On December 21, 2020, at 1525 Pacific standard time, a Navion A, N4106K, was substantially damaged when it was involved in an accident near Livermore, California. The pilot was not injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight. The airplane had new wingtip fuel tanks installed in July 2020, and an annual inspection was completed at the same time. The accident flight was the first flight since the fuel tank installation. The pilot departed from runway 7R at Livermore Municipal Airport (LVK), after a normal runup inspection. The engine developed full power during takeoff; however, at an altitude of approximately 500 ft above ground level (agl), as the pilot turned onto the crosswind leg of the traffic pattern, the engine began to surge and lose power. As the pilot reduced the power for landing on the downwind leg, the engine lost total power. When the pilot realized the airplane would not make it to the runway, he prepared for a landing on the grass area parallel to the runway. The airplane touched down and the left wing impacted concrete blocks. A postaccident examination of the engine revealed a leaking gascolator fuel inlet line and a loose hose clamp connection on the fuel line from the fuel selector to the gascolator. The line was made of rubber instead of aluminum tubing, and the fuel selector's connection was improper. Additionally, the wingtip fuel tank installation revealed several inconsistencies with the installation, such as loose clamps and improper hardware installed.