Does the 1983 Chevy silverado Crew Cab 6.2 Diesel use a mechanical fuel injection?

No, the 1983 Chevy Silverado did not offer a crew cab body style. The crew cab configuration wasn't introduced until later. Therefore, there's no 1983 Chevy Silverado Crew Cab with a 6.2L diesel, mechanical or otherwise. The 6.2L diesel was available in other body styles that year, but it used a mechanical fuel injection system.