Removed text is struck through; added text is highlighted.
What is D-Jetronic?
Bosch D-Jetronic is an early electronically controlled, intermittent port-injection system. Bosch lists its 1967 introduction on the VW 1600 E. Unlike K- and KE-Jetronic, its main injectors are solenoid valves opened in electrical pulses. Its ECU uses analogue electronic circuitry to determine injection duration; it is not a modern digital, map-based ECU. [1, 2]
Saab 2.0 B engine: the photographer identifies this 1973–74 engine as D-Jetronic-equipped. Photograph: Dougsaab / Wikimedia Commons, CC BY-SA 3.0; unmodified.
Simplified fuel and signal paths, drawn for this reference from Bosch's system layout and workshop description. It is a functional diagram, not a vehicle wiring diagram. Component arrangements and optional equipment vary. [3, 2]
How it works
An electric pump and filter supply a common fuel distribution pipe or rail. A pressure regulator controls fuel pressure and returns surplus fuel to the tank.A manifold-pressure sensor connected to the intake manifold supplies the main engine-load information. Distributor trigger contacts provide engine-speed and injection-trigger information.The ECU combines these inputs with corrections such as engine and intake-air temperature and throttle-switch signals. It produces electrical injection pulses whose duration varies with operating conditions.The electrically operated injectors spray fuel into the intake ports. In the documented four-cylinder VW-Porsche example, they operate in two pairs rather than as individually timed sequential injectors. [2]
The analogue pressure sensor and ECU
The pressure sensor is connected to the manifold by a hose. Its pressure-sensitive internal elements move an armature in a coil assembly, changing inductance in the ECU's analogue circuit; it is not simply a modern three-wire voltage-output MAP sensor. Designs and calibration differ, so match the sensor to the engine and ECU rather than assuming similar-looking parts interchange. [4]
The original system determines fuel from its inputs without the lambda-sensor feedback loop found on later closed-loop systems. An auxiliary-air device and, on documented installations, a separate electrically operated cold-start valve support cold running and starting. The exact control and components differ by model. [3, 2]
What kind of injectors?
D-Jetronic's main injectors are electromagnetic port injectors. The ECU energises each group of injector coils to lift the valves; fuel pressure forces fuel through while they are open. At the specified regulated pressure, the length of the pulse is a major determinant of the delivered quantity. The separate cold-start valve should not be confused with the main injector set. [2]
By comparison, K-Jetronic and KE-Jetronic meter fuel in a distributor and use pressure-opening continuous-spray main injectors. The presence of an electronic ECU does not by itself tell you which kind of injector is fitted.
Identification and workshop checks
Identify the engine, ECU, pressure sensor and injector part numbers as a matched application. A manifold hose leading to a separate pressure sensor, distributor trigger contacts and electrical injector connectors are useful clues.Check fuel hoses, leaks, pump supply and regulated pressure against the correct vehicle specification. Injector condition, leaks, spray and electrical connections affect fuel delivery; use the appropriate injector-testing procedure.Inspect the pressure-sensor hose and connections, engine and air temperature sensors, throttle switch, distributor trigger contacts, wiring, grounds and relays. Follow the correct manual's test conditions and limits.Do not turn sealed pressure-sensor adjustments as a first response to poor running. The sensor's calibration is application-specific; check for other faults and use a specialist procedure if it needs assessment.
Follow the applicable procedure to release fuel pressure before opening a line. The source-linked Bosch teaching sheet below provides a labelled visual layout.
Sources and further pictures
[1] Bosch Classic: spare parts brochure, Jetronic history and components.[2] Bosch D-Jetronic workshop manual, VW-Porsche 914, independent reproduction; system description, paired injectors and test charts. The described details are specific to that installation.[3] Bosch Classic: D-Jetronic teaching diagram, labelled system and air-cooled-engine layouts.[4] Dr-DJet: manifold pressure sensor, specialist description and photographs of sensor construction; application and calibration information should be checked against the relevant vehicle manual.Bosch historical photograph of an early Jetronic control-unit circuit board. Accessed 10 November 2026.
