Your fuel pump runs from a push rod that rides on a lobe on the camshaft. The cam often wears as does the push rod. I have a 46 Ford that developed fuel pump problems. I tried a trick that an old timer told me about. I put a small piece of leather in the push rod cup on the pump. It lengthens the push rod and the leather doesn't seem to hurt anything. I used a common paper punch to punch a hole in a regular leather belt. The "punch out" is just the right size. My truck is original, including the 6 volt system and I do not want to alter it. I also didnt want to order a 6 volt pump. I only run the truck around my farm during the summer. Its not a perminant fix but the leather trick worked for me. Good luck.