Damaged to stored car
 

What kind of damage can be done to a car that sits for 3 years in a garage?

Dry rotted belts hoses tires the engine could be locked up doutful that's happend but it can the seals in the engine can be dry rotted lot of things if it wasnt started every now and then

Mice love to chew on wiring harnesses

tires can flat spot

mildew can grow

..... the list can go on and on, but it depends on the climate that it was stored in and how it was stored... did the person take the proper steps when they stored it 3 years ago to prevent issues or not...

did it sit and never run? or move?

I snapped the alternator belt so it has not been started. but I do move it.

The fuel has probably separated and varnished. Needs to flush the gas tank and fuel lines. If it's carbed...dump the fuel bowl, Gumout everything! Injected? Powerflush.

The rings might have corroded to the cylinder walls. Remove the spark plugs and spray a good penetrating oil generously into each cylinder. Let it soak in real well then crank the engine over with the plugs out. Change the oil immediately. In fact, replace all of the fluids now!

Be careful... stinging insects like to nest in abandoned air cleaners, head liners and trunks.

The battery is quite likely junk. You could try to charge it and get it tested. Clean the battery connections. Make sure all of your accessories spin. Corrosion can attack the bearings in your alternator, PS pump, AC compressor, etc. The brushes in the alternator might bind.

Brake fluid is hygroscopic (sucks up moisture). Flush your brake hydraulics before you drive the car.

general aging and dry rotting of and rubber parts, fuel tano and lines would get H2O in them, top of the engine block could be dry, carb could be dry, tires flat, battery dry, etc

Yup I can attest to the wiring harness being a favorite meal. Been there had to replace that.

also be sure to check the air intake. I found a mouse nest in my stored car at the beginning of last summer. It was past the filter too, and the filter didn't have a hole chewed in it. . . Still trying to figure out how the hell it got in there.