Good advice Rusty Wrench.

Valve clearance is part of a Tune-up, so that's part of the basic foundation. Always check those things.

The condensor is only used on points-based distributors, and there is no good way to test at home (?). You can swap a known good one or just try a new condensor -- they are supposed to be replaced every 12,000 miles anyways. The is another reason why we recommend going Electronic Ignition -- it is vastly more reliable. Many Datsun units are over 30 years old now and have never stopped working.