Gas fumes in the cabin when putting the landing gear down

[LKeener]

Gentlemen,
I'm noticing strong gas fumes while the landing gear is coming down. Anyone have any suggestions? I'm also getting fluctuations in fuel pressure at cruise settings as well as fluctuations in fuel burn during cruise settings. I'm looking for recommendations.
Best Regards,
Larry Keener
#15732

[9089P]

Hi Larry,

How old are your fuel bladders? Fuel smell on landing is a common complaint associated with leaking bladders. Apparently lowering the gear causes a pressurization in the wing which forces the fumes into the cabin. I would get on a creeper and look for "blue goo" on the bottom of the wing roots.

Good luck, Don

[N3322G]

Larry,

I'm no gentleman but ditto what Don said.

Suggest also being alert for fuel selector seepage between tanks as my selector went about the same time as the 40 year old bladders.

[LKeener]

Don & Pat,
Thanks for your response to my problem. I just replaced the left aux tank bladder three weeks ago, it was 44 years old. One main bladder is about 20 years old and the others have been replaced within the last eight years.
I spoke with Phillip at Webco today and he suggested pressurizing the line from the firewall forward to see if I had any leaks with the fittings and lines going to the carburetor. After that a host of other checks which will be done this weekend. If you think of anything else it would certainly be appreciated.
Best Regards,
Larry

[9089P]

Hi Larry,

I guess my only other thought is that if this smell developed in the last 3 weeks I would check all the connections for the left aux tank.

Don

[Andrew Foster]

We have a 61 250 with the 0-540. We have a JPI fuel flow 450. Fuel flow will fluctuate as the float bowl in the carb fills up, which equates to a flow between 14.5. - 16 GPH at cruise leaned to 50 rop at 75% or less power. The 0-540 only needs a min .5 psi for fuel pressure. At takeoff with WOT we see a very low fuel pressure on the stock gauge . I believe this is because you have a large volume of fuel, throttle plate wide open, thus low pressure as no restriction to flow, much like a garden hose with no nozzle . Once we reduce manifold pressure fuel pressure comes up and obviously fuel flow goes down.
We had the same smell like systems at gear extension. It was a bad bladder. I believe as the gear extends, the resultant fumes are transferred to the cabin with the increased airflow in the gear wells.
I agree about checking the connections on the newly installed aux tank.
Out of curiosity which tank manufacture did,you use for the aux?
Good luck and hope this helps

Andrew
7533P

[Don Keller]

Larry,
62 PA 24-250. My airplane did the same thing a couple years ago. It was minor seepage, not a leak, around the top of the fuel selector stem. Not only do you lower the gear when landing, but often switch to the fullest tank.

Good Luck, Don

[LKeener]

Andrew,
I replaced the left aux tank and bought it from Eagle fuel cells. I also had the shop replace all of the T connectors on each bladder.

[LKeener]

Don,
I'm pulling up the plastic fuel selector cover and looking at the fuel selector switch today. I'll see what that looks like and let you know.

[9089P]

Don has a very good point. I had an Archer that would give you a brief wiff of fuel every time you changed tanks. Wasn't worth the effort to take it apart to fix.

Don

[Kristin Winter]

Check the bolts that hold the tank to the filler plate. Those bolts should be torqued to about 25 in/lbs, or IMX, a shosh more. If they are loose, they will slop fuel to the top of the tank that then works its way down the wing.

[LKeener]

Thanks Kristin,
I will check that tomorrow after Church.

[George Kretschmann]

[LKeener]

I want to thank all of you that responded to suggestions regarding the fuel odor in the cabin. I found the problem day before yesterday. The fuel strainer gascolator was leaking all around the bowl but not enough where it was dripping on the ground. When I opened up the fuel strainer door I tried to put my hand around the bowl and it was wet with fuel. I ordered a new gasket and screen from Webco Aircraft and the problem is fixed.
Thanks again for all of your help.
Best Regards,
Larry Keener
#15732