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OS 46 AX fuel feed problems

Old 03-19-2010, 01:04 PM
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Default OS 46 AX fuel feed problems

I have an OS 46 AX mounted in Seagull Models Decathlon using all of the stock items fuel tank, engine mountm, ect. I have checked the entire fuel system for leaks and obstructions and can find nothing. I have even replaced the o=ring under the carb and still cannot pull fuel from the tank. I am using a Dubro fueler and have even bipassed it thinking that it could be the problem and still no fuel feed. About all that I haven't done is replace the backplate gasket.

Any ideas out there?

Old 03-19-2010, 10:03 PM
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Default RE: OS 46 AX fuel feed problems

Sounds like you have checked just about everything... what about the clunk and the fuel line in the tank?
dan
Old 03-19-2010, 11:43 PM
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Default RE: OS 46 AX fuel feed problems

I have had the tank out an apart at least three times to check for leaks under water and to check to make sure that the clunk is working free. I have also checked the infeed and pressure lines as well. I have been doing this for a long time and this is becoming a very baffling situation.

Thanks for checking out my plight.

Jack
Old 03-22-2010, 09:03 AM
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Default RE: OS 46 AX fuel feed problems

If the engine will not draw fuel, but you have good compression, then the problem just has to be in the fuel system.

If you remove the engine from the model and put it on a test fixture with everything out in the open, you can then see if you actually have an engine problem.

Here are the things that will prevent fuel draw:

Bad piston/cylinder fit
Bad crankcase-rear cover fit
Blocked fuel passages in carburetor
Holed fuel lines
Obstructed fuel lines
Fuel lines not actually in the fuel (this is VERY commoncheck to see if you're trying to draw fuel from the vent, or if the clunk is out of position)
Pinched fuel lines
No fuel in tank (yep, I've seen this, too!)

And so on. Most of the time, the problem is not in the engine, itself, but elsewhere. Using a test stand will be a great help.
Old 03-22-2010, 12:30 PM
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Default RE: OS 46 AX fuel feed problems

Thanks for your reply. I have done just about all of the things that you suggest. Upon examining the set up again it appears that the stock set up places the fuel tank very low in comparison to the engine (something that I should have seen before) so I will be raising the tank today. I probably didn't think to check this item closely earlier because the tank mount is built into the laser cut fuselage frames. Of course, I'll have to cut those away to raise the tank about an inch or more if possible.

Thanks again for your advice. I'll let you know how raising the tank works out or the other suggestions if they prove necessary.

Jack
Old 03-23-2010, 11:16 AM
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Default RE: OS 46 AX fuel feed problems

I cut away the fuselage former last night and was able to raise the tank 1 to 1 1/2 inches and the problem is gone. Thanks for your advice.

Jack

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