We were supposed to start our trip today, but yesterday while enroute to New Jersey to get the large capacity fuel tank installed I climbed up to 19000 feet, established in cruise and the engine started coughing up. With low clouds down below, I immediately started looking for a break in the clouds for a possible emergency landing. At the same time, I switched the fuel tanks but the engine roughness did not go away. I pushed the fuel mixture to full rich, still no change. Next, turned on the fuel boost pump, the engine stopped coughing. Let it run for a minute or so and then turned the boost pump off and the engine roughness returned. So, now I know something is up with the engine driven fuel pump. With another 500 nautical miles to go to get to New Jersey, I decided to abort and return to the airport where I could find a mechanic. I contacted the air traffic controllers and informed them of my problem. They asked me if I wanted to declare an emergency, but since engine was still making power, I decided to hold off on declaring the emergency. I started my descending turn towards Greenwood Indiana. My plan was to remain as high as I could, just in case the engine quits, and then dive and land. I established a shallow descent and marked a point about 7 miles from the runway threshold as the point to make the in bound turn towards Greenwood. Fortunately, weather was clear at Greenwood so I did not have to shoot an instrument approach. Levelled out at 7000 feet and once lined up with the runway I dived at about 2000 foot per minute to an uneventful landing.
Once on mother earth, I contacted the engine overhauler to discuss the situation with him. He advised me that due to less dense air at altitude the engine driven fuel pump heats up and starts vaporizing fuel before it can get to the engine. He advised me to get airborne again and when I encounter the engine roughness again, to enriched the fuel air mixture and use the fuel to cool down the pump. Since this engine has only about 130 hours on it, everything else is running fine. I decided to have my mechanic make some minor low idle mixture adjustments and after filing an instrument flight plan, departed again for New Jersey.
At 17000 feet the engine roughness returned. I enriched the fuel mixture, no change – the roughness did not go away, but the engine temperatures started rising. Well, that was not as advertised ! I requested the air traffic controllers to give me 15000 feet as my final altitude as the engine was running fine there. After establishing the plane in cruise, I kept a very sharp eye on breaks in the clouds and distance to the nearest airport, just in case…..
Arrived in New Jersey and got the Air Mods people busy installing the fuel tank and all its modifications. In the meantime, I opened up the engine cowling and started inspecting the air flow around and to the engine driven fuel pump. There seemed to be several small obstructions, by design, which would not allow free flow of air to the fuel pump. The turbo normalizer generates about 1400 degrees C at the inlet and that heat has to be dissipated as well. The reduced density of air at high altitude means there are less air molecules to cool the pump down, therefore there needs to be some ram air coming in from the air intake in the front of the engine to keep things cool. I then discussed this with a few mechanics and they all seemed to agree with my findings….so far so good.
After the fuel tank was installed, the weather had been progressively turning bad in Southern New Jersey. I filed my flight plan and during the takeoff roll, found about 15 Canadian Geese sitting on the runway. I had to abort take off and chase them off the runway with my lights and sound of the engine. Came back and took off. Since the problems with the fuel pump occur at altitudes above about 15000 feet, I decided to stay low for the entire return trip and maintained 6000 feet all the way back to Indiana.
The plan is now to discuss my solution with the engine builder and test fly the plane with my recommended modification to see if this will alleviate the problem. If it does not fix it, then I am going to fly to Tulsa, Oklahoma and take the plane to the engine builder to figure it out before I decide to launch across Atlantic, Indian and Pacific Oceans….. this is a major set back, but we must fix this before we launch….