Fresh Water Pump-But No Water

I have a 2008 Keystone Copper Canyon Sprinter. I thought I had a fresh water pump problem so I installed a new Shurflo 4008 pump. Opened faucets, but no water. All connections in trailer are tight and I don't believe I have a vacuum leak. Pump has suction and pressure. I disconnected the line to the fresh water tank and blew it out with my compressor. Water came pouring out of the line. I reconnected it and pump worked for a minute then quit pumping water. My question is: is there a check valve between the fresh water tank and pump that could have gone bad, or is there something else that could be wrong with that line? I have not yet taken off undercarriage cover to check line.