Comment

Comment by Brad Payne on March 8, 2020 at 3:48pm

I had the same issue when I had greater the 5 gallons in the tank with the fuel caps supplied by Zenith. 

I suspected the low pressure of the top wing was sucking gas out and creating a vacuum.  After some thought, I decided to fill the tanks and put a few white address labels on the wing behind caps.    When I landed and the white address labels were blue, I knew I found the issue.

Comment by David J. Beaulieu on February 19, 2018 at 9:17pm

Update on the snorkel mod...has resolved the vacuum issue nicely.   Slight uneven fuel flow/use from the main tanks which I will attribute to the plumbed path differences.  Pilot side tank burns/empties a bit faster than the other side.  Pilot side tank has very short run to header with one service valve in flow path.  Other tank has an additional three foot run to the header tank, a service valve and a crossfeed shutoff valve in the flow path.  I think frictional losses thru the longer run and thru the crossfeed accounts for the slower flow from that tank and difference in tank use.

Comment by Doug Malloy on December 27, 2017 at 8:35pm

Hi David--I am curious, since I have the same Skytec system as yours, how did you address the tank vent? Did you cap it? I will be very interested how the snorkels work out. Happy New Year!

Comment by David J. Beaulieu on December 21, 2017 at 3:35pm

Jimmy, based on threads within this forum, I was sensitive to the possibility or whether I also might have an issue with unequal fuel feed from the tanks or of a vacuum being created in the tanks, so on my posflight inspections I would pull out the ladder and loosen the fuel caps.  Noticed, an inrush of air almost every time on both tanks.  I have two 15 gal tanks which feed to a SkyTek header tank which is vented to each tank.  Initially I was not convinced I would have an issue with this system.  Lo and behold, though i do get a bit of uneven fuel use from the tanks, (I will guess that is primary due to my flight patterns) I also consistnely have the same issue that others have noted in this forum.  I am looking forward to getting in a few flights with the fuel cap mod to see if that indeed resolves things.

Comment by Jimmy Young on December 20, 2017 at 5:16pm

I am curious how you discovered the tanks have negative pressure. Is it uneven rates of fuel flow?

Comment by JEFF COCHRAN on December 16, 2017 at 9:39am

I think I have copied almost everything John has done except this.  Maybe I need to do this also!