Joe,
Assuming that your Vacuflush system is original, it should have a VG2 vacuum generator. The biggest maintenance issue on the system is the 1 1/2 inch duckbill valves. There are 4 valves per pump, 2 on each side of the pump that get clogged, dirty, or worn and will not seal well enough to build/hold vacuum as they should. However, there is an unlikely possibility that you have a perforated/leaking bellows. If you are going to replace the motor anyway even though that is not your vacuum issue, be sure to get the motor and bellows kit where you get the new bellows and motor for just the price of the motor, but be sure to install new duckbill valves or your system probably will not work.
Gerald