I have a 78 E-150, 351, 2bbl, 110K original miles. It acts like the fuel pump loses its prime after sitting 3 or 4 days. It is very hard to start to the point of nearly running the battery down. I just replaced the fuel pump about a year ago and there are no visible or smellable leaks. Thanks for any help that anyone can give.

 

Run rich at all when it finally starts? Visable fuel smoke after a start? Or just over extended cranking times?

One possibility,, the carb float bowl would/should be full (or close to) even after sitting for a 'reasonable'time, and even if the fuel pump lost prime and/or emptied the line it should still fire off with the fuel contained in the carb bowl.. Sometime the power valve on the bottom of the bowl (cover on underside of the carb) will leak and bleed through with an aged cracked diaphram andall the fuel in the bowl drains into the intake.. Then on a restart (usually over night ect) the engine may be flooded with raw fuel, but usually will start with some moderate cranking time and more often than not, some fuel smoke until the extra fuel is cleared.. Given it's vintage, something I'd consider, as would a good hot spark (or the presence of) during a cold crank situation..