Page organisation changed
Field
Revision 1
Revision 2
Page type
ECU hub
ECU hub
Subject
ECUs
ECUs
Parent
Bosch
Bosch Jetronic
Applies to
No ECU-specific applicability
No ECU-specific applicability
Tool groups
Not recorded in this older revision
None
Vehicle makes
Not recorded in this older revision
None
Rendered revisions
Open each version to inspect formatting, tables and photographs.
Revision 1: Bosch D-Jetronic
What is D-Jetronic?
Bosch D-Jetronic is an early electronically controlled, intermittent port-injection system. Bosch lists its 1967 introduction on the VW 1600 E. Unlike K- and KE-Jetronic, its main injectors are solenoid valves opened in electrical pulses. Its ECU uses analogue electronic circuitry to determine injection duration; it is not a modern digital, map-based ECU. [1, 2]
Saab 2.0 B engine: the photographer identifies this 1973–74 engine as D-Jetronic-equipped. Photograph: Dougsaab / Wikimedia Commons, CC BY-SA 3.0; unmodified.Simplified fuel and signal paths, drawn for this reference from Bosch's system layout and workshop description. It is a functional diagram, not a vehicle wiring diagram. Component arrangements and optional equipment vary. [3, 2]
How it works
An electric pump and filter supply a common fuel distribution pipe or rail. A pressure regulator controls fuel pressure and returns surplus fuel to the tank.
A manifold-pressure sensor connected to the intake manifold supplies the main engine-load information. Distributor trigger contacts provide engine-speed and injection-trigger information.
The ECU combines these inputs with corrections such as engine and intake-air temperature and throttle-switch signals. It produces electrical injection pulses whose duration varies with operating conditions.
The electrically operated injectors spray fuel into the intake ports. In the documented four-cylinder VW-Porsche example, they operate in two pairs rather than as individually timed sequential injectors. [2]
The analogue pressure sensor and ECU
The pressure sensor is connected to the manifold by a hose. Its pressure-sensitive internal elements move an armature in a coil assembly, changing inductance in the ECU's analogue circuit; it is not simply a modern three-wire voltage-output MAP sensor. Designs and calibration differ, so match the sensor to the engine and ECU rather than assuming similar-looking parts interchange. [4]
The original system determines fuel from its inputs without the lambda-sensor feedback loop found on later closed-loop systems. An auxiliary-air device and, on documented installations, a separate electrically operated cold-start valve support cold running and starting. The exact control and components differ by model. [3, 2]
What kind of injectors?
D-Jetronic's main injectors are electromagnetic port injectors. The ECU energises each group of injector coils to lift the valves; fuel pressure forces fuel through while they are open. At the specified regulated pressure, the length of the pulse is a major determinant of the delivered quantity. The separate cold-start valve should not be confused with the main injector set. [2]
By comparison, K-Jetronic and KE-Jetronic meter fuel in a distributor and use pressure-opening continuous-spray main injectors. The presence of an electronic ECU does not by itself tell you which kind of injector is fitted.
Identification and workshop checks
Identify the engine, ECU, pressure sensor and injector part numbers as a matched application. A manifold hose leading to a separate pressure sensor, distributor trigger contacts and electrical injector connectors are useful clues.
Check fuel hoses, leaks, pump supply and regulated pressure against the correct vehicle specification. Injector condition, leaks, spray and electrical connections affect fuel delivery; use the appropriate injector-testing procedure.
Inspect the pressure-sensor hose and connections, engine and air temperature sensors, throttle switch, distributor trigger contacts, wiring, grounds and relays. Follow the correct manual's test conditions and limits.
Do not turn sealed pressure-sensor adjustments as a first response to poor running. The sensor's calibration is application-specific; check for other faults and use a specialist procedure if it needs assessment.
