Earlier today my truck stalled, I discovered that there was no gas getting to the carb. Took apart the fuel pump and found that one of the check valve diaphragms was unseated. Put it back together and it ran. Took off again and now and hour later I'm on the side of the road. Took it apart again, check valve is in place, put it back together and nothin. Any ideas? I'm stuck here with nothin but a screwdriver! (235 engine, 61 C10)