You can check the pressure of the system with a gauge. Also you can buy R134 with a green dye mixed in it and charge the system yourself. Some cans of R134 come with a gauge on the can. Some other things to note. When you say the compressor catches, you mean the belt spins for a second and shuts off. If there is still pressure in the system, check the pressostat switch. It's mounted on the receiver/dryer and has two wires coming out of it. If it has worn out, it will tell the compressor clutch to disengage thinking that there's no refrigerant in the system. I think some people hot wire it with a paper clip but I have no idea what that does to a compressor.Try it after the evac and refill session. Sometimes it's just the compressor clutch. I got a compressor rebuilt in China on ebay for $120. It still works two years later but who knows how much longer