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airlock after fuel drain


johnr

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Happy New year fellow fliers,

I decided that the fuel in the CTsw was getting  old, I have had misfire problems with stale fuel in boat & small motors in the past, Its been very hot for the last month with days in the 40 + ( Celsius) so I decided to drain the fuel through the water trap.

I drained it all & checked the fuel flow on  near empty tanks & found I had about 2.25 L per min which seemed to be quite good.

I put 20L fresh new fuel  in each wing tank & checked for water but there was no fuel in the bowl, ( the tap was fully on).

I tried the starter but of course it would not fire. After about 30 mins I had fuel at the drain but still no start, it was late in the day so I put her back in the hangar.

I  believe that after 30 mins the fuel had not reached the carbs.

The hoses are all in the original position I took photos of them before the rubber change 3 years ago. After the rubber change I had no problems with fuel!.

My  question to the group is the system inclined to get an airlock after a complete fuel drain?

I would hope & expect that when I return it will start . I doubt this could ever happen in flight as the hoses would never be completely emptied of fuel.

John Robert

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Hi John,

 

Nice to hear from you. I'll take your 40C over my 10C.

 

I do lots of wings pulls and hose changes and drain all the fuel. When I put fuel back in the tanks and open the fuel shut-off  and then try a start it kicks over fairly quickly because there should still be some trapped fuel in the fuel hoses, fuel pump and the carb bowls. If you open the gascolator and fuel shut-off you should have almost instant fuel draining. There should be no air locks. It is a straight gravity feed and should have no obstructions.

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I did have one occasion that I remember that the fuel didn't flow on its own. Most of the time it is just like Roger said. I applied a little positive pressure on the tank and it started the fuel moving. The pressure was applied by mouth. Don't even think about using shop air in any way to pressure the tank. I know of a shop that did with a new CTLS and the wound up have to do a major wing repair. I don't remember if the plane I had issues with was a CTSW or CTLS.

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I did a lot a fuel drain on mine ..by the gascolator.

(using regular fuel, ..after 3 weeks,.. I put it in the car )

 

like John, I had air lock,  all the time ,and my solution was to blow in a fuel tank and then the fuel reached the gascolator

 

but in ''down under''   maybe you will have to suck on the gascolator instead :giggle-3307:

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Happy new year to all from Ireland.

A month ago I did exactly the same as johnr. The weather has been unbelievably bad this autumn and winter. Drained the fuel, filled up with 30 litres of fresh fuel and was unable to get it to flow without blowing into the wing tank. Once it was flowing all was well. Did a flow test and recorded about 39 to 40 litres per hour.... Perfect.

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