I eventually switched to a much heavier fuse holder and soldered the wires to my relay terminals. Replacing the fuse won't fix it. I never had a voltage problem after that. Years later,when I removed the pump to upgrade to a double pump set-up,I noticed the power wire had a pretty good kink just before the pump connection. After finding that,I suspected that the kink was the actual cause of the resistance because there was very noticeable sings of heat at the kink. After you find and fix connection problems,re-connect the hotwire and check voltage. The goal is to get more voltage to the pump,so you must run the hotwire and a volt booster is a must because the pump will receive even more voltage. You have a voltage problem,but also have another problem with the wideband that will have to be addressed.