🚗 Classic Fault — Mercedes-Benz (1976–1985)
W123 300D OM617 injection pump timing drift
💰 Estimated Repair Cost
Up to $150 GBP
Parts and labour estimate
🔧 Tools Required
Dial indicator, injection timing tools
📋 Overview
The mechanical injection pump on the OM617 five-cylinder slowly drifts out of timing, degrading economy and power.
🩺 Symptoms
- Gradual loss of power over months
- increased black smoke
- harder hot starting
- rattly diesel knock
🔍 Possible Causes
- Injection pump timing drift
- worn pump drive gear
- air in fuel system
🛠️ Diagnosis Steps
Check pump timing with dial indicator on number 1 injector — compare to spec. Timing marks on pump flange
✅ Most Confirmed Fix
Injection pump timing adjustment
78% of users confirm this fix worked (22 reports)
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