I have a 61 250 that always has fuel fumes in the cabin. The plane is kept in a closed hanger and is flown an average of 10 hours per month. There are never any stains on the floor or the wings. Typically the fumes are not as obvious while flying. We have replaced a 10 year old right main with out any effect (anybody need a good right main bladder cheap?). We have looked carefully at the selector at every annual and there never any stains. Do you have suggestions?

John,

Do you notice this more after filling the airplane, or is it just something that you notice after it has been closed up for a few days? Also, is there any difference in flight such as getting a wiff putting the gear down, or closing /opening the vents? Are you by chance fuel injected? If so you may have a seep from the electric fuel pump under the copilots floorboard. If you have a stock fuel pressure gauge, check the line that runs to it as well as the gauge. Fuel leaks are easy to find. Seeps, not so much, as they smell worse than they appear most times. Look for blue or BROWN staining around any fuel fitting, valve, or pretty much anywhere any raw fuel is present. Pull the wing root fairing strips from the bottom of the wings and check for stains as well as the security of the hose clamp on the tank nipple. Verify the tank bolts are properly torqued and that the scupper drain line is hooked up and the fuel filler caps are properly fitting. One other place many folks miss is a seeping fuel strainer valve. This can be missed as it gets "cleaned" off evey time you drain fuel, but it can fill the cabin with enough fumes that it is noticeable after it has been closed up for a few days. These are hard things to sort out from a distance, but maybe there is something in here that might point you in the right/different direction from where you have been looking.

-Zach

Thanks I will investigate and report

You might want to check the fuel selector as well. We have had a slight fuel smell in the cabin that persisted after all the cells were replaced. Fuel strainer was rebuilt but no change and fuel pump rebuilt as well. We opened up the area around the fuel selector so we could remove and rebuild it as it's operation was sticky. There was an obvious fuel leak I suspect was coming from the fuel selector. Not reinstalled but let you know if this cures the problem.

Don