Dual fuel tank problem

[Thunder7869]

I have just purchased a 1974 wellcraft v20 with dual fuel tanks ( one port one starboard) and last week we were out and had an issue trying to get fuel from the port tank to the engine! ended up having to call US boat tow for gas. We had 3/4 of a tank on the port side, ran the Stbd side empty. no matter how long we pumped the fuel bulb, we got zero fuel from the port tank.... any suggestions?