hydroguy2

hydroguy2

Well Known Member
Kinda makes you nervous when you smell fuel with under 5hrs on a new engine/airframe.

I topped of the tanks today to do fuel burn calibrations. I launched from RY16(3890msl), straight out and climbing ~2000fpm 115mph, shallowed the climb to about 1000fpm 145mph. Leveled off at 7500, and as speed increased to 175 it was getting pretty rough. I am still trying to breakin the engine, but no way I'm going to be able to run 24sq. The mostly cloudy skies opened up to the south, so pointed her to the blue.
As I climbed thru 8500' things smoothed out real nice, at 9000' climbing 1000fpm....I smelled fuel, Fairly strong considering I have lots of air coming under my canopy edges. Surprised I'm 15miles south of the airport at 9300' 22.9" 2400rpm I was indicating 175 and 400fpm climb. Quick call to my buddy telling him I'm returning to the field. I make a 180, switch tanks... everything good, smell is gone. But I'm nervous, and touchdown a little hot and balloon up, a tiny bit of rpm and she settles on nicely.
Once on the ramp I shutdown and inspection showed nothing. Pulled the upper cowl and nothing indicated.

My hope is full tanks, bumpy ride and/or climb sloshed some fuel out a vent.

Any ideas or help?

Then after I had a late lunch and thought about things I went back to the airport, went back to check fuel levels. Right tank was down ~2" from full. I only ran this for 10 minutes. No loose fittings, so wonder if I siphoned some out. Unable to find anything, I figured I may as well take her up again to do a sniff test. Run up good, climbing again at roughly 2000fpm and shortly later got a faint whiff of fuel.....level off, nothing.... switch tanks, nothing. zoomed around for 1/2hr, with a couple shallower climbs and nothing noteworthy....except the truly fantastic performance I experienced!

WOW. these little planes are wild.
 
Once is a coincidence, twice is a trend. I'd do a thorough check of all the plumbing running through the cabin and firewall. The tricky thing with Avgas is it evaporates so fast it can be hard to find.
 
I have a 7A and have never gotten so much as a whiff of fuel in 6 years. You need to find the source before you fly anymore IMO.
 
Saturday will be tear down day. Other than pulling up the carpet today, I haven't had the interior apart since first flight so now's the time. I put a wrench on all the fittings after engine start and before first flight but not since.
All part of the phase 1 I guess.
 
Fuel odor

Just finished my phase 1 yesterday. The 3rd and 4th flights I also experienced a fuel odor. Tracked it down to a fitting between the electric fuel pump (injected engine) and firewall. If enough to smell in a flying RV, it is enough to leave a stain. This past week I also found the cork gasket under the access plate in the right tank seeping. Thank goodness there is enough room to tighten screws and dab on some more proseal. Keep looking till you find it.
 
If there isn't enough to leave a blue stain, it will leave a very light white residue (was a ramp rat in my high school days). To see what I'm talking about, put some on your finger and watch it evaporate, then wash your hands. You could try a soft black glove or t-shirt, and wipe your finger around all the suspect areas until you find it if you don't find any blue dye.
 
Congratulation on your build

I agree, if you smell fume, there is probably some leaking.

Once in a long while I would have a small hint of fume and every time I looked for it I could not find any stain, till one day I looked at my tank and sure enough there was very little stain around the screw that hold the float gauge. Tightening those fixed the problem and have not had the smell ever since.
 
I too just finished phase 1 and about the 5 hour mark found a fuel fitting that was just weaping. I too had checked every fitting before first flight, I think it just settled in for lack of a better term and needed another tightening.

I have also found more so when the weather was warmer, that if I fill my fuel tanks to the rim and leave the airplane in the sun. I will have fuel running out of the vent fittings from the expansion of the fuel. I have even noticed this from the fuel tanks to the hangar on a hot day.

I too would take a very good look at things as I don't remember ever smelling fuel in the cockpit.
 
I Get an Occasional Whiff of Fuel

I get an occasional whiff of fuel in my plane and have yet to find any weeping despite lots of looking.

