pudder

What are some of the common causes for a 1995 Mack CH to lose its fuel prime overnight? The truck has lots of hours on it (around 20,000+) and ever since the cold weather has hit, the truck will not start in the morning without priming the fuel pump. Could it be the primer unit, injector seals, return line grommets, or return line itself? Any common possible solutions to my problem would be greatly appreciated. Mike Anseeuw Brothers Ltd.