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About the K-Jetronic Injection System

This rather extensive article covers all aspects of the K-jetronic fuel injection systems found in E21's, such as the 318i, 320i and the 323i. Reading through these pages will help you understand how this system works, what it does, and it's individual parts.
The content of this article is a general description of the K-jetronic system, as it was used in many other cars and many other engines. Consider this as vital background information if your E21 runs with K-jetronic.

Since their introduction, the Jetronic fuel injection systems have proved themselves millions of times over under the harsh conditions of everyday driving. This success is a result of the advantages which fuel injection can offer when considering today's demands for economy, performance, and cleaner exhausts. The K-Jetronic is a mechanical system in which the fuel is continuously metered in accordance with the amount of air drawn in by the engine. Using the Lambda sensor together with additional equipment for the Lambda closed-loop control facility, the K-Jetronic can already comply today with the exhaust-gas regulations of tomorrow. The construction and principle of operation of the K-Jetronic is dealt with in this Technical Instruction manual.
Edited by Bob Isaac

Page 1
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The engine's fuel requirements:
Air-fuel ratio
Excess-air factor

Fuel-management systems:
Electronically controlled systems
Mechanical systems


Fuel supply:
Outline of system
Electric fuel pump
Fuel accumulator
Fuel filter
Primary-pressure regulator
Fuel-injection valve
Page 2
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Fuel management:
Mixture-control unit
Air-flow sensor
Fuel distributor
Control pressure
Differential-pressure valves
Mixture information

Mixture adaptation:
Cold start
Load conditions
Acceleration response
Influencing the air-fuel mixture

Page 3
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Electrical circuitry:

Exhaust-gas techniques:
Exhaust-gas composition
Catalytic after-treatment
Lambda closed-loop control

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