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180 Fuel Odor

18180

18180

Registered User
Pennsylvania
Every now and then when I open up the door on my 180 I am greeted with a pretty strong fuel odor. I have inspected every line , the valve and the vent line connecting the tanks. No staining, no leaking, nothing. All I can come up with is possibly vapors in wing making their way into the cabin through the wing roots. Theories welcome.
 
I will. Been under the panel a lot for recent xponder install so nothing obvious.


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Look really closely at the nipples on the fuel bladders for the vent crossover. They tend to dry out and crack. It can be really hard to see the cracks, so use a bright light, and maybe a magnifier.
 
Can't recall where aileron cables and fuel lines run in 180, but in a 206 I flew, I started smelling gas a little. Took fwd door post trim off and found that the aileron cable was looped over the fuel line, and had sawed through the line....barely.

Scared me even now, thinking about that one.

MTV
 
Cable-fuel line shared space looks like this. Gotta undress the door post to inspect.
 

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Not sure if they're the same as MTV's 206, but I had a fuel line perforation on a 185. The plastic door post trim that holds the map light switch forward of the left door got cracked. That allowed one of the sharp map switch connectors or mounting screws (?) to contact the fuel line between it and the aircraft exterior. Flying to Fairbanks on floats I noted a thin layer clear fluid on the floor under my hip boots, thought it was just water from repeated landings and takeoffs. No odor of fuel so kept trucking.

Landed and pulled to the float pond bank and then smelled the fuel. By then maybe 1/4 inch of fuel covered the pilot's foot well so unazzed the ship without touching the electricals. Mechanic soon came to yet unburned plane and pulled away the cracked panel. A small stream of fuel sprayed out so he took his leatherman pliers and crimped the fuel line above the leak.

The perforating whatever must have not been powered up because a spark would have done the deed.

GAP
 
Many years ago I discovered a cable just making contact with the fuel line in the rear door post----a little above the door latch so I bent the line a little and problem solved. My 54 doesn't have that big blue fitting in that spot.
 
I have had the door posts open and have found and replaced fuel line in a couple of spots. I am quite confident it is not a fluid leak in any line or fitting though i have not capped the ends and done a pressure/vacuum test....yet. Also noted some staining on fuel valve so that has been resealed and is now dry as a bone. Yet the fuel smell persist.....on occasion. It is not there every time and does not seem to be related to fuel level in tanks. The odor is gone within a few minutes of opening the door and is non existent after that until the next time it sits closed up for a few days. I have a new Selkirk fiberglass interior and sometimes I think it is the fiberglass I smell but ultimately I still believe it is avgas. No auto gas used.


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I grew up smelling gas in 180's-185. So I thought it was normal. Wrong

The fuel selector valve is a hidden yet a real possible suspect. Some O rings that a pilot can't see, nor even heard about, can be leaking and you won't know it. Till Some mechanic who knows way more than the person flying it fixes it..!

Hope you're not sawing fuel lines. Them valves can be a sleeper for sure. I just thought it was normal, till I was told otherwise.

Kem
 
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I started smelling a fuel smell in the Cessna. Was a backed off primer nut as another poster mentioned. Worth a look. Luckily, not too many junctions for fuel to migrate out.
 
Did anyone mention to take a look at your filler neck adapter gaskets to the bladders or just tighten the screws. A bit of fuel getting in side the fuel bay between the bladder and fuel bay would eventually be smelled elsewhere.

.......assuming you truly have no other leaks......most commonly I find a "sometimes" fuel smell in a Cessna to be bladder nipples deteriorating.
 
Second Dave. Also on late model that have a separate shut-off there is a T under the floor that is hard to touch. Look for blue stains on the belly inside near the console. The thread sealer can dry out over years and seep.
 
I recently had bladders out and all nipples in great shape. What I did find was all of the cavity tape was "melted" and it was a horrible project cleaning all the glue off of the tanks. Yet no evidence of leakage or blue stains. Thinking maybe it was the wrong type of tape i ordered tape from Hartwig as well as Eagle. Same stuff from both places , same as what was in there. This again supports my theory that there are vapors permeating from the bladders that eat up the glue and make their way into the cabin through the wing roots.
I'm going to check torque on plate gaskets as suggested.


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The green fuel bay "duct tape" is a pretty good product. I have to hide it from myself and others so it is not used up on projects where grey tape would suffice.

Also. Have seen a few rigid fuel lines (aluminum) in the belly and doorposts,etc, with pinholes from corrosion.

