Jetronic

Jetronic is a form of engine management, responsible for controlling the fuelling and occasionally the ignition of early E30 engines. It was superceded by Motronic in 1987.

Overview

Jetronic is an analogue engine management system which uses a number of sensors to measure the condition and performance of the engine in order to manage fuelling, all controlled by a simple ECU. Ignition timing is governed by a mechanical distributor, which was regulated by a number of mechanisms to advance or retard timing. The ignition timing is completely separate from the fuelling, unlike the later Motronic management which combined these two features.

A number of Jetronic versions were fitted to the E30 during its build. The earliest models, from late 1982 to early 1983, were equipped with K-Jetronic; a purely mechanical fuel injection system with a rudimentary transistor-based ignition. This technology had been carried over from the E21, who shared the same M10 and M20 engines with the E30. However, none of these models were available in RHD, so very few are seen on UK roads.

LE-Jetronic quickly replaced K-Jetronic, and is the most commonly used Jetronic system in the E30. Often referred to as simply L-Jetronic, the E stands for Economy and highlights the systems focus on fuel efficiency over power. The system went through a revision during its production years, meaning that a variety of components were used to solve issues such as idling and cold starting.

While Jetronic was originally a very practical system, decades of use is rendering Jetronic setups more and more inefficient and unreliable due to their reliance on mechanical and vacuum-driven components which can wear out over time. For that reason, we recommend converting to Motronic 1.3.

Versions

K-Jetronic

M60 engine with K-Jetronic

K-Jetronic is a mechanical fuel distribution system, and does not need an ECU to control it.

The basic concept is that a fuel distributor is charged with fuel from the fuel pump, up to 5 bar. From there, individual pipes run to each cylinder where a spring-loaded nozzle acts as injectors. The fuel distributor is directly connect to an air intake meter; an air flap that rises and falls with the flow of air into the engine. As the flap rises due to increased air flow, it also opens up the flow through the fuel distributor allowing more fuel to be pumped through to the spray nozzles. When the fuel pressure is high enough to overcome the springs in the nozzles, fuel is sprayed into the engine.

K-Jetronic systems can therefore be identified by the snake of pipework running over the intake manifold, and the large mechanical fuel distributor bolted to the left hand inner wing in the engine bay.

M20 engines fitted with K-Jetronic were known as M60 engines, not to be confused with the later M60 V8 engines.

LE-Jetronic

LE-Jetronic

Components

The following components are specific to Jetronic-equipped vehicles. The information here supercedes any other details of components outlined in the Wiki, especially regarding Ignition, Fuel and Intake.

ECU Codes

ECU Number	System	Models	From/To
0280 000 310	LE-Jetronic	318i with cat.	1983 - 84
0280 000 318	LE-Jetronic	318i	1983 - 84
0280 000 330	LE-Jetronic	318i	1984 - 87
0280 001 301	LE-Jetronic	320i and 323i	1982 - 84
0280 001 309	LE-Jetronic	Later 320i	1984 - 87
0280 001 308	LE-Jetronic	Later 323i	1984 - 86