BOSCH LH-JETRONIC - Engine Control System: Description

The Volvo Computerized Engine Control System is used on all Volvo 4-cylinder engines except GLT Turbo. It consists of a computer controlled electronic ignition system and Bosch LH-Jetronic II fuel system with integrated Constant Idle Speed system.

The computer controlled ignition system consists of Volvo breakerless distributor, an electronic control unit, ignition coil, ignition switch, throttle switch and knock sensor. The distributor contains no vacuum or centrifugal advance mechanisms. The rotor and armature are a single unit. See Fig 1 .

Fig 1: Disassembled View of Volvo Electronic Distributor Distributor contains Hall sending unit.

A Hall Effect sending unit in the distributor provides engine speed signals to the electronic control unit. The distributor also consists of necessary connecting wiring and a distributor cap.

The fuel system includes an electronic control unit, ignition coil, ignition switch, system relay, fuel system components, A/C switch, airflow meter, air control valve, starter motor, throttle switch, coolant temperature sensor, oxygen sensor and connecting wiring and hoses.

NOTE: Only those components directly used in the Constant Idle Speed system will be covered in this section. For information on fuel injection system, refer to appropriate article in FUEL SYSTEMS section.

Fig 2: Volvo Computer Controlled Ignition System