One of our members had a decent looking 206 with lots of that kind of thing and also a few loose line unions. Of course there were blue fuel stains to betray the leaks.

Let us know what you find. This is all very interesting!
 
I have also found pin holes in the lines above the doors as evidenced by staining (as you mentioned)All replaced. Still too cold here to cap off lines and vacuum/pressure check but I have been over every inch of the supply/vent lines and valve. No staining to be found. Strangest part to me is the hit and miss nature of the odor. Probably right at 50/50.


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Dave Calkins said:
Have seen a few rigid fuel lines (aluminum) in the belly and doorposts,etc, with pinholes from corrosion.
Click to expand...
The collector tanks in 207s are famous for pinholes. They're caused by grit working its way in between the belly skin and the bottom of the collector tank. Any 207 that has spent much time in BET or KSM will likely have acquired loads of grit, so it's only a matter of time before blue stains show up on the fuselage skins aft of the main landing gear. Our spare parts shelves in BET have a number of collector tanks on hand, and most have ten or fifteen pinhole repairs.
 
I had a new 1975 180. On it first fueling upon arriving home when I switched the fuel valve to one tank in order to prevent cross feeding while fueling I noticed the fuel handle rising and lowering each time that it was turned. Upon looking for the culprit I found that each time the handle turned the bottom of the valve mechanism was scrapping on the fuel line to the engine. It had cut two grooves nearly through the tubing, just short of starting to leak. Did you look there?
 
Speedo said:
The collector tanks in 207s are famous for pinholes. They're caused by grit working its way in between the belly skin and the bottom of the collector tank. Any 207 that has spent much time in BET or KSM will likely have acquired loads of grit, so it's only a matter of time before blue stains show up on the fuselage skins aft of the main landing gear. Our spare parts shelves in BET have a number of collector tanks on hand, and most have ten or fifteen pinhole repairs.
Click to expand...

I duct tape all the gaps that let sand get under the floor. A couple weeks ago I put a new header tank in a 206......it had a pinhole in a corner, probably a weld-fissure. I covered the gaps in the floor with that fuel bay green tape that I hoard.
 
8 years. Just had them both out. Both in great shape.


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fuel line under flap quadrant - see pic

1) This was on a 180J. It's the fuel line directly under the flap quadrant. There was a bit of gritty resistance when pulling flaps.
Might want to check under yours?
2) Do you have the oil dilution system? They can develop small leaks, and the fuel drips down the firewall.

flap quadrant cut.jpg
 

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That happened to me with a brand new 1975 180. I had just arrived home from picking up the airplane at Wichita. When I retracted the flaps I felt something rubbing. I looked at the fuel selector handle and it was moving up and down with every flap handle movement. The fuel line had two deep gouges worn almost to the point of leaking. That was a close call which could have been serious trouble had it not been caught. Thanks for posting the picture. As I recall Cessna had a piece of plastic tubing for anti-chafe purposes on that tube. That plastic was sliced right through.

I strongly suggest that ALL of you 180 owners check for clearance between the flap handle quadrant and the fuel line. It's in a difficult to clearly see area. You could be in deep DoDo if this fails in an unfavorable environment. I thought that maybe mine was an isolated incident. But here we are 42 years later and it is still a problem.
 
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By the way, for folks with a fuel smell issue or grittiness in the flap quadrant - it's not that hard to see down there to check the fuel tube that extends under the flap quadrant. You'll have to pull seats, carpet, and plastic around the flap handle/quadrant, but once you have that out it's relatively easy to see down in there with a flashlight. No mirrors or scopes needed.
J
skywagon8a said:
That happened to me with a brand new 1975 180. I had just arrived home from picking up the airplane at Wichita. When I retracted the flaps I felt something rubbing. I looked at the fuel selector handle and it was moving up and down with every flap handle movement. The fuel line had two deep gouges worn almost to the point of leaking. That was a close call which could have been serious trouble had it not been caught. Thanks for posting the picture. As I recall Cessna had a piece of plastic tubing for anti-chafe purposes on that tube. That plastic was sliced right through.

I strongly suggest that ALL of you 180 owners check for clearance between the flap handle quadrant and the fuel line. It's in a difficult to clearly see area. You could be in deep DoDo if this fails in an unfavorable environment. I thought that maybe mine was an isolated incident. But here we are 42 years later and it is still a problem.
Click to expand...
 
It is also possible to see the area quite well through the access panels on the belly. Just need a second person to operate the flaps while looking.


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I don't know where you guys were looking but I had a fuel leak on my 185f and it was a bear to find, see and repair. It was fittings under the floor near the fuel selector.
 
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