🚗 Classic Fault — Mercedes-Benz W115 (1968–1976)
Fuel pump diaphragm crack — pressure loss
💰 Estimated Repair Cost
$25 – $80 USD
Parts and labour estimate
🔧 Tools Required
Fuel container, basic tools
📋 Overview
The mechanical fuel pump diaphragm hardens and cracks with age causing low or intermittent fuel pressure. Fuel may also leak into the engine oil via the pump body.
🩺 Symptoms
- Engine cuts out under load
- hesitation at speed
- fuel smell from engine oil
- low power above 3000 RPM
🔍 Possible Causes
- Cracked or hardened fuel pump diaphragm
- worn rocker arm
🛠️ Diagnosis Steps
Test fuel pump delivery: disconnect outlet pipe into container, crank engine briefly. Flow should be strong and consistent.
✅ Most Confirmed Fix
Rebuild fuel pump with new diaphragm and valve kit.
80% of users confirm this fix worked (24 reports)
🏷️ Parts Needed
M115 fuel pump repair kit or replacement pump
🔗 Other Mercedes-Benz W115 Faults
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