Fuel in the header decreasing with fuel in mains

Way to go Steve! ...........and thanks for letting us know what it was.

I am happy to report that the problem is solved thanks to Marvin Dunlap, EOC Tech Support Guru. Before I finished explaining the problem Marvin had the answer. I had an air leak in the fuel pump cover that we take off at each annual. A new cork gasket and fiber washer did the trick.

Thank you Ben for the ideas. I am working on the airplane now and will be ready to experiment with the fuel system this weekend. The wing tanks are dry and the header tank will be down to the indicator at the bottom of the gage. I will put three gallons in each wing tank and see if it transfers to the header. That should determine if the pump is working with the wing tanks low. I have disconnected the fuel lines in the fuseloge and blown them out, all seem clear.

Hi Steve,
First let me say that I am no expert here but have had previous problems concerning fuel in the two coupes that I have owned.
My first coupe experienced the cork float in the head tank becoming "gas logged" due to the cork coating becoming compromised from possible alcohol in the fuel and sinking rapidly but with the tank full of fuel. We ended up installing a metal float to ensure that the problem never occurred again. I assume that your tank was indeed low when you say your float indicated low fuel in the head tank (?). My other experience was with my current coupe. When I bought it, it hadn't flown for about 3 yrs and the fuel pump would not pump fast enough to keep the head tank full. We rebuilt the fuel pump we believe that the check valves were sticking or leaking. We replaced both valves and the diaphragm. I'm betting your problem is with the pump again, especially after you relating your story of the float disintegrating and particles floating around. I know you said that things were cleaned good but it wouldn't take a very large particle that might have been overlooked to get stuck in one of the pumps check valves and causing problems. Please let us know what you find........

On a recent trip from Texas to Tennessee the fuel in the header tank started decreasing after 2 .5 hours of flight. The first time I was close to the leg destination and landed with fuel still indicating on the sight gage. On the final leg of the trip at 2.5 hours the fuel gage started down rapidly ( I understand that the shape of the tank causes the indicator to go down more rapidly). Both times it happened at the 2.5 hour point and both times I still had fuel in the wing tanks, the wing quantity gage was very close to the bottom but still bobbing some. On that second leg I landed 20 miles short of destination because the header gage was at the bottom of the indicator (trust cork indicators). During the next legs after refueling the fuel system operated as designed both times. Has anyone had a symilar problem?

I have had previous fuel problems. The previous owner installed a plastic bobber, purchased from Aircraft Spruce, in the header tank The bobber was a Model T ford part and apperently not suitable for aviation fuel. The bobber disintegrated leaving small pieces of plastic in the header tank that found there way to the carb. After a failed fuel pump overhaul, carb overhaul and a header tank cleaning, I thought the problem was solved. This may have nothing to do with the current problem but it needs to be concidered.

Steve Freeman