Recommissioning a Long-Parked Classic: How to Safely Wake a Sleeping EngineYou finally got the barn find home. The temptation to drop in a battery, splash in some fuel, and crank it over is almost irresistible. Resist it. An engine that has sat for years is full of dried-out seals, varnished fuel, and dry cylinder walls, and a careless first start can turn a running engine into an expensive paperweight in seconds. Recommissioning is about patience. Done right, it gives an old engine the best possible chance of running reliably for years to come.Begin with a thorough assessment before any attempt to start. Drain the old fuel completely, because gasoline that has sat for years turns into a varnish-like sludge that will clog every passage in the fuel system. Inspect the fuel tank for rust and debris. Check all the fluids, looking for milky oil or contaminated coolant that could indicate deeper problems. Examine belts and hoses, which will likely be hardened and cracked, and inspect the wiring for the rodent damage that is almost universal in stored cars.Next, make sure the engine actually turns freely before you ask it to run. Remove the spark plugs and squirt a small amount of penetrating oil or a marine fogging oil into each cylinder, then let it sit for a day or two. With the plugs out, gently try to rotate the engine by hand using a breaker bar on the crankshaft bolt. If it turns smoothly, you are in good shape. If it is locked solid, stop and address the seizure properly rather than forcing it, since a stuck engine forced to turn can bend rods or crack rings.AdvertisementAdvertisementPrime the system before the first start. With the plugs still out, you want to build oil pressure so the bearings are not running dry on startup. Many enthusiasts pre-lube by priming the oil pump or simply cranking the engine on the starter with the plugs removed until the oil pressure gauge shows movement. Replace the spark plugs, install fresh fuel in a clean system, fit a new battery, and double-check that you have coolant and a functioning cooling system before it runs for more than a few seconds.When you do start it, keep the first run short and watch everything closely. Listen for knocking, watch the oil pressure, and check for leaks and overheating. Do not rev it. Let it warm up gently, then shut it down and inspect again. Plan to change the oil and filter almost immediately after the first successful run, because that initial startup will dislodge years of accumulated gunk. Replace the brake fluid, coolant, and other fluids as part of a complete recommissioning. Take it slow, fix problems as they appear, and you will transform a dusty relic into a dependable classic you can actually enjoy driving.Related reading1969 Camaro SS Revival After 22 Years in StorageHow to Value a Barn Find Car