The car will probably start without several GP's working in warm to hot weather, but it will place a greater strain on the starter and the battery as things continue to deteriorate. The battery, starter, and compression all have to be good in order for the engine to sucessfully start. Temperatures above 50F also help. The GP replacement probably sounds like a formidable job, but it is really the best route and you will learn a lot about the engine in the process.

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1961 190Db retired
1968 220D/8 325,000
1983 300D 164,150