Volvo 240/740/760/780/940/960 1990-1998

Bosch LH-Jetronic Fuel Injection System



LH denotes that this is a "hot wire" system. The system is fully electronically controlled and incorporate a number of sensors, whose signals are processed by a control unit. There are several different versions of the LH system, including the 2.2, 2.4, 3.1 and 3.2. The Bosch LH-Jetronic system is used in combination with the EZK ignition system and the turbocharged control system, where applicable. The LH fuel system is characterized by the following:

Measurement of intake air through the air mass meter of the hot wire type
Use of a separate cold start valve that supplies extra fuel, at or below 60°F (16°C)
Knock controlled fuel enrichment system
Engine speed taken from an inductive transmitter on the flywheel
Lambda probe (oxygen sensor) providing oxygen content of the exhaust gases
EVAP system to minimize evaporation from the fuel tank
Three-way catalytic converter

Several sensors feed the control unit information to precisely control fuel injection. To accomplish this, the control unit evaluates: exhaust gas oxygen content from the oxygen sensor (Lambda-sond), engine RPM and crankshaft position information from the ignition system control unit (if information is not received, the fuel system control unit will not function), engine temperature from the coolant temperature sensor, engine load information from the air mass meter, information from the throttle switch, which indicates if the throttle is closed or wide open, electrical system voltage from the battery current and signals from the A/C switch and clutch, indicating whether they are operating.