D-Jetronic Fuel Injection Issues (1970-1973)
Symptoms
Rough idle, hesitation on acceleration, hard cold starting, surging at steady throttle, and inconsistent fuel mixture.
Cause
The Bosch D-Jetronic system was one of the earliest electronic fuel injection systems fitted to a production car. It uses pressure sensors, temperature sensors, and analogue electronic circuitry to control fuel delivery. After 50+ years, the electronic components degrade: the ECU's internal capacitors fail, the pressure sensor loses calibration, the injectors clog or leak, and the wiring harness develops resistance from corroded connections.
Fix
Systematically diagnose and replace failed components.
Rebuilt ECUs are available from specialist suppliers.
New-manufacture injectors are available.
The wiring harness should be inspected and repaired or replaced.
Some owners convert to later L-Jetronic or aftermarket programmable injection, which is more reliable but not period-correct.
Cost: $500-$2,000 for D-Jetronic restoration, $1,500-$3,000 for conversion to aftermarket injection.
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