Springs are heat treated a certain way. Once a spring has reached its fatigue life there's no way to "rejuvenate" it.

When my starter went I put a rebuilt in. It's possible to replace just the Bendix mechanism but I figured the gear was probably buggered up also.

I didn't realize how slowly my old starter was cranking either. With the new one I have much faster cranking speed, which is critical in the winter.

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'81 300CD - 180K, cannot be killed by any conventional means
'99 Ford Escort - good MPG