Mike /David,
Never use any silicone in fuel tank
applications, you will have residue and the residue will plug your filter
lines- don't ask me how I know.
Use/ make nutplates with sealed nuts (
dome nuts or covered nuts - better still SS long nuts with the ends
welded-up ) and the proseal would be better than RTV.
George ( down under)
Mike,
I have long had a fuel smell in the cockpit and have traced down
several culprits. Each one made improvements, I have finally solved most
of the issues. I know these will not all apply to you, but I am sure
some will. I'll put them in chronological order here, but the ones in
bold most likely apply to you. Luckily, the 2-stroke oil we put in the
gas leaves a telltale residue after it builds up long enough - makes tracing
these leaks much easier. And get in there with that sniffer...
-Small leak at AN-flare from left tank to fuel selector. fixed by
re-securing
-Small leak at at fitting just downstream of fuel pump.
-small leak at fuel pressure sensor NPT fitting.
-While running normally aspirated I was getting a strong
smell in flight. Tracked that down to mostly the pax fresh air
inlet.
This eventually traced to the intake system. Seems that even
in full bore flight, fuel from the secondary injectors (8" from
inlets) would come backwards and mix with cowl air, some of
which would seep out the cowl seam, which was right ahead of the pax fresh air
inlet and blowing right into Anne's face. She kept smelling really
strong gas "making her sick." To me it was not quite that strong and I
thought she was over reacting until I leaned over and smelled the pax air
inlet - sure wish I solved that issue before flying Anne to Vegas.
Solved this by re-installing some of the turbo intake piping to catch any back
migrating fuel.
- Very faint smell but quickly accumulating residue (oil would pool in
the recesses on top of the engine) from fuel leaking out through a
welding defect in the intake runners - fixed with JB Weld. It still also
gets out around the axle in the throttle body while running higher than
ambient MAP. I don't know how to fix that one.
-There is a small leak in the fuel vent
tubing system that runs through the cockpit, but I have not
been able to find the exact location so I will still smell it a little if I
start to vent fuel on a hot day.
-This year my port side fuel tank gasket (the cork one)
started leaking quite a bit around the screws that hold the plate in
place. This required removal of the entire fuel tank to get
proper access because I had previously tried unsuccessfully to seal around
those screws with some sort of epoxy putty. When you think about it,
there is no gasket to keep fuel out around those screws. The fuel can
get past the threads of the nut plate, bypass the gasket altogether, and get
out around the head of the screw. 75% of those screws had 2-stroke
residue. Fuel vapor from that wing root area easily gets into the
cockpit in flight through the openings for the aileron pushrods and control
column. I fixed that one by replacing the cork and putting some proseal
under the head of each of the screws - though I wish I had used RTV.
That proseal will be a real beotch if I ever need to get that plate off
again.
-I also found a number of very small leaks (residue) past a number of the
rivets on the quick build fuel tanks. In particular, the blind
rivets on the back side just ahead of the spar were prone to leak
(about 6 of those had some amount of 2-stroke residue). I put dabs
of proseal around each offender. I don't know if that fixed it (would
need to remove fuel tank again to check) but the leaks were small enough to
not really be a problem.
- On one cross country flight I nearly gassed myself with a dirty
rag. Some pump operator had spilled massive amounts
of fuel over each wing. Actually that happens almost universally
whenever I let anyone else "top it off" as those RV tanks go much faster when
near full. Now I always either do it myself or specify the number of
gallons to put in each tank. Anyway, there were no rags at the pump so I
used one of my own and without thinking I tossed it in back. Passing
through 10,000 ft the smell was so strong I was about to puke before I finally
was able to reach the rag and seal it in the ice chest. Smaller amounts
of spilled gas on a rag make less obvious sources of faint fuel odor.
- I bought a nifty little go-ped scooter that fits in the back of the -6
and is fun to use around airports and for small trips. But on my last
cross country I thought I had developed some new (and strong) fuel leak
until I realized that the tank on the go-ped was probably venting as I went
higher.
Hope that helps :-)
On Fri, Sep 25, 2009 at 7:48 PM, Mike Wills
<rv-4mike@cox.net>
wrote:
This is one of those frustrating little issues.
In ground running I dont notice it, but in flight I smell gasoline in the
cockpit. I've run it on the ground trying to detect leaks and cant find any
at all. Anyone got a suggestion for some sort of a sniffer or telltale I
could put at all the connections that would show evidence of
leaking?
Mike Wills
RV-4
N144MW