Fuel Smell in Cockpit

[Drew Shelley]

I have an M20E (1964).  Great plane!  It does have bladders.  Recently getting strong fuel odor with full tanks.  I removed rear seat and looked under there, saw a vent hose of some sort but can’t identify what it is.  The smell seems to be coming from that area.   Any ideas?  
 

I see no visible signs of external leakage.  Seems like a venting problem.  
 

Thanks for any ideas! 

[takair]

14 minutes ago, Drew Shelley said:

I have an M20E (1964).  Great plane!  It does have bladders.  Recently getting strong fuel odor with full tanks.  I removed rear seat and looked under there, saw a vent hose of some sort but can’t identify what it is.  The smell seems to be coming from that area.   Any ideas?  
 

I see no visible signs of external leakage.  Seems like a venting problem.  
 

Thanks for any ideas! 

Likely the water drain from the overhead duct. You should pull the interior panels. Very likely the sender or fuel hose is leaking into the cavity between the wing and the interior panel. A small amount of fuel there will leave a lingering stink. 

[Drew Shelley]

That is so helpful!  I will check it out. Will report back. 
 

[TTaylor]

Check your fuel selector valve as well.  The fuel smell is likely in the entire belly of the plane and will be difficult to find just from smell.  Look for the blue residue on and around fittings.  With bladders it is usually the fuel gauge senders in the the side walls or the fuel selector valve under the pilot. 

[Ragsf15e]

So you’re looking at probably removing both seats and the lower sidewall which is typically by the pilots left thigh.  Also the carpet around the fuel selector.  Probably gonna need to look at the bottom of the fuel selector as well.  Good luck!

[Nukemzzz]

On the E it’s by the front passenger hip on the other side of the lower wall. You might need new gaskets. A fuel boost pump or fuel lime leak smell can get into the cabin as well. My boost failed and leaked from the weep hole under the plane and I could smell that during stalls. You should assume it’s a dangerous leak if it just showed up. Gasoline is dangerous and we forget that sometimes. 

[carusoam]

Welcome aboard Drew!

First steps are to check the fuel floats as outlined above...

Next on the list is a small rubber hose connector in the fuel line in the same area... old hoses deteriorate...

If you are smelling fuel each time you open the cabin...

There is going to be traces of blue in the area...

Also check under the rug... fuel has a strong tendency to creep...

My M20C leaked at the fuel senders, and the hose/fuel line connector got brittle and cracked...

The rug turned blue, and the blue color crept up the side wall...  (before MS was around to ask...)

Old airplane smell is a cover story... it’s the smell of LL, and it doesn’t belong in the cabin...

 

Good news... low cost parts fixes like new...  

Best regards,

-a-

[Ragsf15e]

21 hours ago, Nukemzzz said:

On the E it’s by the front passenger hip on the other side of the lower wall. You might need new gaskets. A fuel boost pump or fuel lime leak smell can get into the cabin as well. My boost failed and leaked from the weep hole under the plane and I could smell that during stalls. You should assume it’s a dangerous leak if it just showed up. Gasoline is dangerous and we forget that sometimes. 

Well to be fair to both of us, it’s on both sides.  There are fuel tank senders entering the cockpit from both the left and right wing.

[Drew Shelley]

All,

Such good help!  Everything is opened up.  Pilot side sender unit gasket and that bit of hose.  Been leaking for awhile.  

Will let the mechanic make those repairs I guess.  I will put interior back together. 

Should I have them redo gasket and hose on other side?  

Thanks again!
 

 

[Ragsf15e]

Ahh, glad you found it.  It’s common.

There are some threads around here about fixing it.  I am not an expert, but I think I remember some folks talking about doing this repair pretty carefully/specifically.  It would pay to get some specific advice/plan before going in.  I think some people use a sealer on the gasket.  A litt google with “Mooney” in the search and you can find threads about leak at fuel sender.

Good luck!

[Nukemzzz]

On 4/17/2021 at 7:14 PM, Ragsf15e said:

Well to be fair to both of us, it’s on both sides.  There are fuel tank senders entering the cockpit from both the left and right wing.

Haha, I meant to say "Pilot and Passenger Hip"

[Derek]

Thought I'd throw in my recent fuel smell experience for posterity.

Never really noticed a smell during taxi, takeoff, climb out. One in cruise and leaning, would start to notice smell and it never cleared, just kept smelling for the duration of the flight.

I had an avionics project done (new panel, engine instruments and sensors, and Cies senders) not too long ago.

Initially though senders gasket leaking, but no blue, maybe gascolator, no blue. Never saw blue on the gear legs, wings, belly, anywhere I could see without unscrewing something.

Turns out it was the fuel pressure sensor fitting. (Opinion of the shop is that the avionics installer put an old fitting on the pressure sensor and never leak checked). Fuel was power washing the firewall... And right over the cabin air intake and exhaust.

Yikes!

I even had an oil change once in the meantime and the leak wasn't noticed by the shop that did the change.

Next time I smell fuel, I'm just going to land or go straight to the shop.

Edited November 12, 2022 by Derek

[A64Pilot]

On 4/17/2021 at 8:03 PM, Drew Shelley said:

 

Should I have them redo gasket and hose on other side?  

Thanks again!
 

 

I would especially if you have it all opened up already.

‘When were the bladders installed, how many years ago?