Dealing with a car that has been sitting for a while can be a daunting task. The story is always the same- " The car ran fine until it was parked and sat for X years ". You have an old car that reportedly is in good mechanical shape, but doesn't run simply because it has sat too long. Where to start and begin depends on a lot of variables, like exactly how long it sat parked, where it was parked, and the climate. Some times you don't even have the benefit of knowing these factors and your safe bet is to start from the ground up and rebuild.
The steps I am going to be taking on my Thunderbird are the bare minimum needed to give that old engine a fighting chance at being a second chance, with out a complete rebuild. I've come across these tips and trick over the years from other gear heads, forums, and blogs like this. It is hardly an inclusive list and is not perfect for every situation, but these steps should benefit any vehicle that has sat for a long period of time. I would go ahead and buy the cheapest parts you can for replacements. No sense spending cash on the high end stuff only too find out there is a lot more work that needs to be done than some new wires.
FLUIDS AND FILTERS
1. Drain and replace the gas. Gas can go bad, over time it degrades and is not as combustible and the car will not run well. Given enough time it will oxidize and there will be a varnish film that can gum everything up. I would take the time to pump it out or drain it and fill her up with a fresh tank of gas. I like to use SeaFoam time time anyway, and this would be a great time to add it to the tank to help clean up and deposits left from the gas oxidizing. This guys seems to know a lot on the subject
2. Replace the fuel filter. Nobody seems to replace the fuel filter, and I don't know why. It is cheap and easy, and with your gas take empty it is the perfect time to get a new one in there.
3. Drain and replace the oil. It is undoubtedly gunked up and nasty by now. It was probably due for an oil chance 1000 miles before it sat untouched for all those years anyway. Once it is drained ad a quart or so of marvel mystery oil in to the crankcase to help clean it out. You will be replacing the oil again very shortly so go ahead and buy the cheap stuff.
4. Replace the Oil Filter. Goes without saying really. Why would you ever change the oil without the filter too? You wouldn't and shouldn't. They only cost like $5 stop being cheap.
5. Drain and replace the coolant. I don't actually know if coolant can go bad, but it is easy enough to do. While your at it take a peak at the thermostat and replace it too.
IGNITION SYSTEM
6. The battery is likely toast. Most all auto parts stores can test and charge your battery - so it is worth a shot. I got luck any the Interstate Battery was still under warranty for the Thunderbird. But you should be prepared to just buy a new one.
7. Cap and Rotor replacement. Chances are really good that Cap has dried up and cracked. Give it a good once over and replace it there is any doubt.
8. Spark plug wires. These guys might be corroded and dried up. If they feel stiff and hard to bend get new ones.
9. Replace the spark plugs. Probably not necessary as they don't go bad sitting, but you've replaced everything else so why not. Plus you have to take them out for the next step.
MECHANICAL
10. Pull the spark plugs and squirt a healthy helping of marvel mystery oil in each cylinder. I used 1/8 quart per cylinder and let that sit over night to work its way into those rings.
11. Place a towel over the heads and turn the engine over by hand using a breaker bar at the crank pulley. This is just to make sure it is not seized up and moving freely.
12. Now you can turn the car over a 2-3 times for no longer than 10 seconds ( to avoid burning up the starter) this will expel the extra oil and prime the oil.
( some people recommended taking off the valve covers and taking out the dist to prime the oil with a drill - and check to see the oil comes up and is flowing. Not a bad idea at all )
13. Put the new properly gapped spark plugs in and make sure everything is hooked up.
14. Spray a decent amount of starting fluid into the carb and stand back. Now you can try to start the motor. It is helpful if you have a remote starting trigger and a fire extinguisher handy, but with any luck the engine will come to life.
15. Let the engine idle for a bit and make sure to watch the temperature. If you don't have or can't trust the gauge, a laser thermometer pointed at the thermostat housing works well.
16. Tune it up - Article coming soon. Check the timing and idle speed..
17. Coming Soon - Don't Drive it yet, Few more things to check before it is road worthy.