Author Topic: fuel cap orings and uneven fuel  (Read 1037 times)


fuel cap orings and uneven fuel
« on: June 15, 2017, 10:04:31 AM »
Like most Helios, mine seems to burn the fuel level in the right tank down to about 1/4 before the left tank moves off full.  There are several possible explanations for this including an air leak at the left fuel cap.  Does anyone know the correct oring type and size for the fuel caps?  The ones in currently in my caps are white.  I realize that uneven fuel comsumption side to side is common in Helios but I am trying to track down things that could exacerbate the issue.

If for some reason the fuel from the left side was blocked I wouldn't know until I was down to 7.5 gallons on the (only available) right tank.

There are some other possible explanations like the turn coordinator not being perfectly level producing a high wing with the ball centered.

Kevin Dunn

Re: fuel cap orings and uneven fuel
« Reply #1 on: June 15, 2017, 10:54:35 AM »
The o-ring number for the Helio fuel cap is MS29513-226.  Make sure you check the vent system carefully for restrictions. 



Re: fuel cap orings and uneven fuel
« Reply #2 on: June 16, 2017, 11:31:32 AM »
I assume this is referring to the Shaw Aero caps. Don't forget the small shaft o-ring. That's the one that is usually the culprit and many don't realize it is there. It is an MS29513-010. I like to check them every year or so, installing with a little fuel lub. Jim


Re: fuel cap orings and uneven fuel
« Reply #3 on: June 17, 2017, 09:03:35 PM »
Thanks Jim and Kevin, They are Shaw Caps and I don't think the orings have been replaced since I have owned the airplane which is over 10yrs.  Two more questions:

Do you have a part number (or source) for the clips attaching the caps to the bead chain and the bead chain to the fuel cap retainers?  Four of mine look different from the other four.  They are not listed in the parts book.

Is it unusual to have 1/4 tank on the right side and over 3/4 tank on the left?  What is normal?