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  #1  
Unread 06-06-19, 12:26 AM
wslade2 wslade2 is offline
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water in fuel

have had plane away from home and hanger, so tied down outside. Some rain storms came through. Found quite a bit of water in tanks when sumping them. Open fuel doors and there is standing water in the bowl where cap is. I notice a small opening in the rear of bowl. I interpret this as a drain for collected water in the bowl. But it is not allowing water to drain out. I tried running a wire through it and got 5 inches down but still water will not drain. I put a piece of rubber tubing up to the opening and tried blowing though it but air will not pass. Am curious of the construction on back side I can not see. Is there a tube hooked up? Metal? Rubber? Is that what is blocked? I am thinking of using a compressor and trying to blow 100 psi though it but would prefer to know what is on back side before doing that. No details are given in parts or service manual. To access back side of bowl looks like would have to support wing and remove upper wing panels over fuel tanks. water pooling in the bowl where gas cap is, getting past gasket and into tank potentially dangerous. Probably removed up to about 1/2 cup of water from just one of the tanks. Any experiences with this appreciated.
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Unread 06-07-19, 05:40 PM
GAdams GAdams is offline
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There is a small metal tube on the under side of the wing and the tail boom pylon for the respective fuel bowels. Buy a package of old fashion pipe cleaners and work your way down from the top and up from the bottom side to clear the debris. 100 PSI of air is too much. You could try a gentle stream of air. Use the same cleaners to open the holes on the bottom of the rudder fairings. Likely they are plugged too.
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Unread 06-08-19, 05:21 PM
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hharney hharney is offline
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What year is your plane? It is best to know this when you post so that other can provide the correct information to help you. Have you talked to a mechanic A/P? Might be best to get some advice on this as moving forward with extreme ideas can cause more issues that may be unknown. Please be careful and get the certified help.
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Unread 06-13-19, 11:47 PM
wslade2 wslade2 is offline
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We have had rain after rain here. The water collection occurred while tied down at shop for service by A and P (they're tight on space and move planes in and out-I go and physically check every couple days when outside).
My 337 is a 1970 E model. I have the standard cessna style cap that uses a 1/8 to 1/4 turn to lock. I found a drawing of the drain for the inboard tanks. It is called a scupper drain. For the inboard tanks, a metal tube heads aft and outboard until hitting a bulkhead/rib. It joins an AN fitting. Continuing on the other side after the AN fitting is a rubber tube. The rubber tube then joins another AN fitting that is in the "roof" of the compartment where header tank is at base of boom joining wing. Removed the access panel for the header tank and there is a short s-curved extension to the outside/bottom of access panel/boom. I found it easier to to remove this s-tube in order to clean the drain. Pipe cleaner good idea. I got larger longer fluffier ones from Hobby Lobby. At first the pipe cleaner would not go through. Some layered dirt had hardened in AN fitting which is an area of narrowing. Used some stiff steel wire with a 30 degree 1/16 length bend/hook on the end of it to catch/pull/dig on dirt. Took many manipulations to break it up. Put a small amount of water in scupper so I could tell when there was flow. Once dripping, ran the pipe cleaner through several times and flushed with water carefully. The outboard tanks scupper drain is a straighter shot and less trouble to clean. no s-curves. All were blocked. There are two drain tubes under each wing for scupper drains: 1 inboard and one outboard tank. Don't confuse with drain for boost pump which comes out through rectangular access panel near leading edge of wing (which makes for a 3rd tube poking out the wing bottom).
I replaced the gaskets on the caps. I could tell this helped alot as when one of the rains passed through, water was pooling in the scupper drain and not getting past gasket into tank. The old rubber gaskets "looked" ok but when manipulated showed cracking and brittleness. I would have a low threshold for replacing these. Cheap insurance.
Thanks!

Last edited by wslade2 : 06-14-19 at 12:08 AM.
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Unread 06-13-19, 11:59 PM
wslade2 wslade2 is offline
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I read Herb Harney's post of 6/12 with great interest and plan on conducting said test:
********************************************
"Let me discuss one issue that some folks have had that the new caps will not fix. In the service port of our aircraft is an overflow tube that collects small amounts of overflow and allows the fuel to exit under the wing. These small tubes are also suppose to drain any water that may try to collect in this service port when the aircraft is stored in the elements. Everyone should test these drains to be sure they are not broken or cracked. If they are compromised you will not know unless you try this test. Take a small amount of fuel and pour it into the service port, with the fuel cap on, while the bottom of the tube under the wing is plugged. Either have someone pour the fuel while you hold your finger under the tube under the wing or plug the tube with something that will not harm the pipe. If the fuel pools in the service port then the tube is sealed and working correctly. If the fuel drains from the service port then there is a crack or the tube is broken inside the tank. This is how the water intrudes into the fuel cell. I have personally seen this on my airplane and have read from others that this has happened. In fact it was determined that the Skymaster departing Point Lookout in Branson, MO had this very issue. Check your tank drains folks and if you have a problem be very careful when you leave your aircraft in the elements."
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Also was not aware there is a Monarch fuel cap modification
The earlier part of the thread also discusses the maneuver to be sure tanks are empty of all water and plan on doing that before next flight.

Last edited by wslade2 : 06-14-19 at 12:06 AM.
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  #6  
Unread 06-16-19, 11:34 AM
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hharney hharney is offline
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Quote:
Originally Posted by wslade2 View Post
Also was not aware there is a Monarch fuel cap modification
The earlier part of the thread also discusses the maneuver to be sure tanks are empty of all water and plan on doing that before next flight.
Wade, I am not aware of any Monarch fuel cap mod for us. The new caps are what you have now from your description above. The old caps are the plunger type with the flip lock on the top. Sounds like you have the latest and greatest already
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