After an engine has been assembled and installed, the oiling system needs to be primed before the intial start up. The assembly lube and oil used to lubricate the parts when the engine was assembled will provide some protection when the engine is first started. It may take 15 to 30 seconds for the engine to build oil pressure if the oil pump and oil galleries have not been primed.
On engines were a pan-mounted oil pump is driven by a distributor, a priming tool or a long screwdriver bit in an electric drill to spin the pump can be used to prime the engine. If the oil pump is mounted inside the front cover and is driven by the crankshaft, use a pressurized oil canister to feed oil into the oil system through the port for the oil pressure sending unit.