Short squirts of starting fluid will not do major or minor damage to the 617 engine. Nor is it likely to be a filter or bad fuel. More likely bad glow plugs. Is your glow plug light coming on before your start the car? Even if it is coming on, there could be one or more bad plugs. do a search in diesel discussion for glow plugs. Plenty of information there.

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1984 300SD 326,997 miles and counting . . . No wait, my odometer is still dead