28- I'm trying to start a vehicle that has been sitting for a long time. What should I do?
This is a combined reply from a few threads (Run it or Not? That's the question, Starting a Bronco after being stored for prolonged period, & Engine has sat for 2 years). There's more info in those threads from several members that you might want to check out too.
You should expect the compression to be low at first after sitting several years with no oil on the rings. Dry rings alone will drop the compression. You should squirt oil in all 8 before trying to crank it.
My dad is a guy for bringing those back to life. He had a garage when I was a kid, then taught auto shop for years, & was always trying to revive some old engine. His routine was to change the crankcase oil & filter, squirt a little Marvel Mystery Oil thru the plug holes, rotate the engine without starting it just enough to coat the cylinder walls, add a little more thru the plug holes, & let sit for a bit before firing it up. He'd run the engine easy for little awhile (Maybe 15 minutes to 1/2 hour?), then change the oil & filter again. Of course the 1st fire up would smoke a lot as the oil burned out of the cylinders. Sometimes he'd mix in a little ATF (1/2 quart at the most) with the crankcase oil in the 1st oil change to aid in cleaning if he thought the old oil looked especially bad. He'd drive it easy for few days, & make the call after that as to whether or not it needed more work or just another oil change. It would usually work out pretty good.
And of course, check all rubber parts for signs of cracking or stiffness. Tires, hoses, belts, wiring, & especially anything handling fuel.
Look for signs of animal damage. Chewed wiring, nesting material under the hood, along the exhaust, or even in the intake to the air cleaner. I've actually removed nuts stored by squirrels from inside an air cleaner.
Check the brakes. Low fluid is not unusual after sitting for awhile. If the master cylinder is dry, you will probably have to bleed the brakes. Check the brake hoses for cracking, stiffness or swelling. Check the entire system for leaks after topping off the master cylinder & stepping on the brakes several times. Also step lightly on the brakes & hold them to see if the master cylinder creeps down. Even after inspection, be sure that they're working right before driving. Try them in the driveway several times before taking it out. Expect the brake drums & rotors to have some surface rust, but that's usually light enough to come off after a few stops. But the brakes might be prone to grab or pull until it's gone. Depending where & how long it was stored, the rust might be more serious. It's not a bad idea to check the condition of the pads & shoes anyway, you can see how much rust there is at that point. Does the parking brake work & release? Lube its cables while you're at it.
Check all the fluids. A radiator flush with a change of coolant is a good idea too.
There is also the condition of the fuel to be considered. Sometimes it has sat so long that the tank & components have a build up of varnish that requires removal, cleaning, or replacement. If you decide to not remove & replace/clean fuel system components, here's a routine for a carbureted engine
when the fuel isn't that bad. If marginally bad fuel is suspected, disconnect the fuel line at the carb & run a fuel hose from a small gas tank sitting on a blanket on the roof. I have used a lawnmower tank for years, & recently got a small boat tank for the job. So you have known good fuel & positive gravity feed to the carb for the first fire up. If there is a fuel issue at that point, you know the carb itself has the problem. Also remove & plug the fuel line before the fuel pump so you don't have to deal with it pumping bad gas just yet. Even so, still direct the output line from the pump safely into a container in case there's a little fuel in the pump. I like to run a hose to a can on the ground. Later the input to the pump can be reconnected, the line from the pump can be used to empty what you couldn't get out of the tank, & flush a little new gas through the system into the gas can while the engine is run from the temp tank. All of this requires attention to fire prevention (Being sure that nothing is going to pump, leak, or drip fuel anywhere & that anything spilled while making connections is wiped up, dried, & the rags removed from the area & allowed to dry before throwing or washing) since the engine will be run while some lines are disconnected.
If you are inexperienced or don't feel confident about taking on this type of work, seek advice from a local experienced person, or take it to a shop to do the work.