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Newton Fuel Caps

dmaib

Well Known Member
I would like to know how many folks have installed the Newton fuel caps that Van's sells as a retrofit for tanks that are already built. It seems that most, or all, of these that are installed on RV-10's have an issue with fuel venting out the key slot in flight when the tanks are filled to the point that the fuel is in contact with the bottom of the cap.
I talked to a Harmon Rocket owner/builder a couple of weeks ago that had these caps and he says he gets no fuel siphoning out the key slot and always fills his tanks to the top.
So, I would like to know if this is a problem specific to the RV-10, or if those who have installed them on other RV models have the problem.
 
Retrofit Newton fuel caps leak

Hi David,

I installed a set of these caps and have not been at all happy with them. As you have indicated the issue with them leaking out the top of the cap is a concern with full tanks. In addition to this I filled my tanks (2-3 litres from full) on a cool day and later in the week with my plane hangared, they leaked through the cap on a very hot day with fuel expansion and have ended up staining my PPG paint. Obviously it was easier for the fuel to vent through the cap than through my vent. I have tried using fuel lube inside the cap also without success to seal them through the key mechanism.

The other thing you need to be aware of is that Newton changed the profile of their caps without letting anyone know. How I know this is I wanted to have mine engraved and rather than ship over my installed set to the States, I decided to have a new set from Vans sent to the Engraver (at Independence Airpark) The engraver did a fantastic job and then shipped back to me here in Australia. When I went to install them, the caps sat 1/4" low in the receptacle. After much dialogue with Newton, I had to purchase another set from them with the same profile set-up as my originals even though they are listed at Vans. Even the two I had engraved were differing profiles in so far as one had one 'O' ring and the other had two 'O' rings on the seat. When I spoke to Newton about it they said it was their right to improve their product and hence I had no comeback on customer service.

Long story short, yes they pass fuel out the cap.!! :eek: If I fill my tanks to full, in flight with the fuel vent pressured, it leaves a blue stream over my wings and over my flap.:(:(:(

Cheers, Greg Blakey (FADEC IOF-360 WW200RV)
 
Newton fuel caps

David,
I have the Newton caps and have no problem with them leaking out the key slot or around the seal and I top off to the point of overfilling at times. I have 550 hrs on the plane. I would contact Newton about them. The one thing a cap should not do is leak.

Don
 
Are they retrofit caps?

Don,

Do you have the exact (retrofit) caps that David is referring? Newton also make caps where the receptacle has to be installed with the tank build and these caps seem to be ok. It is only the retrofit with the insert collar that I have had issue with. Exactly the same as in his link above.

Cheers, Greg
 
I have the deluxe locking caps from Vans. I installed them during tank build. They are not the retrofit ones David is referring to. No leaks so far. Does Newton have any idea why they are leaking? Maybe when I come down end of May, we can compare the retrofit to new install model to see where the differences are.
 
I have the deluxe locking caps from Vans. I installed them during tank build. They are not the retrofit ones David is referring to. No leaks so far. Does Newton have any idea why they are leaking? Maybe when I come down end of May, we can compare the retrofit to new install model to see where the differences are.

I sent an email to Newton a while back explaining my problem and have had no response.
 
David,
Yes, I have per plans vents, 90 degree bend with the angle facing forward.
Don

Thanks Don. Well, that really makes me wonder if there was a batch of caps with a problem. I guess I will keep trying to communicate with Newton and see if they respond. Perhaps I should call Van's, too.
 
I have em (on 4 tanks in my 8) and they dont leak from the key hole.
I have had trouble that they can be hard to pull out for fueling. I keep em fuel lubed (Hate that junk). Takes pulling and prodding on the key to get them to pop out and Im sure Im wearing them down somehow. My buddy Leggs has em too. Ive tried his caps in my tank and they go in and out easily. Argh. I have no idea how all 4 of mine are hard to get out and his go in and out of mine and lock easily on all 4 of my tanks. There is nothing to screw up on installation. :confused:
I do not have stock vents at all so no comment there. Mine must seal very well or I will run out of fuel and be a statistic... so the sealing is very important to me. They seal very well.
 
