Let’s drive into the world of vintage Bosch fuel injection systems and understand what are CIS Injectors. Let’s break it down:
Overview
Bosch developed several major types of early electronic and mechanical fuel injection systems from the 1960s–1980s. The three you mentioned — CIS, K-Jetronic, and L-Jetronic — are related but quite different in how they deliver fuel.
CIS (Continuous Injection System) — aka K-Jetronic
How it works:
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CIS = Continuous Injection System, Bosch’s name for K-Jetronic.
So technically, CIS and K-Jetronic are the same thing. -
It is a mechanical fuel injection system.
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Fuel is continuously sprayed into each intake port — not pulsed electronically.
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A fuel distributor and airflow sensor plate mechanically meter fuel based on air intake.
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Later variants (like KE-Jetronic) added electronic control for fine adjustments.
Injector type:
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Mechanical injectors — they’re spring-loaded nozzles that open at a set pressure (no electrical connector).
Cars that used it:
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Volkswagen Golf/Rabbit, Jetta, Scirocco (1970s–mid-80s)
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Porsche 911, 924, 928
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Mercedes-Benz (late 1970s–1980s)
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Volvo 240, 740 (some variants)
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Audi 4000/5000 (early models)
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Saab 900 (early models)
K-Jetronic (by name)
As mentioned, this is the Bosch CIS.
But it’s worth noting there were several subtypes:
| Version | Type | Years | Notes |
|---|---|---|---|
| K-Jetronic | Mechanical | 1973–85 | Basic continuous injection |
| KE-Jetronic | Electro-mechanical | mid-1980s–early 1990s | Adds electronic control of fuel mixture |
L-Jetronic
How it works:
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L-Jetronic is a fully electronic, pulsed fuel injection system.
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Uses an airflow meter (vane-type) to measure incoming air.
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An ECU (computer) calculates injection time based on sensors (air temp, throttle position, coolant temp, etc.).
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Fuel is injected in pulses rather than continuously.
Injector type:
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Electronic solenoid injectors — each has a connector and opens when the ECU sends a pulse.
Cars that used it:
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BMW 320i (E21, late ’70s)
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Datsun/Nissan 280Z, 280ZX
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Alfa Romeo Spider (1982+)
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Fiat, Lancia models
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Volvo 240 (certain B21F engines)
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Volkswagen Type 2 (Bus), Type 3, Beetle (late EFI models)
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Porsche 914 1.8 (mid-’70s)
Summary Table
| System | Type | Injector | Injection Mode | Control | Typical Era | Example Cars |
|---|---|---|---|---|---|---|
| CIS / K-Jetronic | Mechanical | Pressure-opened (no electrical connection) | Continuous | Mechanical | 1973–1985 | VW, Porsche, Mercedes, Audi |
| KE-Jetronic | Electro-mechanical | Same injectors, with electronic pressure control | Continuous | Partial ECU | 1985–1992 | Mercedes, Volvo, Saab |
| L-Jetronic | Electronic | Solenoid, ECU-controlled | Pulsed | Full ECU | 1974–1985 | BMW, Datsun, Alfa Romeo, VW |
