Computers and Control Systems: Description and Operation

Fig. 1 Bosch CIS fuel injection system W/Lambda control:

Bosch K-Jetronic (CIS) fuel injection is a hydraulically operated continuous injection system which uses intake air flow to control the amount of fuel supplied to the fuel injectors and an oxygen sensor feedback circuit to provide precise control of air/fuel mixtures. Basic CIS components include the mixture control unit, (which combines an air flow sensor and fuel distributor), separate injectors for each cylinder, a cold start valve and thermo time switch, throttle bypass valve, control pressure (warm up) regulator, fuel pressure regulator and electric supply pump.
The oxygen sensor circuit includes a sensor which monitors exhaust gas oxygen content, sensors which monitor engine and vehicle operating conditions, a control module which monitors sensor inputs in order to compute ideal air/fuel mixtures for proper engine operation, and a frequency valve which controls fuel delivery to the injectors based on operating signals from the control module.