One Fuel tank is pressurized

Ask Questions and Offer Advice Related to the Cessna 120 & 140 Type
Forum rules
You must be a member of the Cessna 120-140 Association in order to post new topics, reply to existing topics, or search for information on this forum. Use the "Join" link in the red menu bar.
8474
Posts: 313
Joined: Sat May 25, 2019 12:08 pm
Name: Blaine F
Location: Saskatchewan
Aircraft Type: C140A
Occupation-Interests: Helicopter Pilot
Contact:

Re: One Fuel tank is pressurized

Post by 8474 »

"The 140a system should normally vent through the tube in the center of the cabin, so, even if both caps failed to vent there should be no pressure."

Yes, as John states "normally" but since there is the chance that the vent on the cabin roof could potentially get plugged they ( FAA) said you need a backup vent, that why the one way valve fuel cap. One way meaning will let air in, but not fuel out.

Also to clarify, that cap that you show in the picture is only required on an A model, if you don't have an A model which by the serial number I'm sure you don't, then you have the wrong fuel caps.

As John said, you really need to figure out what is going on there....
2066
Posts: 600
Joined: Tue May 01, 2018 7:00 am
Name: Mac Forbes
Location: North Carolina
Aircraft Type: '46 Cessna 140
Occupation-Interests: Retired - Current 120-140 Assoc. NC Rep.
Contact:

Re: One Fuel tank is pressurized

Post by 2066 »

...probably not at issue here, but there have been a few owners who have "modified" their tanks and venting (...connecting, changing the selector and caps) over the years sans "approval" without realizing the potential for disaster. Mac
rfrederick
Posts: 28
Joined: Fri May 22, 2020 8:28 pm
Name: Rick F
Location: 5M3
Aircraft Type: C140
Occupation-Interests: IT
Contact:

Re: One Fuel tank is pressurized

Post by rfrederick »

Well John,
you were correct sir. Seems I was opening the same tank first every time, releasing the pressure (positive).
Yesterday I verified that both tanks had positive pressure. I attached some pics of my actual fuel caps and selector.

Thanks again for all the help.
selector.jpg
selector.jpg (221.49 KiB) Viewed 4673 times
fuelcap.jpg
fuelcap.jpg (82.71 KiB) Viewed 4673 times
Rick
M20C/BC12D/140
8474
Posts: 313
Joined: Sat May 25, 2019 12:08 pm
Name: Blaine F
Location: Saskatchewan
Aircraft Type: C140A
Occupation-Interests: Helicopter Pilot
Contact:

Re: One Fuel tank is pressurized

Post by 8474 »

Those are the wrong caps, those caps are specific to the A model. The proper caps will allow venting in both directions.
rfrederick
Posts: 28
Joined: Fri May 22, 2020 8:28 pm
Name: Rick F
Location: 5M3
Aircraft Type: C140
Occupation-Interests: IT
Contact:

Re: One Fuel tank is pressurized

Post by rfrederick »

Got it Blaine.
Thanks again for the info.
Rick
M20C/BC12D/140
8474
Posts: 313
Joined: Sat May 25, 2019 12:08 pm
Name: Blaine F
Location: Saskatchewan
Aircraft Type: C140A
Occupation-Interests: Helicopter Pilot
Contact:

Re: One Fuel tank is pressurized

Post by 8474 »

Rick, you could do as John suggested and remove the silicone valve so it vents in both directions, however the caps you have are quite valuable if you check what the new price is on ACS or even the used prices on eBay. You might be better trying to find the proper caps as depicted in the Neil Wright article and sell those caps. Just a thought.....
rfrederick
Posts: 28
Joined: Fri May 22, 2020 8:28 pm
Name: Rick F
Location: 5M3
Aircraft Type: C140
Occupation-Interests: IT
Contact:

Re: One Fuel tank is pressurized

Post by rfrederick »

Sounds good Blaine.

I am waiting to hear from another C140 owner close to me (next airport north) who might have a set he previously replaced.
Rick
M20C/BC12D/140
User avatar
6643
Posts: 2439
Joined: Tue May 01, 2018 7:00 am
Name: John C
Location: KLCI, NH
Aircraft Type: 1946 C140/C90
Occupation-Interests: A&P, semi-retired
Contact:

Re: One Fuel tank is pressurized

Post by 6643 »

So, you have the earlier system designed for "Both" operation. I agree, the caps with the holes are bullet and idiot proof.
might have a set he previously replaced.
With what? His best bet may to put them back on his plane! ;)
rfrederick
Posts: 28
Joined: Fri May 22, 2020 8:28 pm
Name: Rick F
Location: 5M3
Aircraft Type: C140
Occupation-Interests: IT
Contact:

Re: One Fuel tank is pressurized

Post by rfrederick »

He was not able to find them so I just ordered a set from Aircraft Spruce.

Meanwhile I have lots of time to address years of neglect on this finish...
20200531_164405.jpg
20200531_164405.jpg (289.08 KiB) Viewed 4628 times
Rick
M20C/BC12D/140
8474
Posts: 313
Joined: Sat May 25, 2019 12:08 pm
Name: Blaine F
Location: Saskatchewan
Aircraft Type: C140A
Occupation-Interests: Helicopter Pilot
Contact:

Re: One Fuel tank is pressurized

Post by 8474 »

oh boy Rick, if you think thats years of neglect I would not want to send you pictures of my airplane :D I hope one day to get mine as shiny as yours.
Post Reply