Piper PA-18 pilot reported an engine failure due to fuel starvation was the result of suspected malfunctioning fuel gauges that had indicated more fuel than actual was available.

Narrative

On Day 0; I had a total of three banner tows to complete. The day began with a ferry flight from ZZZ1 to ZZZ. The first tow was 2.5 hours long; from ZZZ2; to ZZZ3; and back to ZZZ. The second tow was programmed to be 3.0 hours; circling ZZZ4 and dropping the banner back at ZZZ. The final tow was supposed to be 1.0 hour. Before ferrying from ZZZ1 to ZZZ; I filled all four tanks (both outboard and inboard tanks) on the plane. The ferry flight took approximately an hour. I had enough fuel for the initial 2.5-hour tow; so I proceeded with the banner pick and completed the tow. After dropping the banner at ZZZ; I landed to refuel for the following two tows. At ZZZ; where there is no self-serving fueling; I asked the fuel crew to top off the tanks. While he was fueling; I went to the restroom and also gathered hooks for my next banner tow. However; by the time I returned to the plane; the fuel crew had left. Given the time constraints; I was unable to confirm with him how much fuel he added to the tanks. Upon checking the fuel gauges; they read full; so I assumed the tanks were indeed topped off. I proceeded with the banner pick; but halfway through that tow; I noticed that the gauges indicated about half a tank. This was unusual because if the tanks had been full; the gauges should not have dropped significantly. I considered two possibilities: either there was an issue with the tanks or the fuel crew had only filled the inboard tanks and not all four. At this point; I was 2 hours into the tow; with an hour remaining to return to ZZZ from ZZZ2. Given that the gauges showed half a tank on both; I believed there was sufficient fuel to complete the tow and return for refueling for the final tow and ferry of the day. As I was heading northbound at ZZZ4; the engine began to sputter aggressively. I checked all the gauges--fuel; oil pressure; oil temperature; tachometer--and they all read normal. Suddenly; the engine quit entirely. I immediately executed the engine failure checklist and pitched down for best glide. The engine restarted; which led me to suspect that there was ice in the carburetor; so I left the carb heat on for a while. Despite this; the engine continued to sputter and quit intermittently. Since I was towing over a beach; I began preparing for a water landing as per the engine failure procedure for banner towing. I was still on the frequency of 130.30 and announced on the radio that my engine was sputtering and that I might experience a complete failure soon. Other banner towers in the area were aware of my situation and informed me that ZZZ5 was nearby. Given that ZZZ4 is relatively narrow; I decided to turn westbound and attempt to reach ZZZ5. In the event of a complete engine failure; I planned to land on the water on the other side of the island; avoiding people; houses; or vehicles. At this point; I [requested priority handling]; and said my intentions to ATC. I continued to attempt the climb with full throttle but was unsuccessful. The engine quit multiple times as I was approaching the airport. About 4 miles from the airport; clear of any people or houses; I decided to deploy the banner to reduce weight and drag; hoping to gain enough altitude. After deploying the banner; I managed to climb to about 2;000 feet. I spotted the airport; glided down; and landed safely. After tying down the aircraft; I checked the fuel gauges; which still indicated half full on the right tank and about a quarter full on the left. However; upon inspecting the wings; I discovered they were completely empty. It became clear that the gauges were faulty and had given me inaccurate readings. I do; however; acknowledge that it was my mistake not to verify the fuel levels on the wings before taking off. Although I wasn't the one who refueled the aircraft; I should have been present to observe how much fuel was added. This experience taught me that regardless of time constraints; it is crucial to verify everything thoroughly andbe 100% confident that everything is good in the aircraft before starting a flight.