Reener
07-14-2009, 12:31 AM
Sunday I began what was to be a week of intensive IFR training. The morning engine start and run-up at KFHU were typical and uneventful. After flying to Tucson and shooting approaches at Tucson International and then Ryan Airfield, we made a full stop landing to eat lunch. During the 2.0 hours of flying time, the engine ran smoothly and without problems. One hour after shutting down for lunch, with the outside air temperature at 111-113, I made a succesful hot start, but could not get the engine to run smoothly, with or without boost pump on low, and regardless of mixture setting. Engine RPM was all over the place and I kept having to run 1700-2100 RPM to keep it from dying. I taxied out to the run-up area, and it got worse. During mag check, I got 300-400 RPM drops on right and left mags. So, I taxied back to the transient parking area and called it a day. There being no available mechanics on the field on Sunday afternoon, I had to call my son and my wife to transport my instructor and me back to Sierra Vista. Monday morning I called a mechanic at Ryan Field and he agreed to look at the plane. We drove back to Tucson, and I started the (now cold) engine with him in the right seat. All was normal. He thought we'd experienced severe vapor lock from the heat. I shut the engine off and we went to the pilot's lounge to plan the day's flight. We then topped off the tanks with 10 gal. each of cold from the ground fuel. About 30 minutes after shutiing down, I made another successful hot start, and the RPM seemed fairly stable. As I taxied out, it once again began to vacillate, just like the day before, so I turned around and went back to the ramp. At the ramp, I shut down and again called the mechanic. This time he towed the plane to his hangar and removed the cowling to investigate. The bottom spark plugs were incredibly fouled with both little pieces of lead and carbon deposits. They're about 200 hrs. old. They are being replaced. The fuel injectors are also going to be cleaned and the mags both thoroughly checked.
Up until now, the engine has been perfect in 350 hours of operation, using essentially no oil between oil changes. The disparity between the normalcy of operation after a cold start and the unflyable engine behavior after a hot start was striking. Has anyone had a similar experience? Do any other desert dwellers make hot starts in those kinds of temperatures and run smoothly?
Up until now, the engine has been perfect in 350 hours of operation, using essentially no oil between oil changes. The disparity between the normalcy of operation after a cold start and the unflyable engine behavior after a hot start was striking. Has anyone had a similar experience? Do any other desert dwellers make hot starts in those kinds of temperatures and run smoothly?