Before initial start up of a rebuilt engine, which step should be performed?

• A. Release the parking brakes
• B. Prime the lubrication system
• C. Compression test
• D. Cylinder leakage test

Answer: (B)

Priming the lubrication system is the crucial step before the first start because after a rebuild the oil pump and passages can be empty or filled with air. By priming, you fill the pump and all oil galleries so oil pressure builds quickly as soon as the engine turns, protecting bearings, cams, and other moving parts from dry start wear. Without priming, the engine can start with little or no oil pressure, leading to accelerated wear or damage on the initial rotation. The other options don’t prepare the engine’s lubrication pathway for start-up, and while compression or leakage tests are diagnostic checks, they’re not preventive steps for the very first start.