The problem goes something like this (on a 1969 to 1985 diesel). Your engine normally starts just find when hot or when it has only sat for a few hours. But after sitting overnight, you find you have to crank and crank until the engine fires. It may even start and then quit once or twice. Once you get it running everything is fine.
Problem & Solution
Common among these chassis:
If this is the case it could be that fuel pressure in the injector lines is bleeding back to the fuel tank while the car sits for long periods. When that happens you have to crank the engine over quite a number of times until the pressure it built back up and fuel reaches the injectors.
There are a couple of one way check valves in the system that could be malfunctioning. The mechanical lift pump located at the bottom of the injection pump has a check valve that keeps the pump suction fuel. Also there is a check valve on the side of the injection pump (see picture) that keeps return fuel from leaking back down into the pump.
Recommendation: Before replacing the pump or the check valve Kent recommends you run two cans of diesel purge through your engine to clean out any gunk buildup. That could be the reason why the valves are not seating properly. If that does not help go after the check vavle on the side of the pump. Take it off and inspect. We only carry used ones when available (use search box). The last resort would be to replace the lift pump as these are expensive. From time to time we also have good used lift pumps