This is a relatively common problem. There might be an issue with the filler neck where a tab bends and impedes the cap to be unscrewed.A new cap won't solve the problem. IMPORTANT NOTE;.
Genuine OEM MERCEDES-BENZ W124 1984-96 CLIMATE VALVE ACTUATOR VACUUM
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REAL GENUINE OEM Mercedes BENZ Fuel Gas Tank Cap 2154700105
15 New Genuine OEM Mercedes-Benz Grill Retainer Fasteners (15 pcs.) 0029885181
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