Follow the applicable procedure to release fuel pressure before opening a line. The source-linked Bosch teaching sheet below provides a labelled visual layout.
[4] Dr-DJet: manifold pressure sensor, specialist description and photographs of sensor construction; application and calibration information should be checked against the relevant vehicle manual.
Bosch D-Jetronic is an early electronically controlled, intermittent port-injection system. Bosch lists its 1967 introduction on the VW 1600 E. Unlike K- and KE-Jetronic, its main injectors are solenoid valves opened in electrical pulses. Its ECU uses analogue electronic circuitry to determine injection duration; it is not a modern digital, map-based ECU. [1, 2]
Saab 2.0 B engine: the photographer identifies this 1973–74 engine as D-Jetronic-equipped. Photograph: Dougsaab / Wikimedia Commons, CC BY-SA 3.0; unmodified.Simplified fuel and signal paths, drawn for this reference from Bosch's system layout and workshop description. It is a functional diagram, not a vehicle wiring diagram. Component arrangements and optional equipment vary. [3, 2]
How it works
An electric pump and filter supply a common fuel distribution pipe or rail. A pressure regulator controls fuel pressure and returns surplus fuel to the tank.
A manifold-pressure sensor connected to the intake manifold supplies the main engine-load information. Distributor trigger contacts provide engine-speed and injection-trigger information.
The ECU combines these inputs with corrections such as engine and intake-air temperature and throttle-switch signals. It produces electrical injection pulses whose duration varies with operating conditions.
The electrically operated injectors spray fuel into the intake ports. In the documented four-cylinder VW-Porsche example, they operate in two pairs rather than as individually timed sequential injectors. [2]
The analogue pressure sensor and ECU
The pressure sensor is connected to the manifold by a hose. Its pressure-sensitive internal elements move an armature in a coil assembly, changing inductance in the ECU's analogue circuit; it is not simply a modern three-wire voltage-output MAP sensor. Designs and calibration differ, so match the sensor to the engine and ECU rather than assuming similar-looking parts interchange. [4]
The original system determines fuel from its inputs without the lambda-sensor feedback loop found on later closed-loop systems. An auxiliary-air device and, on documented installations, a separate electrically operated cold-start valve support cold running and starting. The exact control and components differ by model. [3, 2]
What kind of injectors?
D-Jetronic's main injectors are electromagnetic port injectors. The ECU energises each group of injector coils to lift the valves; fuel pressure forces fuel through while they are open. At the specified regulated pressure, the length of the pulse is a major determinant of the delivered quantity. The separate cold-start valve should not be confused with the main injector set. [2]
By comparison, K-Jetronic and KE-Jetronic meter fuel in a distributor and use pressure-opening continuous-spray main injectors. The presence of an electronic ECU does not by itself tell you which kind of injector is fitted.
Identification and workshop checks
Identify the engine, ECU, pressure sensor and injector part numbers as a matched application. A manifold hose leading to a separate pressure sensor, distributor trigger contacts and electrical injector connectors are useful clues.
Check fuel hoses, leaks, pump supply and regulated pressure against the correct vehicle specification. Injector condition, leaks, spray and electrical connections affect fuel delivery; use the appropriate injector-testing procedure.
Inspect the pressure-sensor hose and connections, engine and air temperature sensors, throttle switch, distributor trigger contacts, wiring, grounds and relays. Follow the correct manual's test conditions and limits.
Do not turn sealed pressure-sensor adjustments as a first response to poor running. The sensor's calibration is application-specific; check for other faults and use a specialist procedure if it needs assessment.
Follow the applicable procedure to release fuel pressure before opening a line. The source-linked Bosch teaching sheet below provides a labelled visual layout.
[4] Dr-DJet: manifold pressure sensor, specialist description and photographs of sensor construction; application and calibration information should be checked against the relevant vehicle manual.
