First, never trust the 'no serviceable parts inside' sign, it's a conspiracy
by the auto manufacturers to keep you poor and dum.
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 (appx. 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.
- 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:
This is all common knownledge, move to the mods section
- 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.