General System Description

Fig. 2 Bosch L-Jetronic fuel injection system:

Bosch L-Jetronic electronic fuel injection system--Fig 2.
- Various sensors send signals to the ECU representing engine operating conditions.
- The ECU uses this sensor information to determine optimum fuel injector pulse width (injector open-valve time period).

This system is designed so that the mixture ratio can be precisely controlled to the stoichiometric point, allowing the three-way catalyst to minimize all types of exhaust emissions simultaneously. An oxygen sensor installed in the exhaust manifold indicates whether the mixture is too rich or too lean. The sensor transmits a nonlinear voltage to the control unit and the control unit adjusts the injection pulse width according to sensor voltage so the mixture ratio will be within the narrow window of the three-way catalyst. During engine warm up this system is open until the sensor reaches operating temperature.