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  #1  
Old 04-12-2020, 10:34 PM
Jake14 Jake14 is offline
 
Join Date: May 2014
Location: Seattle
Posts: 342
Default fuel odor after looping

I do just basic positive-g acro in my 14, but notice that after a couple of loops (+4 to 0 g) I get a faint smell of fuel in the cockpit which disappears in a minute or so. Don't get this with other maneuvers. I've checked all the fuel system connections but can't find any evidence of leaks (odor or blue stains)
Wondering if this is common or cause for concern and any suggestions where to look would be appreciated
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  #2  
Old 04-12-2020, 11:04 PM
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Steve Melton Steve Melton is offline
 
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I don't loop but you're doing the right thing to find the source of the fuel smell. Anytime you smell fuel, find the source.
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  #3  
Old 04-12-2020, 11:12 PM
Jpm757 Jpm757 is offline
 
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Most likely fuel exiting the vents.
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  #4  
Old 04-13-2020, 12:19 AM
Robin8er Robin8er is offline
 
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Location: Socal
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I have the same problem sometimes on my 8 usually as I approach 0 G's. I think it's from the fuel vents. I checked all my fuel lines and made sure there was no leaks. Mine also only happens during acro.
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  #5  
Old 04-13-2020, 08:35 AM
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Location: Kingsville, Ontario, Canada
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I get this occasionally to but only on the first climb out on real full tanks. After that nothing. Figured it came from one of the vents as there are no other system leaks.
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  #6  
Old 04-13-2020, 11:15 AM
Tom Martin Tom Martin is offline
 
Join Date: Jan 2005
Location: Ontario, Canada
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With full tanks, in the sun, I have found that there is a very small leakage of fuel around the stem of the Van?s standard fuel valve. Check with a small bit of Kleenex at the top of the valve

This is a very tiny amount of fuel, the odour, is distinctive.

Typically it happens about two or three minutes into the flight with full tanks. Changing tanks will eliminate the issue

I have also experienced, occasionally, the fuel smell, from fuel vents, during aerobatics.
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  #7  
Old 04-13-2020, 12:22 PM
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Tom, yes probably the fuel caps. When I fill to the brim and then bring my RV into the heated hanger I can get a pretty good fuel stain in a few days off the left cap - gas expands. I don?t do this anymore.
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  #8  
Old 04-13-2020, 03:32 PM
Jake14 Jake14 is offline
 
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Location: Seattle
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Thanks for the suggestions, I fly with fairly full tanks so I think the vent may be what's causing it. On a pull-up to vertical with plenty of fuel in the tanks, the vent intake at the top/rear/outboard of the tank probably gets submerged. Then the positive g at the bottom pushes the fuel out.
Thanks again.
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  #9  
Old 04-13-2020, 03:46 PM
Norman CYYJ Norman CYYJ is offline
 
Join Date: Feb 2005
Location: Victoria B.C.
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It's a lot more fun to do acro on 1/4 to 1/3 full tanks.
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  #10  
Old 04-13-2020, 03:52 PM
Bavafa Bavafa is offline
 
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Location: Sacramento, CA
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Quote:
Originally Posted by Jake14 View Post
Thanks for the suggestions, I fly with fairly full tanks so I think the vent may be what's causing it. On a pull-up to vertical with plenty of fuel in the tanks, the vent intake at the top/rear/outboard of the tank probably gets submerged. Then the positive g at the bottom pushes the fuel out.
Thanks again.
On your next fill up, try to see if you can lift of the nose wheel and observe. With the 14 tanks, you will get two cups or more of fuel coming out of the vent. The fuel goes to the back and outer corner of the tank where the vent line is terminated at. I noticed this during my phase one and testing.
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