Fuel Tank Venting

mwc

Member
So I have had the loud popping coming from the fuel tanks on my cyclone as others have stated. I never thought they were vented well or something. I was under the RV today and seen a black hose hanging down near the back tank. It was plugged up with mud so i cleaned it out. I traced the line and it came out of the top of the larger 30 gallon tank so i assumed it was a vent hose. Upon looking at the hose line, it was basically in a knot held together with a wire tie just where it came out of the top of the tank. No way it could vent with the hose all kinked. I cut the wire tie and straighted the hose out, pressure came out of the tank pretty rapidly. Seems like it will vent now and not pop/ boom all the time. My question is why would this hose have been tied up like this in the first place? Was there a reason for this from the factory?
 

Flick

Well-known member
So I have had the loud popping coming from the fuel tanks on my cyclone as others have stated. I never thought they were vented well or something. I was under the RV today and seen a black hose hanging down near the back tank. It was plugged up with mud so i cleaned it out. I traced the line and it came out of the top of the larger 30 gallon tank so i assumed it was a vent hose. Upon looking at the hose line, it was basically in a knot held together with a wire tie just where it came out of the top of the tank. No way it could vent with the hose all kinked. I cut the wire tie and straighted the hose out, pressure came out of the tank pretty rapidly. Seems like it will vent now and not pop/ boom all the time. My question is why would this hose have been tied up like this in the first place? Was there a reason for this from the factory?

Every fuel tank has to be vented either with a vent tube or a vented fuel cap. There should probably be no exceptions except for vehicles with a fuel vapor recovery system, in which case the venting is automatic. You asked about the vent hose being tied in a knot. I believe that the factory would do this to insure no water would back up into the tank. I would guess it was more of a loop which created a kind of a trap and was tied up with the tie to keep it in place. The mud was a result of mud dabbers which will find their way into any small openings and build nests. We have a lot of problems with them in hoses that vent the rear axle, etc.
 

mwc

Member
Yeah i knew the mud was from the bugs. And yes Flick, you were right, the hose was more in a loop than a knot and it was done intentionally from the factory. How would water get into that hose? Why would they have a loop so tight that it doesnt vent? I undid the loop and it vents great now. Do you think I will have any problems with the loop removed from the line?
 

Flick

Well-known member
Yeah i knew the mud was from the bugs. And yes Flick, you were right, the hose was more in a loop than a knot and it was done intentionally from the factory. How would water get into that hose? Why would they have a loop so tight that it doesnt vent? I undid the loop and it vents great now. Do you think I will have any problems with the loop removed from the line?

I reckon that water could be forced up the vent hose while traveling on wet roads. In this case, a loop would stop it from going into the tank. Would it make it to the tank without the loop? Probably not, in my opinion, but the loop, by creating a form of a trap, would more than likely keep this from happening. I certainly agree that if it’s a tight loop, it could cause a problem.
 

Dahillbilly

Well-known member
Easy fix in my opinion would be installing an in line fuel filter in the line. This way air could enter but the bugs would have an extremely hard time getting in.
 

mwc

Member
Good idea on the fuel filter!
Also, i have not found a hose or any vent on the smaller tank. Its harder to see the top of it though.
 

porthole

Retired
Same problem on on 2010 Cyclone, but we only had one tank. Rerouted it with a loop up high (secured to the bottom of the garage floor) and added the fuel filter. Problem solved.
 

akfoote

Member
New Cyclone owner here, 2021 unit.

Wondering if this issue would be causing my 30 gal to not fill?

Just thinking here.
This wasn't my original issue / why I hopped on the forums .. but the thread title got me :D
 

Flick

Well-known member
New Cyclone owner here, 2021 unit.

Wondering if this issue would be causing my 30 gal to not fill?

Just thinking here.
This wasn't my original issue / why I hopped on the forums .. but the thread title got me :D

Yes, it’s likely you have a venting problem. Air volume inside has to be able to be pushed out.
 

akfoote

Member
Well I just crawled under there here in freezing TX ;)
Nope .. no "tied" vent tube.
You must be correct though there is something going on.

I need to figure it out somehow.
 

porthole

Retired
New Cyclone owner here, 2021 unit.

Wondering if this issue would be causing my 30 gal to not fill?

Just thinking here.
This wasn't my original issue / why I hopped on the forums .. but the thread title got me :D

Causing it not to fill or not to fill all the way?
 
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