tc1234c

tc1234c

Well Known Member
Last week I flew my RV9A through rain in IFR condition (yellow and green on radar) for 1.5 hrs. The air was relatively smooth and the air temperature was in the 40s. I left the airplane tied down on the ramp for two nights. The first night it continued to rain then the temperature dropped to the low 20s. When I went back to the airport and checked fuel the left side was clean (the last half an hour I was burning fuel from the left tank) and the right side drain was frozen. In the afternoon when sun warmed up the fuel I drained out three cups (small fuel sample cup) full of water from the right tank. Just wonder how water got into the tank. After I came back to my home airport I took the cowling off and checked the gascolator and found no water in it. Could the water get in through the fuel cap or sucked in through the air vent in flight. My fuel cap has never been serviced over the past four years. I am going to put some fuel lube over the seal.
 
Van's Lockable Fuel cap retro fit

If there is any risk that your leakage is coming through the cap, my suggestion is a retrofit available from Van's, and it also has a key. The caps are made in the UK, and have one or two "o" rings and seal well. I have used them on 2 RVs and recommend them. Current catalog shows them costing $65 each. Easy retrofit, all you need is a little leftover proseal.
 
water in tanks

Every time I washed the RV-4, I found a little water in both tanks and had assumed it was getting in from the fuel caps even though they appeared to really seal well, and I never found any fuel stains around them with inverted flight. Decided to tape up the fuel vents on the next wash, and no more water in the tanks since. That is one possibility.
Bill
RV-4 Slider
 
Toilet bowl plungers

I have heard of people putting toilet bowl plungers over their fuel caps when parking outside in the rain. It might look a little weird (expecially if you decide to leave the sticks attached :D) but it would seem to me that it would work.
 
I have used tape over the fuel caps when left outside on trips. Usually painters tape or electrical tape.
 
This year at Sloshkosh I saw a dozen airplanes in the Sea of RVs with duct taped caps. 6 by 6 inches squares or so. Some of them even had duct tape colors matched :) Will dig for pix.
 
Vlad said:
This year at Sloshkosh I saw a dozen airplanes in the Sea of RVs with duct taped caps. 6 by 6 inches squares or so. Some of them even had duct tape colors matched :) Will dig for pix.
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I used white 3M PVC electrical tape from Lowes. The color matches almost perfectly the "Marathon White" AcryGlo paint on the RV-8. Also worked well sealing the forward baggage door seams and hinge lines to keep the rain out of the baggage compartment.
 
Boelube up the center shaft of the fuel caps. This was recommended to my by some "old timer" rv builders. Works great. I never get rain in my tanks and in fact the caps hold water under the little latch. Of course I always check very, very carefully after leaving the plane outside overnight and/or in a rainstorm.
 
Jamie said:
Boelube up the center shaft of the fuel caps. This was recommended to my by some "old timer" rv builders. Works great. I never get rain in my tanks and in fact the caps hold water under the little latch. Of course I always check very, very carefully after leaving the plane outside overnight and/or in a rainstorm.
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Exactly - the van's caps have _two_ orings. A little one inside and the big outside one. They both need fuel lube or somesuch. I've left my RV out in some serious rain and never had water get in.
 
leaky gas cap

Some yrs. ago I had a -4 and it set outside during 12" of snow. When it melted, I found a cup of water in one tank...culprit was the gasket...Replace or grease it. :)
 
Ron Lee said:
I have used tape over the fuel caps when left outside on trips. Usually painters tape or electrical tape.
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Same here.

When the airplane is outside over night, like at OSH, the fuel caps get taped. It's almost impossible to know when and if they will admit water, had it happen one time and that did it forever. I do not trust them.

(Long live under wing single point refueling - which of course does not exist here)
 
Water thru airfilter

While on the subject of water and fuel, be also mindful if you leave your plane out in the rain and if water can get in thru your air filter (horizontal induction) . I have drilled a small hole at the bottom of my snorkel so it can drain itself as once my plane was sitting out in the rain and I had a fair amount of water in the snorkel. Luckily I found out about it before taking off.
 
This afternoon I slowly poured half an gallon of water over the fuel cap, waited several minutes then checked the fuel drain. There was no water in the tank. I put on some fuel lube over the o-ring just in case. In my case it is very likely that water came in from the vent.

As for the air box I do have a small hole drilled at the bottom.
 
This would be a good way to test

ArVeeNiner said:
I have heard of people putting toilet bowl plungers over their fuel caps when parking outside in the rain. It might look a little weird (expecially if you decide to leave the sticks attached :D) but it would seem to me that it would work.
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This would be a good way to test for leaks in our fuel caps. If the plunger sticks there is no leak. If it fills with air and falls off, air would be coming though the vent and through the cap. I have not tried this, but I think I will.
 
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