First, never trust the ``no serviceable parts inside'' sign, it's
a conspiracy by the auto manufacturers to keep you poor and dumb.
L-jetronic is a Bosch-manufactured electronic fuel injection featured on
many early 80's cars. The basic L-jetronic consists of a Fuel pump,Fuel filter,
Fuel lines, Fuel regulator, Fuel injectors, Cold-start injector (Could be omitted on some L's), Thermo-time switch, Coolant temperature sensor, auxiliary air valve, throttle plate and an air-flow sensor (Flap type in analog L's discussed here).
Also included may be an assortment of different sensors.
- Air flow sensor. Used by ECU (Electronic Control Unit) to measure intake air flow, uses logarithmic scale, Max airflow = 30 x min.
- Coolant temperature. Used by the ECU to determine the amount of enrichment for a cold engine.
- Lambda sensor. Used by the ECU to keep the air-fuel ratio at lambda=1.
- Idling and Wide-Open-Throttle switches. Located in the axle of the intake throttle flap, used by the ECU for fuel-cutoff and WOT enrichment (approx. 9%)
- Thermo-time switch. Not really an sensor, drives the Cold-start injector.
- Cold-start injector. Not in all L's, opens when the engine is cold.
- Auxiliary air valve. Keeps the revs up when engine is cold. Closes either
by engine heat or the heat from the internal heating element. Can be water-heated (BMW's).
- Throttle plate. Used to control the airflow into engine.
- Fuel pump. High pressure pump to supply the fuel to injectors, operated by electricity.
- Fuel pressure regulator. Used to keep the pressure between manifold vacuum and outside air constant.
The bread and butter:
- ECU. Controls the injector on-time based on air-flow sensor and other sensors. Lambda-control seems rev-dependent.
- Injectors. Spray the pressurized fuel into manifold.
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