The Ranger has a reasonably good reliability record, although injector failure is a known issue so look for excessive smoke under acceleration. It's not a major repair, though, as most decent garages would be able to do the job without it being too expensive. The only other real issue we've seen reported is a few engines where the oil pump has failed destroying the engine. It's rare, but we'd steer clear of anything with an incomplete service history for this reason, as dirty oil is the most common cause of pump failure.