I had an O-200 equipped Coupe and had the transfer pump fail in a pretty dangerous way. The pump operated right up to, and during the failure. I had a partial engine failure over the mountains in Northern California. The engine started losing power quite smoothly just as if the throttle had been pulled. I immediately went full rich and full throttle and the engine picked up.
Since the engine was running smoothly and I had plenty of altitude I went back to Red Bluff and landed. Inspection found nothing amiss so the next day I decided to circle the airport and gain all the altitude I could and then fly on home. At about 7-8000 feet or so the engine again lost power so I landed and trailered the plane home. Upon taking the carb apart I found the bowl nearly filled with flour fine metallic particles. The Marvel carb has a well where the mixture valve sits and this had filled up and leaned the mixture. As soon as I touched the mixture control I disturbed the stuff enough to get some fuel flow back. I traced this to the fuel transfer pump. it had been hammering itself to pieces while still working. It ground pieces so fine that they passed the rather coarse screen on the header tank and the finer screens at the carb and gascolator. This formed kind of a metallic paste which settled in the carb bowl. I had the carb apart maybe 50 hours before the failure and found no foreign substance. It looked like internal corrosion had started the failure mode. Repair consisted of replacing the pump, Repairing the carb and spending hours siphoning fuel from the header tank, filtering it returning is and repeating the process until I got no more metal flakes on my filter paper. I used a flexible plastic tube on the siphon ti reach all corners of the tank. By the way the removable screen on the bottom of the transfer pump alway had shown clean upon inspection. Because of my own experience, I really look carefully at any of those "clicker" type fuel pumps when I do an inspection. Cheers: Paul N1431A KPLU
