It could be a few things....
1. A pressure switch could be bad.
2. Did you ever add freon with compressor oil? A system will also lose oil along with the freon. The compressor could be locked up.
3. If the leak is on the suction side it will draw moisture into the system and possible affect the...
Hello & welcome to the forum.
This might get you started.
http://www.tractordata.com/industrial-tractors/000/1/7/177-ford-4400.html
Nice tractor, boy I could have used something like that on my place a few years ago.
Good luck!
Here is a link to a parts supplier, you will be able to see what all you need and it's a starting point to figuring out what aftermarket stuff will work if you wish to go that way.
http://www.messicks.com/newhollandparts.aspx
Good luck!
Dis you make note of it's timing position when you took it out?
From what I have seen, there is timing marks on the flywheel. And it should be somewhere around 4 degrees before top dead center.