Fuel Tank Filler

[170C]

One of our 170 members who doesn't normally do posts on our forum asked me to make an inquiry for him. He is having to replace his right hand fuel tank (I earlier posted to see if anyone had one for sale) and he has purchased a C-140A Patroller fuel tank. That tank is the same 21 gallon one as we have in 170's & early 172's. He is having an issue with the fuel cap clocking. One way the fuel cap is off center one way and the other way its off also. What I am trying to describe is the ears/tabs (?) on the cap doesn't line up with the fugelage. Is there a means of changing the orientation of some of the adapter ring, etc. to get the correct clocking position? I know when I pulled my two fuel tanks to replace the gaskets at the filler location, I got one back properly and one isn't clocked correctly. I just live with it!

Also, as I recall, the spout itself is screwed into the adapter and the threads have been staked to prevent its unscrewing from the adapter. What would be needed to unstake that spout and turn it for proper clocking and restake the threads. Suggestions appreciated.

[hilltop170]

Frank
My right fuel tank cap is about 45° off. The left is inline with the airplane centerline. This doesn’t help but that’s the way mine is.

[jlwild]

One of our 170 members who doesn't normally do posts on our forum asked me to make an inquiry for him. He is having to replace his right hand fuel tank (I earlier posted to see if anyone had one for sale) and he has purchased a C-140A Patroller fuel tank. That tank is the same 21 gallon one as we have in 170's & early 172's. He is having an issue with the fuel cap clocking. One way the fuel cap is off center one way and the other way its off also. What I am trying to describe is the ears/tabs (?) on the cap doesn't line up with the fugelage. Is there a means of changing the orientation of some of the adapter ring, etc. to get the correct clocking position? I know when I pulled my two fuel tanks to replace the gaskets at the filler location, I got one back properly and one isn't clocked correctly. I just live with it!

Also, as I recall, the spout itself is screwed into the adapter and the threads have been staked to prevent its unscrewing from the adapter. What would be needed to unstake that spout and turn it for proper clocking and restake the threads. Suggestions appreciated.

Frank and Richard, clocking can be corrected on 55 B Model tanks. See pictures in MX Library, Fuselage,Wings, and Tail Section, titled “Fuel tank removal (55 B Model)”.

After I replaced both filler neck tank gaskets I miss clocked one tank. So, I readjusted by dropping filler neck down into tank and rotating 45 degrees. Secondly, a C-140A Patroller tank filler tank “could be different” than late model 170B’s and early 172’s.

[170C]

Richard my tank are oriented the same way as yours. I’ve thought about doing what Jim said since mine were correct prior to my removal of my tanks. I looked at the 140-A tank Saturday and the removed tank and they appear to
Be exactly the same.
Any idea on the staking question?

[hilltop170]

Frank
I would not mess with the staked neck. You could cause more problems than you might fix.

I don't think straightening out that gas cap will change your plane's nickname.

[c170b53]

Staking appears to me to be overkill and I agree with Richards assessment. Sorry Frank , may be you could just paint the caps RED to make-up your speed loss.

[DaveF]

The filler neck is attached with six screws so it can be rotated in 60 degree increments. I’ll try to find a picture that shows this. Edit: Looks like Jim W already described it. Remove the six screws, rotate to the next position, apply sealant, and replace the screws.

[170C]

I appreciate the suggestions. I'll pass this info onto our 170 member in Lebanon, TN.
Fortunately this isn't for Ole Pokey. My fuel caps are already red. Probably why its Pokey Might paint them GREEN, as that might add some speed and offset the drag resulting from my one cap that is also not clocked properly

[GAHorn]

Red fuel caps don't create the drag that Green ones do … so don't spend a lot of effort risking damage to the filler neck trying to align them.

