UPDATE-

OK - I just got back from the Alaska Airman's show and described (with photos) of my one leaking Monarch Fuel Cap. The cap set about 1/3 of an inch higher than the other non-leaking cap and was rattling and blowing fuel out the top. The company sent me a new cap and the same thing no change! Somewhat frustrated, I discussed this now 10+ month problem w/ the rep at the show and he agreed to replace everything no charge and would ship me out a new "complete package" this week. As I was walking away, he suggested I try "one more thing" and showed me an example of a cap that had the cut-out for the chain attachment punched to high in the throat of the assembly therefore not allowing the cap to seat flush and have gasket contact. That made sense to me but seemed like a stretch..... Well, just got home and sure as shit when I pulled the cap off and looked in the throat of the assembly I could clearly see where the cap had been hitting the cut-out for the chain attachment. I removed the chain and in about 30 seconds took a punch and flattened out the cut-out to be flush with the throat and sure as shit- the cap now fits tight and flush. I can now feel the gasket contacting the top. I plan on flying it this week but I am pretty certain this just solved my leaking fuel cap dilemma. It seems too obvious and simple but darn hard to believe I did not see that before. Make no mistake this is a serious QA issue w/ Monarch they need to address but just happy to have the problem fixed for now. I hope this simple fix may help others

Fly Safe - Dave

DBI, thanks for posting that. The ones I got from Bill Barton must have been better quality. Seems like if Hartwig would have done a simple test like Hotrod did it would have saved a lot of grief!!!!!!

DBI- Glad ya figured it out.

I just installed my caps this weekend. I immediately noticed a similar issue right out of the box. When I screwed the cap on I could tell it wasn't on all the way. The chain was blocking the cap from going on all the way. I attributed it to me doing it in my had but I can see if the clasp was out of position or if the chain was balled up on once side it could be an issue.
I love the caps and they are a huge improvement from what I had.
I'm not sure if the chain is going to be an issue or if I should just remove it.



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Thanks for posting this Dave. Sounds like a possible solution - I'll have to check my caps. Was getting ready to throw them all in the trash.

So much for all the 'you must have installed them wrong' replies.... Sounds like they must have had a batch just a little off on dimensions leading to a lot of tail chasing for us. I'll post back if it fixes my 3 sets of leaky caps.

UPDATE-

OK - I just got back from the Alaska Airman's show and described (with photos) of my one leaking Monarch Fuel Cap. The cap set about 1/3 of an inch higher than the other non-leaking cap and was rattling and blowing fuel out the top. The company sent me a new cap and the same thing no change! Somewhat frustrated, I discussed this now 10+ month problem w/ the rep at the show and he agreed to replace everything no charge and would ship me out a new "complete package" this week. As I was walking away, he suggested I try "one more thing" and showed me an example of a cap that had the cut-out for the chain attachment punched to high in the throat of the assembly therefore not allowing the cap to seat flush and have gasket contact. That made sense to me but seemed like a stretch..... Well, just got home and sure as shit when I pulled the cap off and looked in the throat of the assembly I could clearly see where the cap had been hitting the cut-out for the chain attachment. I removed the chain and in about 30 seconds took a punch and flattened out the cut-out to be flush with the throat and sure as shit- the cap now fits tight and flush. I can now feel the gasket contacting the top. I plan on flying it this week but I am pretty certain this just solved my leaking fuel cap dilemma. It seems too obvious and simple but darn hard to believe I did not see that before. Make no mistake this is a serious QA issue w/ Monarch they need to address but just happy to have the problem fixed for now. I hope this simple fix may help others

Fly Safe - Dave

Flight Check - Just got back from Moose Creek and happy to report for the first time since I have installed my Monarch Caps the right one no longer leaks!! This is a ridiculously simple solution to a problem that has been haunting me for a year +. Monarch obviously had a QA issue w/ some of there caps. Just glad the f$cking thing does not leak anymore!!

BTW- Moose Creek is awesome already! Be Safe - Dave

So I am going to be the "bad guy" here but this is exactly the type of thing that AD's are for. This problem and what was found should be reported to the FAA office that supervises the STC as it is apparent that the manufacturer does not want to address it or there would be a service bulletin. This is definitely a safety of flight issue and someone could be injured or killed. Discussions of problems like this on internet forums still leave many at risk. Stepping down off my soap box now.