Hans
 
Back when we rebuilt Louise's RV-6 panel and interior, we remade a couple of fuel lines in the cockpit to install the Flow sensor. During flight tests, we got a little fuel smell, and took things apart to find it. Turned out to be a scratched flare face - a bad flare. the moral is that tightening a flare fitting won't necessarily stop it from leaking if it has a surface defect.

This happens most often when the flare tool is used without a drop of lubricant on the tube before flaring (in my experience).

Paul
 
Put some talcum powder around the suspect fuel fittings in the cockpit. It will turn blue if there is seepage. If not vacuum it out...
 
A kleenex works great for spotting fuel leaks. Just touch fittings, if there is any fuel the blue will wick up the tissue immediately.
Also, if you are using the standard Van's fuel valve it can leak under the scenario you described.
With full tanks you take off and climb on one tank. As the sun warms the not used tank, and or, the vent slightly pressurizes this tank, there is a pressure built up in the valve from the unused tank. This can cause a very small amount of fuel to leak our around the fuel stem. This will cause the smell.
Standard operations for me is to run a couple of gallons from one tank for take off and then change tanks. This relieves the pressure in the other tank and eliminates this small leak.
I have had this happen on a few planes, it is not unusual.
 
hydroguy2 said:
...As I climbed thru 8500' things smoothed out real nice, at 9000' climbing 1000fpm....I smelled fuel, Fairly strong considering I have lots of air coming under my canopy edges. Surprised I'm 15miles south of the airport at 9300' 22.9" 2400rpm I was indicating 175 and 400fpm climb...
Click to expand...

Brian, this has nothing to do with fuel smell, but maybe something to do with engine longevity.

I was told to not climb above 7000' during the first 10 hours or so of engine break-in, because the engine can't generate the 75%+ power at higher altitudes that it needs to properly seat the rings.

I'm no mechanic, so maybe someone who knows more can offer an opinion. However, you might want to look into the validity of that before climbing too high again. Just an observation ...
 
I understand the power requirements.my problem is going to fast for the turbulence down low. Been running 24" 2450 rpm between 7500-8500

Engine guy said I'll be fine. Yesterday was real rough so my plan was to get level at 9-9500. I can still pull over 22" and 2650. Again engine guy says "it's a lycoming, it'll be fine.

So far I haven't lost 1 qt in 5hrs, and most of that was the first 20 minutes
 
Brian,

I found small leaks at the bulkhead fittings where the fuel vent line goes through the bulkhead before looping up in the front corners. I got this early on only when the tanks were full and fuel got pushed into the vents and would sit at the low spot (bulkhead fitting). It would go away when I started using fuel from that tank because I was then pulling air and fuel through the vent and into the tank, thus eliminating the fuel in the low spot in the line. Bottom line was a not-quite-tightened flare fitting.

greg
 
I was told to not climb above 7000' during the first 10 hours or so of engine break-in, because the engine can't generate the 75%+ power at higher altitudes that it needs to properly seat the rings.
Click to expand...

Man, thats gonna be hard on my prop, I live @ 7200.
 
Fuel venting during steep climb is normal

Brian,

If you are climbing at 2000'/minute with full tanks, there is probably fuel venting from the tank. This would be expected, as the remaining air in the tank is wanting to expand as you climb. With the steep deck angle associated with that climb rate, the tank end of the vent is probably submerged in fuel. Any un-coordination (off center ball condition) would exacerbate it on one tank.

Given the position of the vents on the belly, it is not surprising that you would smell some gas in the cockpit. If it does not do it during steep climbs with reduced fuel, you probably confirmed the cause.

Obviously, rule out any system leaks as well.
 
gas smell

I had an occasional gas smell on my 25 year old 600 hour RV-4 and it was the fuel sending unit bakelite insulator on the unit. It was weeping in the joint between the wing and the fuselage and coming in around the fuel line where it comes into the fuselage.
 
My initial thought was exactly as Alex stated and I also have experienced this in my RV's. However to be safe you should check all fittings before flying again.

Pat
 
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