Newton Fuel Caps

[n981ms]

Mine are aligned with airflow and leak.

[Kahuna]

So with some more digging, I have found that there are 2 different retro fitting fuel caps. Both fit and lock into the same receiver. In looking and measuring the receivers, they are the same, but the caps are not.
Mine with the double seal, not 1 of the 4 caps will come out without prying them out. With the single seal cap, they come out easily. I removed the small lower seal and they now come out easily. Caps still seal and in my case fuel still transfers from outboard tank just fine.
Newton has never answered any emails.

[dmaib]

It appears that I have solved the problem of fuel siphoning out of the Newton retrofit caps, sold by Van's, for quick build tanks.

Poking around on Newton's web site, I managed to find the Newton SPRL web site and emailed them a few months ago and explained the problem that many of us were having with these caps. After a few weeks, I got a response from Mr. Robin Voice. Robin decided to send me some parts to update the caps. The parts were a replacement small o ring that is internally located, and the red plastic part on the bottom of the cap.
He sent no instructions, but assured me that it was self explanatory when I took a look at the parts. Well, it was not self explanatory, but I asked him a couple of more questions and finally got up the nerve to try and take one of my caps apart. It turned out to be fairly easy and I got the o rings replaced and the new red plastic piece installed in about an hour for all four caps. The new o rings appear to be just slightly larger than the ones that I removed.
I flew the airplane this morning after topping off the tanks and am VERY pleased to report that the fuel no longer siphons from the key slot.

Robin will be attending Air Venture and said he would bring along some spare parts if others would like them. I would suggest contacting him at Newton SPRL if you are interested.

David "No more blue stains on the wing" Maib

[cbennet1]

Great news! I have yet to install the unused caps I bought second hand. Any way to identify visually if I have good or bad ones?

Craig

[BigglesRV7A]

Fantastic News David and thanks for following this through. I will drop him a line to work the remedy for mine too.

Greg

[dmaib]

Originally Posted by cbennet1

Great news! I have yet to install the unused caps I bought second hand. Any way to identify visually if I have good or bad ones?

Craig

I am not aware of any way to tell if your caps are "good" or "bad". Maybe Robin can tell you. If I were in your situation, I would just get the parts and change them before using them unless Robin can tell you that yours are OK.

BTW, my caps look like the the lower cap in Kahuna's photo in post #22. One big o ring instead of two. I wonder if those with the cap with two o rings have the fuel siphoning issue? That would be interesting to know.

[n981ms]

My leaking caps look like the lower cap with one o ring.

Robin responded rapidly to my email so hopefully I will soon have repair parts.

Thanks David for sorting this out for us.

[Gary 40274]

Is my assumption correct that if you are leaking fuel out that you would get rain in? Not a good situation

Gary Specketer

[dmaib]

I've never had a drop of water show up in my fuel samples, even after parking overnight in rain. I suspect that the caps siphon fuel only when fuel is touching the bottom of the caps and the tanks are pressurized from the vent in flight. So, my guess* is the old o ring was good enough to keep water out on the ground, but was undersized just a tiny bit and would let fuel by when under a little bit of pressure in flight, and with the low pressure on top of the wing to help suck it out.
Also, when filling the tanks up on a cold day and then storing the airplane in a heated hangar, my vents would let a little fuel out as it warmed up(as expected). But, I never had fuel vent out through the key slot in that situation as someone else reported in a previous post.

*I did not stay in a Holiday Inn Express last night so this is a complete WAG

[n981ms]

I also have not found any water in the sump despite my fuel siphoning caps being out in the rain while on a trip.