🚗 Classic Fault — Mercedes-Benz W115 (1968–1976)
Automatic choke bimetal spring fatigue
💰 Estimated Repair Cost
$15 – $50 USD
Parts and labour estimate
🔧 Tools Required
Multimeter, screwdrivers
📋 Overview
The bimetal spring in the automatic choke housing weakens over decades, failing to provide sufficient closing force in cold conditions. The choke flap opens too quickly, causing lean mixture and hard cold starts.
🩺 Symptoms
- Hard starting when cold
- engine fires but immediately stalls
- needs excessive throttle pumping when cold
🔍 Possible Causes
- Fatigued choke bimetal spring
- choke housing electrical heater failure
- incorrect choke adjustment
🛠️ Diagnosis Steps
Check choke flap position before starting cold engine — should be nearly closed. Test choke heater element resistance: should be 40-60 ohms.
✅ Most Confirmed Fix
Replace choke bimetal spring or complete choke housing. Adjust choke index marks.
80% of users confirm this fix worked (20 reports)
🏷️ Parts Needed
Zenith choke bimetal spring; choke cover assembly
🔗 Other Mercedes-Benz W115 Faults
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