D

dnjfletch

I'm New Here
Recently got my 8 flying. In fact, have finished Phase-I last weekend. When I pull G loads, either negative or positive, I smell fuel odor in the cockpit. When a friend flew it for the first 4 flights, he made a comment about it on the radio and somebody flying in the area made a comment that the odor was common for RVs. Has anybody else noticed this, and if so found its source? Seems like a regular old leak would do so all the time, not just under G loads.
 
Two common sources I'm aware of:

  • A leak by the fuel selector valve. Check for dye.
  • Not 'g's per se but on the 6 & 7s (and 8 as well?) when doing a loop sometimes I could get a little bit of a fuel smell. The source was the fuel going out the vent lines and then seeping back in next to the vent fitting. I removed the vent fitting nut, added a little RTV (to make an ad hoc gasket), replaced the nut and the problem was solved.
 
I get it every time I get less than .5G. Only time I've ever smelled in positive was a lot of positive (+4G) with a tank vent that was spitting on the ramp just before take off.
 
mating surface

Pull the lines apart and check the mating surfaces between the lines and fittings. Had an intermittent leak on a 177 that had an imperfect mating surface problem on the hoses.
Best
Brian
 
A very common source of the fuel smell in the -8 is flying th pattern with a REALLY full tank - excess fuel blows out the vent, and sweeps back into the under wing NACA scoop - the fuel smell comes in the passenger's vent, and while the pilot can smell it, can't easily localize the source.

May not be the same thing you are experiencing, since you seem to associate it with "G's", but thought I'd mention it as "normal". The answer is to burn a little off each tank as soon as possible before entering a pattern.

Paul
 
Steep climbs with full or almost full tanks will cause fuel to puke out the vents also. I'm sure I lose a bit of fuel in the winter when making 80 knot climbs!
 
hole in vent line

A friend of mine was doing some acro and could smell fuel.....stop the acro and check this out......could not find anything, smell went away. Did some more acro and a drip on his knee...aha....investigated with a couple of fingers and voila...wet fingers (did I just say that)....anyway what had happened is something had sawed a neat well hidden hole in the vent line.....no problem when everything positive and in place but a few neggies and the hole gets unsealed and fuel in cockpit......might be worth checking out..
 
fuel smell

Both my RV4 And My RV6 have had this. Not a problem! Some times in turbulance or aerobatics, some times on a warm day, sometimes for no reason at all I get a strong fuel smell in the cockpit. This has spanned over 2100 hours in 2 RV's.

What has caused this is, a little fuel to goes in to the breather and from internal pressures, then it splashes down the belly. The vapor gets sucked in the hole for the flap actuator, and thus vapor in the cockpit.

Steve Barnes "The Builders Coach"
 
Marc DeGirolamo said:
...something had sawed a neat well hidden hole in the vent line....
Click to expand...

I had smelled fuel intermittently for years on our -4, but checked all the lines and never found any leaks. Doing the inspection this year I was looking down from behind the instrument panel and something didn't look right. It was hard to focus on because everything was the same color in a dimly lit area. Finally it dawned on me that it appeared that the rudder cable was inline with the fuel vent directly behind the bulkhead. Pulling the vent to the side showed that it was nearly sawed through. Easy fix, but hard to spot.

cable%20saw.jpg
 
Ditto

DNJFletch, WELCOME to VAF!

I've experienced the same thing, and it's bothered me to no end. Like you said, it's intermittent, but pretty consistent with acro, even the occasional steep turns and rolls and nearly always present right after fill-up.

At the condition inspection, I found a couple of fittings that were damp and stained blue -- the right wing root fitting and one of the fuel selector fittings. They've been bone dry ever since, but the smell continues.

I crawled in with a mirror and flashlight over the weekend and thought I saw some dampness in the vent fitting inside the left gear tower -- BUT CAN'T GET TO IT! Seriously. With the wires, cables and vent lines inside, it's not possible to get my hand in there to even check the fitting. I did manage to swipe a clean paper towel in a long clamp-gizmo, and it came up clean. If I had it to do over, I'd enlarge the lower hole into an access panel like others have done.

The smell is bothersome and I wish it would go away. However, if it's a common problem and not one that presents any real hazard, I could learn to live with it, I suppose.
 
Just to make sure that folks don't get the wrong idea about fuel smells....whiel I am 99% certain that it is common to get the fuel smell the way I described it in an RV-8 with full tanks (vented fuel flowing past the NACA vent), i would never take ANY fuel smell in the cockpit for granted, and would chase them down. When we re-did the interior and panel in Louise's -6, we had a faint fuel smell on the first couple of test flights - turned out to be a nick in the flare of one of the new lines I fabricated for the fuel flow 'ducer. Yup, the fitting was wet.

It's great to ask the questions and track down the cause - and a really good idea to KNOW that what you are getting is normal or not. That pic of the sawed-through vent line is pretty interesting.

Paul
 
Thanks for the great info everybody! I will start checking these various possible causes while working through the other sqwacks. I agree with IronFlight that fuel odor in the cockpit shouldn't just be accepted as normal.
 
While I was installing some aluminum pieces on the cockpit side walls to make pockets to hold various 'stuff' while my wife and I are flying, I crawled all the way in on my knees and got a mirror to where I could see the spaghetti bowl under the fuel selector valve. And guess what, blue dye! Hopefully it is just the tubing nut that needs tightening, because I can probably do that in situ. Otherwise taking it apart will be a pain. Thanks again for the info guys.
 
Dave,

A year after I bled my brakes I had discovered a speck of red dye under the nut. Disassembled, trying to figure out what's wrong. The tube was flared a hair more than needed and then over tightened. A micro crack has developed on all circumference as a result. Very difficult to see. May be applicable to your situation.


badflare.jpg
 
You must log in or register to reply here.