M20E fuel cap - fix?

[lithium366]

When I am closing my left fuel cap - the lever doesn't feel tight and returns to a partially open (up) position. During the last annual 2 weeks ago o-rings were replaced. I wonder if someone experienced a similar issue and (hopefully) fix is trivial

[MB65E]

The nut might just be too tight. You’ll need new cotter pins. 

-Matt

[lithium366]

38 minutes ago, MB65E said:

The nut might just be too tight. You’ll need new cotter pins. 

-Matt

Thanks, will try tonight! Are these cotter pins should be for aircraft or any from Home Depot or automotive store will work?

[Vance Harral]

13 minutes ago, lithium366 said:

Are these cotter pins should be for aircraft or any from Home Depot or automotive store will work?

You want the cotter pins with the specific part number called out in the M20E parts manual.  You can order them from Aircraft Spruce, or other online aircraft parts suppliers.

While these are "probably" the same cotter pins as the ones in my M20F, I'll let an M20E owner chime in to be sure.  If you don't have a parts manual, you'll want to obtain one from Mooney.

[Guest]

3 hours ago, lithium366 said:

When I am closing my left fuel cap - the lever doesn't feel tight and returns to a partially open (up) position. During the last annual 2 weeks ago o-rings were replaced. I wonder if someone experienced a similar issue and (hopefully) fix is trivial

Service bulletin M20-229A should be your guide to fuel caps.

https://cdn2.hubspot.net/hubfs/4147179/technical_documents/service_bulletins/sbm20-229a.pdf

Clarence

[lithium366]

2 hours ago, Vance Harral said:

You want the cotter pins with the specific part number called out in the M20E parts manual.  You can order them from Aircraft Spruce, or other online aircraft parts suppliers.

While these are "probably" the same cotter pins as the ones in my M20F, I'll let an M20E owner chime in to be sure.  If you don't have a parts manual, you'll want to obtain one from Mooney.

In the manual it only comes as an assembly part so I could probably buy o-rings from SB posted above and it comes with a cotter pin

[Yetti]

If you go Fluorosilicone they should last more than a year.

https://www.amazon.com/Fluorosilicone-Ring-Durometer-Round-Blue/dp/B003SLE5KY

for the F for the shaw caps 010 are the inners and 338 are the big ones.  Unless you have bladders    Need 4-010 and 2-338

 

[Vance Harral]

55 minutes ago, lithium366 said:

In the manual it only comes as an assembly part.

Apologies for the confusion.  I coulda sworn the individual parts were broken out including the cotter pin.  But when I looked in my parts manual I found the same thing as you: only the O-rings are broken out, the rest of the cap is only referred to as an assembly.

The critical point is, you want aircraft-grade, cadmium-plated cotter pins, like these: https://www.aircraftspruce.com/catalog/hapages/cotterpins2.php.  If you just go to the local hardware store, you're likely to wind up with mild steel cotter pins with no plating or other corrosion protection.  These are much more likely to rust, and consequently fail and/or drop contaminants into the tank.

I bought an assortment of cad-plated cotter pins from Spruce a while back, put them in a fishing tackle box along with other miscellaneous hardware, and use a few at every annual: fuel tank caps, seat rail pins, etc.

[carusoam]

As trivial as fuel caps seam...

1) losing one is expensive...

2) too loose, water gets in...

3) too tight, cam wear becomes a challenge for the cap.

4) There is a guy... that shares many details with his cap knowledge...

PP thoughts only, annual annoyance caused by inspection of fuel cap seals... 

Best regards,

-a-

[Prior owner]

18 hours ago, M20Doc said:

Service bulletin M20-229A should be your guide to fuel caps.

https://cdn2.hubspot.net/hubfs/4147179/technical_documents/service_bulletins/sbm20-229a.pdf

Clarence

Hey Doc- 

I’ve had my caps apart and never saw the half moon shaped piece that is depicted in the SB drawing (directly underneath item #2).  It is not identified by number, either... am I missing this part?

 

[Guest]

1 hour ago, PilotCoyote said:

Hey Doc- 

I’ve had my caps apart and never saw the half moon shaped piece that is depicted in the SB drawing (directly underneath item #2).  It is not identified by number, either... am I missing this part?

 

As far as I know they all have the crescent shaped stainless steel washer, there is usually as shallow counter bore for is to  sit in.

Cl;arence

[Prior owner]

10 minutes ago, M20Doc said:

As far as I know they all have the crescent shaped stainless steel washer, there is usually as shallow counter bore for is to  sit in.

Cl;arence

Thanks. I’ll have to look again- perhaps they are just stuck in there (I didn’t see a counter bore).

[MarkC]

I have had a little experience with this situation too.  Once you have addressed the O rings and cotter pins as others have posted above, I have another item to check if you still have the issue.  My cap levers did not want to "snap" down and firmly close either.  They actually wanted to stand up a little from the down and closed position.  I disassembled the caps and noticed that the flat surface on the bottom of the lever no longer had a sharp 90 degree corner at the edge where it rotates up.  I used a belt sander and sanded the flat bottom of the lever to return it much closer to a sharp 90 degree turn at the edge.  Over time, the open and closing operation of the lever had worked that sharp turn down on my fuel cap levers. Now the snap closed rather smartly and stay there.

 

Mark

 

[Vance Harral]

1 hour ago, PilotCoyote said:

Thanks. I’ll have to look again- perhaps they are just stuck in there (I didn’t see a counter bore).

More likely they were lost by someone who disassembled the caps to install new O-rings in the inner shafts.  The first set of caps on our airplane were missing these washers too.  They "worked", but one side was pretty wonky - I think in part because without the sacrificial washer, the cam-shaped corner of the lever wears against the bulk of the cap.  We bought some second-hand units which had the washers and they work better.

[Prior owner]

Had a chance to look at my caps today- the half moon washers were right where they are supposed to be.... they are probably stuck in there, as I had the caps apart when I cleaned and painted them, and I had no idea that they were a separate piece. Glad they aren’t missing!

Edited June 29, 2019 by PilotCoyote

[lithium366]

What I discovered is that my cap is tightened all the way to the point where nut can't longer move. If I loose it a bit - an entire cap became loose so I assume it is my time to replace the cap unless I can buy a spring separately

[Igor_U]

3 hours ago, lithium366 said:

What I discovered is that my cap is tightened all the way to the point where nut can't longer move. If I loose it a bit - an entire cap became loose so I assume it is my time to replace the cap unless I can buy a spring separately

It is not the spring.

I believe your cap levers don’t “snap” when closed as they are worn and rounded. See the fix described in one of the previous posts.

I had the same issue years ago so my memory is fussy.

I think, a thin SST washer under could help but then there are half-moon washers there anyway..

[carusoam]

Check In with @OSUAV8TER for additional ideas... rehab old caps or swap with new...

Best regards,

-a-

[OSUAV8TER]

I have  some used Shaw 431-9 and 431-9R fuel caps on hand if anyone needs them. Gallagheraviationllc@gmail.com

James