On February 20, 2022, about 1115 central daylight time, a Ryan L-17B airplane, N5042K, was substantially damaged when it was involved in an accident near Livingston, Illinois. The pilot receiving instruction, the flight instructor, and the passenger were not injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 instructional flight. The pilot receiving instruction reported that the purpose of the flight was to practice various flight maneuvers. The airplane departed about 0943, and the training was successfully performed. About halfway back to the departure airport, the pilot noticed that the engine was “running rough.” The pilot proceeded to lean the airplane’s fuel mixture to correct the problem, and he then noticed that the fuel flow gauge was “pegged.” The pilot continued to lean the mixture and adjusted the throttle, but the airplane did not respond to these inputs. The airplane began to lose altitude, and the pilot receiving instruction performed a forced landing to a flat muddy field. During the landing rollout, the nosewheel turned left in the mud, the airplane spun around, both wings and the propeller impacted the ground, and the airplane came to rest upright. The airplane sustained substantial damage to both wings. The flight instructor, who was also a mechanic, reported that, when the engine was running roughly, he tried to lean the mixture with no engine response. He also reported that the fuel flow gauge needle had advanced into the manifold pressure side of the gauge and that the throttle had no response. The flight instructor assumed that the fuel control unit had a mechanical issue. Postaccident examination of the airplane found no mechanical anomalies with the airframe and engine. Fuel injection system testing was conducted. During the fuel pump testing, the fuel pressure was 4.5 pounds per square inch (psi); the standard is between 9 and 11 psi. The fuel control valve was found leaking through the screw to the metering insert. The fuel flow level would not stay set during the testing. The fuel control valve was disassembled, and the shafts and metering valve were found to have internal damage. The manifold valve was found leaking fuel to the air side of the diaphragm. The interior of the fuel pump had a dark deposit. The fuel pump was provided to the NTSB’s Materials Laboratory, which found that the deposit was firmly adhered to the surface and could not be removed. The deposit was viewed under magnification and found to be consistent with corrosion/oxidation of the surface material. Continental Motors released Service Bulletin SB-04A, Fuel Injection System Contamination (issued in March 2008 and revised in July 2016). This document provided guidance for maintenance personnel to prevent contamination of fuel injection systems during installation and maintenance work. This document states in part the following: o All caution must be exercised during reassembly of the fuel system to NOT allow any contaminants to enter the components, lines and fittings during installation. o All surfaces surrounding the area where components are to be installed must be clean and free of all forms of contaminant before and during installation. o All hose assemblies must be flushed and verified to be free of contamination prior to installation. o All fuel system component and lines must be capped and remain capped until flushed and ready for installation. o The engine, tools and environment must be clean to minimize any potential for fuel system contamination. o All fuel system components, regardless of their source, must be purged at time of installation. SB-04A concluded with a warning that stated, “Fuel system contamination may lead to fuel system component damage, erratic engine operation, loss of power, or engine shutdown.” A review of maintenance records showed that the engine and its fuel system were overhauled in November 2017 and that the engine was installed in the accident airplane that same month. The maintenance records showed no further work for the engine fuel system. The maintenance records also did not indicate compliance with Continental Motors Service Bulletin SB-04A during the overhaul work performed in November 2017. The Federal Aviation Administration does not mandate compliance with service bulletins for 14 CFR Part 91 operations.