1959 Mercedes Benz 180 Diesel W120 Ponton does not start...ideas?

UPDATE, glowplugs worn out ,
New battery, rebuilt starter n solenoid, does not start , u can put screwdriver on hot terminal on starter n hit other end to ground n solenoid cranks,, so its switch or something else..If u can post your ideas to get it to crank, let me know ,will service the diesel compressor parts next ,..looking to buy Porsche speedster, cabriolet , coupe, any condition, 911s 356, 912,
also looking to buy ww2 Zundapp ks750 ks600 BMW r75 n other ww2 bikes
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