Tim A&P IA

bat443 wrote:So I am going to be the "bad guy" here but this is exactly the type of thing that AD's are for. This problem and what was found should be reported to the FAA office that supervises the STC as it is apparent that the manufacturer does not want to address it or there would be a service bulletin. This is definitely a safety of flight issue and someone could be injured or killed. Discussions of problems like this on internet forums still leave many at risk. Stepping down off my soap box now.

Tim A&P IA

I agree but...
I don't think your the bad guy at all.
Some companies identify problems or its brought to their attention. They can issue service bulletins, service letters, or notify all invoiced customers of the possible effected lots. There sure are allot of possibilities a company can take to notify customers of a possible issue. They obviously admitted they knew of this "possible" issue to one guy. Seems pretty easy to notify customers, some how, of a simple measurement of the chain tab for interference. An AD wouldn't be out of line considering no other notifications have taken place and even previous calls to the company didn't yield any useful info from customers.

Update...
So far so good. I have a long X country coming up. This will be a good test. Manarch sent me new caps. The "clutch" is set tighter on these. They will get tighter. I am sure hoping that this is behind me. If the weather lets me out this weekend I am taking my plane to Stene Aviation for some wing mods.
John

Awesome! I hope it fixes it for you. I like simple fixes. It seems like I read that same thing on another BCP thread.

So, after no issues with my new plane's Monarchs, I had something interesting happen today. Last week I noticed some stains after of my right Monarch cap. So I cleaned the brownish stains so I could check it. It was obvious something had ran down the wing from the cap. No blue dye. So, I flew for a few hours and it was fine. Then I refueled and flew home. When I got there, there was blue dye all over the top of my wing. When I fuel, I usually bring it up halfway into the cup above the flapper valve. I don't know if this is correct or not for the Monarchs...I've never read one way or another. I've fueled my previous plane this way and this one for a total of 4 years with no problem. But now this one side seems to be siphoning out. Any thoughts? I'm guessing it is just the amount in the cup because my fuel burns are still right on with my JPI. So if this is the case, do I just not fill into the cup? Or do I flip the gasket? (Another Monarch thread someone posted about them siphoning and that flipping the gasket fixed it.) Or get a new gasket?

Thanks!

I spoke to Monarch this morning and here's a few things he told me that I thought I'd pass on.

1- They recommend replacing the gasket every 4-5 years.
2- You can extend the life of them by annually taking them off and rubbing them with mineral oil.
3- You can flip the o-ring to get some more life out of it, but you will loose some of the water protection.
4- A new pair of slotted o-rings from them run $45. He says they are the only ones that make them, (part # GAR 0998).

I had to get off the phone so I couldn't drill down on this like I wanted. In the installation manual for the cap, it lists the o-ring seal part number as MS29513-140, which is just a regular o-ring. Definitely not the slotted o-ring that is on there. So did they originally use the -140 and later switch to the slotted? And, can you use either, or is the new slotted o-ring mandated?

Here's a pic of mine----notice the under side of the umbrella is different than your's. Mine are from around 1990 or so and have the original U shaped gasket---don't think round was ever supposed to be used but who knows.

Hmmm...interesting. That is very different.


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OK, I will say I am good. I should post photos of the trip. What a great time of year it was!! But this is about the caps.. I left Saturday afternoon at 4 PM from my strip in Louisiana. (not as early as I wanted) Flew 4 hours to Sublette, KS. No Leaks>>>>> Back in the air at 7 am on Sunday. Two stops later I was in Polson, MT.. 11.2 hours and NO leaks at all the whole way..... I left the plane with Willie Stene for some SWEET Mods... I cant wait to get her back...

John

Glad to hear...and that is exciting about the mods!


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So, I got back into town today and went and got some of the O-rings listed on the installation instructions. Once I pulled the one off the cap, it was obvious they weren't even close. Which confuses me.

So, if you ever need to replace them, account for the lag time to get them from Monarch and to pay a premium. I'm going to flip it and see how that goes.

Here are some pics of their slotted o-ring and the one listed on their part number.





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I never turned mine yet and have noticed they still have a squeaky sound of the gasket snugging before the clicker kicks in.

I went out and flew yesterday to warm the oil up to change it. This was the first flight after flipping the o-ring. Back at the hangar, I couldn't see any hint of leaking. So for now I think the issue is put to bed.


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Good deal!

At Sun-N-Fun I went by the Monarch booth. They gave me a free pair of the o-rings. Something to keep in mind if anyone is going to KOSH.
John

Sounds like the Monarch problem is solved.

https://backcountrypilot.org/forum/fs-m ... caps-20589