The basic K-Jetronic system consists of: an air flow meter to monitor the volume of air entering the engine; fuel distributor, composite with air flow meter; cold start valve and auxiliary air device for starting a cold engine; warm-up regulator. The cold start fuel supply mode switch activates the cold start valve during the initial cold start for a period depending on the engine temperature.
The KE-Jetronic system uses the same basic system, but also has sensors that monitor engine speed, load and temperature. The signals from the sensors are processed by an electronic control unit (ECU), which includes a fuel pressure control unit in the fuel rail. This maintains the pressure of the fuel pumped by the injectors. If the electronic system fails with a warm engine, the system will operate as a K-Jetronic, thus allowing the car to drive home.
Multi-Point Injection (MPI) is a fully electronic engine management system that uses sensors to monitor engine speed, load, and temperature.
The Mono-Jetronic system consists of a single injector unit mounted on the intake manifold like a carburetor. Electronic sensors monitor engine speed, load and temperature, and the signals are processed by an electronic control unit, as in the KE-Jetronic system.
Because of the complex electronic circuitry in many of these systems, certain precautions must be taken to prevent damage.
- (a) Do not disconnect the battery while the engine is running
- (b) Do not use the charger to start the vehicle
- (c) Do not disconnect the wiring with the ignition on
- (d) Remove the control unit if the temperature exceeds 80°C, such as when hot painting
- (d) Before checking the compression in the engine cylinders, disconnect the fuel pump control relay
The work described in the following Chapters is recommended to be carried out by home mechanics, and in case of significant damage, contact an Audi dealer.
