Skyhawk 172/Cutlass 172
Flight Crew Private
Flight Crew Last 90 Days 20; Flight Crew Total 270; Flight Crew Type 240
Distraction; Confusion; Troubleshooting
Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural Published Material / Policy
Aircraft Equipment Problem Dissipated; Flight Crew Landed As Precaution; Flight Crew Overcame Equipment Problem; Flight Crew Inflight Shutdown
Aircraft; Procedure; Chart Or Publication
I did not follow the placard instructions to switch to single tank operation above 5;000 feet; installed on my C172G per AD 72-07-02. The aircraft was full of warm fuel from a desert airport and had been out in the sun. We were cruising lean at 8;500 feet indicating 105 or so MPH. We were 8;000 AGL or so. The engine slowly lost power; sagging and partway recovering on a 10 second period; before losing all power. Carb heat (sustained); mags; mixture (both ways) had no positive effect. We were well within range of MIT and headed there. We switched tanks around rapidly; to no effect. We then stuck on right tank for a while; and later switched to left; and the engine then regained power around 6;000 MSL. Subsequently the engine ran on either tank. We landed anyway. All engine sumps were OK; etc. and we determined that the problem was not following the placard. We then flew home 2.5 hours.What seems odd to me is that we unknowingly restarted the engine using a procedure found in the 1964 POH; but not in the 1966 POH. It would have been helpful if the procedure appeared in the 1966 POH that I have for my plane. People flying this plane above high ground really should know about this procedure. There are rumors out there that this placard is nonsense that 'got the FAA off Cessna's back' about some unexplained engine failures; which is misleading.
A C172G/U with tanks full of warm fuel lost power because of a vapor lock at 8;500 feet but was able to regain power by switching fuel tanks as per a 1964 POH procedure which is not published in some later POHs.