallest Audi engine is equipped with system of injection of gasoline through one nozzle and a butterfly valve, so-called Mono-Motronic system. It consists generally of the case similar to the case of the carburetor and supplied with the one and only vpryskny nozzle. The fuel exit from a nozzle is regulated by the electronic control unit which at the same time provides management of regulation of an advancing of ignition.

Basic elements

Control unit

He is located in feet of the forward passenger in front of the heating channel and via the multicontact plug receives information from the following knots:

  • The Hall sensor in the ignition distributor – about the frequency of rotation of the engine.
  • Lambda probe in catalytic converter – about the content of residual oxygen in the fulfilled gases.
  • Potentiometer – about the provision of a butterfly valve and by that amount of the arriving air.
  • The sensor of temperature of the arriving air on an entrance of the block of preparation of gas mixture – about temperature of the arriving air.
  • Temperature sensor on a branch pipe of cooling liquid at the left on a head of the block of cylinders – about temperature of cooling liquid.

Processing the entering signals the control unit counts duration of opening of a vpryskny nozzle with the electromagnetic drive and by that amount of injectable fuel. Thus the control unit uses multiparameter characteristics of the engine – the file in which all possible conditions of the engine are written down. In the same place in the form of electric signals the data on amounts of fuel relating to this or that situation are written down. In addition in the form of characteristics in Mono-Motronic the indicators of the moments of ignition relating to amount of fuel and an operational situation are kept.

Butterfly valve

It is located at the very bottom of the block of preparation of gas mixture and regulates amount of air which the engine has to receive.

Extent of opening of the gate is defined by the driver when pressing an accelerator pedal. The pedal and a butterfly valve are directly connected with each other by means of the hummock drive of an accelerator.

Block of preparation of gas mixture

The majority of details of the central system of injection of gasoline are collected in this case. Passes the arriving air through it, and here – by means of a nozzle – fuel, as well as in the carburetor is added.

Vpryskny nozzle

It opens by means of an electromagnet. Thus fuel can arrive – or not – depending on a signal from the control unit. For optimum dispersion of fuel the nozzle is supplied with slanted outlets via which gasoline gets on a conic wall of the outlet, swirling there.

The Vpryskny nozzle can only open and be closed, but is not able to dose amount of fuel. Therefore its regulation happens on injection time. It is carried out as follows: the nozzle injects once at each impulse of a high-tension current from the Hall sensor. If a small amount of fuel is required, the nozzle opens at this impulse only for a short time – frequent well, than on one thousand seconds. If the engine needs more fuel (at cold start or full loading), injection happens during more long time. And so at each impulse of the sensor of the Hall.

The sensor of temperature of the arriving air

It is located sideways on the case of a nozzle and thus can precisely determine air temperature, the preparation of gas mixture coming to the block.

Pressure regulator

The fuel pump under pressure gives gasoline to pressure regulator which provides intake of gasoline to a nozzle under the same pressure of 0,8 - 1,2 bars. For this purpose he allows most or smaller part of gasoline to go back to a fuel tank on the drain highway. Giving via the fuel filter remains almost constant.

Regulator of provision of a butterfly valve

The small electric motor with angular transfer moves a driving pusher closer or farther from an emphasis of idling of a butterfly valve. Thus, depending on a situation the butterfly valve can open at a big or smaller size.

Thanks to it the frequency of rotation of idling remains to a constant at various loadings. Ahead in a driving pusher of the regulator of provision of a butterfly valve the so-called switch of a signal of idling which reports to the control unit if you release an accelerator pedal is located. This signal is necessary for stabilization of frequency of rotation of idling.

Potentiometer of a butterfly valve

He reports to the control unit about the movements of a butterfly valve and its situation. So, for example, fast opening of a butterfly valve is distinguished as acceleration of the car. If you take away a foot from an accelerator pedal, the signal of closing of a butterfly valve activates interruption in supply of fuel in the idling mode. The message passes in a type of an electric signal – the potentiometer represents not that other as variable resistance.