I have em (on 4 tanks in my 8) and they dont leak from the key hole.
I have had trouble that they can be hard to pull out for fueling. I keep em fuel lubed (Hate that junk). Takes pulling and prodding on the key to get them to pop out and Im sure Im wearing them down somehow. My buddy Leggs has em too. Ive tried his caps in my tank and they go in and out easily. Argh. I have no idea how all 4 of mine are hard to get out and his go in and out of mine and lock easily on all 4 of my tanks. There is nothing to screw up on installation. :confused:
I do not have stock vents at all so no comment there. Mine must seal very well or I will run out of fuel and be a statistic... so the sealing is very important to me. They seal very well.

Mine come out and go in very easily. Do your buddy's leak out the key slot?
 
I have them and love them. No leaking and mine come in and out very easily ... never did anything to make them that way ... just does !!

Leggs
 
Newton Retrofit fuel caps.

I have retrofitted Newton caps on two of my RVs and found them to be totally trouble free over many years. They have never leaked.

My experience is that they can be a little difficult to remove due to a tight "O" ring fit, but no big deal.
 
I really appreciate all of the input from folks using the Newton retrofit caps. So far, I can't see any glaring reason why some of them leak through the key slot and some don't.

I've sent emails to Van's, Newton Equipment, and Newton SPRL, who is apparently the "aviation department" of Newton Equipment. So far no responses.
 
Fuel lube seems like a good idea on the rubber part of the caps, but I just spent an hour or more mopping out the tank on a T-18. That fuel lube had formed blobs under the filler, and also was in the low point in the tank.
Only a PITA on a T-18 tank, it would be very difficult to remove from a VANs wing tank because of the ribs.
 
Dave, just another data point. I've had the newtons for about five years. One cap has never leaked. The other cap has always leaked. Initially I swapped it out with a new one from Vans but that one leaked too. I then swapped it out with another new one from England. That one leaked as well! So I've just learned to live with it. One leaks, one doesn't. Personally I wish I had never installed them. Just my .02.
 
When I was pressure testing my fuel tanks I found that I could not get a seal at the standard vans fuel cap....they leaked something terrible. I tried taping over the caps with various tapes but the pressure would just cause the tape to lift.

As I already had the retrofit Newton caps in stock I installed them to see if the seal was better. One was a perfect pressure proof seal (24 hour very accurate manometer test)...the second Newton cap was less leaky than the Vans cap but would not hold pressure.

So there you go. One perfect seal and one not so perfect....but both Newton caps were a better seal than the standard Vans caps (which in my opinion are quite terrible).

Also, no problem with the fit of the Newton caps....very easy to use....just turn the key and they lift out easily.
 
Alignment question

Really dumb question for those that installed the retrofit caps. Wondering if you installed them with the key slot aligned with the airflow or perpendicular to it. Looking for any possible explanation for the fact that some leak and some do not. As best as I can see from the available posts we have no answer from Newton.

Craig
 
2 different caps

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.
newtoncompare2.jpg
 
Solution

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.:D

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
 
Leak solved?

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
 
Sensational News!

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

Greg
 
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.
 
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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.
 
Fuel out-water in?

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

Gary Specketer
 
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:)
 
Water in?

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

Got my new parts from Newton. Went pretty easily. I have not filled and flown them yet but as you can see there is a definite size difference in the O-rings. I did not measure them.
35cg0ls.jpg

You can see the keepers (4 orange flanges arranged around the center) pushed out of the way. I did it with a small flat head screw driver. Once pushed well out from center the orange plastic slides off with a tug. It did not seem spring loaded or try to fly apart.
Here is a picture mostly disassembled.
rmka6w.jpg

Here is the barrel with the O-ring on it
2ykz9k0.jpg


The new orange piece just slides back into place with a click. Be careful to have all your parts including the spring reassembled before you click it in though. It would be difficult to remove the orange piece in such a way to be reusable.

I hope this helps someone.
 
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Excellent photos Maxwell. Thanks for putting them up for everybody. I can report that my caps are still leak free after about 15 hours of flying. I fill 'em right up to the top now! :)
 
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