Bonanza 35
Flight Crew Air Transport Pilot (ATP); Flight Crew Multiengine; Flight Crew Instrument; Flight Crew Flight Instructor
Flight Crew Last 90 Days 5; Flight Crew Total 5300; Flight Crew Type 120
Aircraft Equipment Problem Critical
Flight Crew Returned To Departure Airport
Aircraft
I departed from Runway XX at ZZZ. At the departure end of the runway; the aircraft backfired and power fluctuated. I was able to return and land at ZZZ. Prior to flight; I had sump-checked each fuel tank and the fuel selector valve; at the low point. All fuel samples were found to be clean; with no contamination. The engine run-up was normal. I departed with 70.1 gallons of usable fuel. The engine ran smoothly while utilizing the electric auxiliary fuel pump. Subsequently; the JPI930 Engine Monitor's memory indicated a fuel delivery issue at the time of fluctuation. I checked all fuel lines and found them to be clear and free flowing. I then sent the suspected failed engine-driven fuel pump out for assessment and overhaul.
A Bonanza 35 Pilot reported engine power loss on initial departure climb and later identified an issue with the fuel pump.