Seriously, I have an undocumented opinion I'll express on this subject: The original fuel caps did not have the "ears" which disturb us. They were "flat" type caps.
When vented caps were developed Cessna came up with the updated design (w/ears) which also make preflight easier to determine if the caps were installed completely before flight (since the filler is in a low-pressure area which will siphon fuel from an un-capped tank.)

The method to align the ears is to over-ride the staked filler neck and twist the neck to a position on the flange (which others mentioned can be "clocked") that makes the alignment. The problem with doing that "in situ" is the risk of damaging the threads ...and the problem of re-sealing the threaded area from fuel and water/rain leaks. (Using a Pro-Seal type product is the usual manner when assembling the necks to the tanks.)

I have forgotten the details of how I did it, but my C-206 suffered from mis-aligned fuel cap ears and I disassembled the caps and discovered I could re-assemble them such that the ears were aligned with the slip-stream. Sorry not to have pics of that, nor do I have any approval basis, and I've slept since I did that (and sold the airplane so it's no longer my problem.)

My 172C has mis-aligned ears and I don't care. I pretend they are like "mini-VG's" and therefore make up for any drag.

[rmorton]

I'm trying to remedy the same problem here. One of my caps is 90 degrees off when tight. Not only does it drive me crazy to look at it, I have a friend (with similar misaligned cap) who nearly missed the fact that the line crew didn't tighten his cap after refueling. They oriented it straight with the fuselage but it was barely "hooked". That becomes a safety issue (yes, it should be addressed in pre-flight but would be nice to eliminate that potential altogether.) It seems there should a solution to this.

Since the neck is attached to the tank with 6 screws, we can only adjust in 60 degree increments. So getting to 90 degrees by turning the whole assembly isn't going to work. We have it taken down to the same level as Jim Wildharbor shows in his powerpoint. I can't see how the neck is "staked" to the piece in the tank, but the threads appear to be very well sealed.

Any other thoughts or ideas besides just accepting it as is?

Oh, and one other interesting discovery - the inner tank gasket was altogether missing on this tank! I can see where that could get overlooked when referencing the IPC because it doesn't show the inner gasket in the diagram.

[c170b53]

03EDF413-0EE7-43C8-B5E9-0A8A759BA6EF.jpeg (37.74 KiB) Viewed 1111 times

If its not staked on the inside, you’re in luck, the neck is threaded into the flange that sits in the tank and a tool such as this one might get it moving

F7D8F067-F14E-4657-B43C-F3F5752D6044.jpeg (30.11 KiB) Viewed 1111 times

and closer

0646B2C1-4F9C-434D-B5C7-5F571180F329.jpeg (34.69 KiB) Viewed 1111 times

[c170b53]

Then again if it doesn’t easily budge, if its not really broken, it will be.

[DaveF]

No way I’d use a tool like that with the flange still attached to the tank. If you had things taken apart for tank re-sealing, you’d be able to apply solvents and heat, then the wrench, without damaging the tank.

[ghostflyer]

I may be wrong about this ,but some where in the back of my brain is telling me you can adjust the cap pawls to suit . However be very careful of that red button flap[valve] as they can break easily and getting parts are very hard . Basically you are pulling the cap apart . I haven’t any caps at home but will look when I go to the hangar Tuesday . There is an Allen screw on top of the cap that’s screwed all the way out .

[GAHorn]

I may be wrong about this ,but some where in the back of my brain is telling me you can adjust the cap pawls to suit . However be very careful of that red button flap[valve] as they can break easily and getting parts are very hard . Basically you are pulling the cap apart . I haven’t any caps at home but will look when I go to the hangar Tuesday . There is an Allen screw on top of the cap that’s screwed all the way out .

Those little rubber “flappers”…are also used in Holley carburetors. They are called “umbrella check valves” and replacements can be found online, Holley PN A49X2. I hesitate to post this link because I’m camping in a state park with public wifi and the pics aren’t showing up…but hopefully this is helpful: https://www.ebay.com/sch/i.html?_id=124 ... PACK+A49x2