Fuel gauge on ours hadn't worked in YEARS. With our gauge swapping etc, I decided there had to be a solution. Started down the troubleshooting path, eventually hooked up a temporary jumper ground wire between the tank sender and a known good ground and presto, gauge worked. Pulled the original ground wire out (went from tank sender up to a grounding spot on the engine) and investigated. A short section of the wire was swollen up. Cut into it there and found that section completely corroded. Replaced the wire and have been loving a working gauge ever since.
The corroded ground wire was the factory wire. It lives in the bilge on the hull bottom, so a potentially pretty moist environment. Any compromise in the wire insulation could allow water intrusion. Knowing the propensity for Malibu fuel gauges to not work, I wondered at the time how many others have the same issue with a potential of an iffy supply of original wire stock or a manufacturing process that may have damaged the wire during install.