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Fuel cap needed


rotorman

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Believe it or not these two fuel necks are from my airplane. The one on the left is the one that needs a cap that I lost. The neck on the second one takes a Shaw 531-001 of which I now have two. I made the ridiculous assumption that the caps and necks are the same on both sides, so I ordered another 531-001 cap to replace missing one. You can imagine my surprise when I found they are not the same. I have owned this airplane for more than 20 years and never noticed the difference.  

The one on the top has any 90 mm ID on the upper ring and a 75 mm ID on the lower ring. The second one has the same upper ID but it has a second lip and a narrower lower ID. The three slots are also different sizes. If anyone recognizes the upper one as the one on their airplane could you remove the cap and pass along the information found on the bottom? As a reference I included a pic of one of the caps I have for second  fill neck. The part number is partially obscured by the tab but it's a 531-001 and definitely do not that one I need. 

20210417_100724.jpg

20210417_100753_LI.jpg

20210412_123815.jpg

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59 minutes ago, M20Doc said:

Do you think the narrow neck has the Shaw restrictor and the wide neck does not? That would beg the question of why would someone do that? Who knows, right?

I can't find a source for that kit. Any ideas? 

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11 hours ago, rotorman said:

Do you think the narrow neck has the Shaw restrictor and the wide neck does not? That would beg the question of why would someone do that? Who knows, right?

I can't find a source for that kit. Any ideas? 

I would say that one has the restrictor and one is standard.  Let me look through my collection and see what I have.

Clarence

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Thanks for all the help.

This is getting a bit confusing. I have two of the caps that look the same as in your photo (see my previous post). Two of your caps are 531-046. My two caps are 531-001. On my airplane the -001 caps fits the neck with the restrictor. So I think I should add the restrictor to the neck that has the missing cap since I have two of the 001 caps. The Service Bulletin you included in a previous post calls out the 531-001 in the parts list that comes with the restrictor kit. The IPC also calls out -001 with the restrictor.

A concern I have is how I lost this cap since during prefight I checked the fuel level and locked down the cap. I think the restrictor is a compression fit. Is it possible I lost the cap along with the restrictor? The Service bulletin calls out a special tool to twist the restrictor into the locked position. There must be some tabs on the underside of the restrictor that engage to hold it in place. Is that correct?

Again, I appreciate the help.

Nick 

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2 hours ago, M20Doc said:

The tool has 3 legs to engage the ID of the restrictor.  You then press the tabs down to lock it in place.

Clarence

I would like to purchase the restrictor and tool if you have it. Can I send you a private message to exchange information?

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Follow up for @rotorman...

 

I’m going to guess... somebody changed out one of the fuel necks...

The one that got left in place... doesn’t have the same shine as the newer one...

The one that has no shine to it... is probably not stainless steel.

If you get a pic from inside the tank.... looking up at the fuel neck... you might see a bunch of rust back there...

 

This is experience form a 1965 M20C... eventually the fuel neck rusts through from the inside out... and rain water then gets into the tank...

Swapping out the fuel necks, if needed, isn’t too difficult... but does require sealant and rivets... so it’s not really easy either...

On a second look at the shiny fuel neck... it looks like it has original paint on it as well...(?)

PP thoughts only, not a mechanic...

Best regards,

-a-

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The missing restrictor has been installed thanks to Clarence. The missing cap I found used at Bas Aircraft Parts.  I got the O ring kit for the cap from Gallagher.

I am now certain that the cap and restrictor came off together during flight. Here is what to look for if you don't want this to happen. Embossed on the restrictor are the words "This end up". When standing in front of the wing those words should be oriented so you can read them right side up, left to right. This orientation also allows the cap lock tab to lay straight back in the locked position, not cocked left or right. On my airplane both caps were cocked left about 30 degrees. The picture below is how the cap slots should be oriented when looking into the tank.

Part numbers: fuel cap Shaw 531-001. Restrictor Shaw 557-003 

 

 

 

restricter.PNG

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Was it only glued in place?

Even then... the man hole theory applies...   the manhole is slightly larger than the hole it covers... so it can’t fall in... no matter what the orientation is...

In this case, it is on the other side of the wing’s sheet metal hole... it can’t fall out...

I assumed these rings are riveted in place...

Check to see it didn’t fall into the tank...  :)

PP thoughts only,

-a-

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11 hours ago, rotorman said:

The missing restrictor has been installed thanks to Clarence. The missing cap I found used at Bas Aircraft Parts.  I got the O ring kit for the cap from Gallagher.

I am now certain that the cap and restrictor came off together during flight. Here is what to look for if you don't want this to happen. Embossed on the restrictor are the words "This end up". When standing in front of the wing those words should be oriented so you can read them right side up, left to right. This orientation also allows the cap lock tab to lay straight back in the locked position, not cocked left or right. On my airplane both caps were cocked left about 30 degrees. The picture below is how the cap slots should be oriented when looking into the tank.

Part numbers: fuel cap Shaw 531-001. Restrictor Shaw 557-003 

 

 

 

restricter.PNG

 FedEx screwed up the delivery, glad they got it sorted out.  Be sure to press the 3 lock tabs down so it can back out.

Clarence

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14 hours ago, carusoam said:

Was it only glued in place?

Even then... the man hole theory applies...   the manhole is slightly larger than the hole it covers... so it can’t fall in... no matter what the orientation is...

In this case, it is on the other side of the wing’s sheet metal hole... it can’t fall out...

I assumed these rings are riveted in place...

Check to see it didn’t fall into the tank...  :)

PP thoughts only,

-a-

I can't fall into the tank since it is larger than the fill neck, but it can come out with the cap if installed incorrectly. 

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8 hours ago, M20Doc said:

 FedEx screwed up the delivery, glad they got it sorted out.  Be sure to press the 3 lock tabs down so it can back out.

Clarence

Yeah. It was 6 days on a 2 day delivery. I almost gave up.

I did not know there were lock tabs. I saw the tabs on the underside. So are you saying I press down on the three indents that the arrows are pointing to? Do I just use a screwdriver to press them down. The SB said to turn the restrictor with the tool it until I hear a click. That did not happen after I rotated it about 20 degrees with the cap on.  I rotated the one in my other tank also so that it lined up correctly but no clicking sound there either.  I thought it strange that they were designed without a lock.   

Capture.PNG

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On 4/28/2021 at 3:32 PM, M20Doc said:

I would press the 3 tabs down a little to make sure that the ring and cap can’t turn loose.

Clarence

The tabs can be bent down prior to installation as you point out. It adds some for friction but the restrictor/cap assembly can still be rotated by hand after the lock tab is pulled up.  The installer of my restrictors did not do that step, and I did not pay attention to the fact that the cap was slowly rotating over time and working its way to coming off. Therefore, I added a new preflight item. Fuel cap lock tabs full down and pointing aft.

S50, the airport from which I fly about 1/2 the time, found my cap with the restrictor attached on the runway. So now I have a spare one of each.

 

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Just now, rotorman said:

The tabs can be bent down prior to installation as you point out. It adds some for friction but the restrictor/cap assembly can still be rotated by hand after the lock tab is pulled up.  The installer of my restrictors did not do that step, and I did not pay attention to the fact that the cap was slowly rotating over time and working its way to coming off. Therefore, I added a new preflight item. Fuel cap lock tabs full down and pointing aft.

S50, the airport from which I fly about 1/2 the time, found my cap with the restrictor attached on the runway. So now I have a spare one of each.

 

Nice to know where it ended up.

Clarence

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