O.S. GF40 carb not drawing fuel - RC Groups
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Nov 09, 2017, 06:34 PM
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mosquitowings's Avatar
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O.S. GF40 carb not drawing fuel


Hey guys and gurus! I have an O.S. GF40 that has stopped drawing fuel. I have gone through the carb and checked everything I can and no luck.
The diaphragm seems to be ok, the needle mechanism seems to be working, it just won't pump! I know the engine will run because it will start with a prime and run for maybe 3-4 seconds 'till it runs the prime out, it just won't pull the fuel through to the carb. And yes, the tank, lines and fuel are in good working order.
SO.........any ideas? I'm about to pull my hair out
Thanks, Jim
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Nov 09, 2017, 10:41 PM
AMA 46133
Quote:
Originally Posted by mosquitowings
Hey guys and gurus! I have an O.S. GF40 that has stopped drawing fuel. I have gone through the carb and checked everything I can and no luck.
The diaphragm seems to be ok, the needle mechanism seems to be working, it just won't pump! I know the engine will run because it will start with a prime and run for maybe 3-4 seconds 'till it runs the prime out, it just won't pull the fuel through to the carb. And yes, the tank, lines and fuel are in good working order.
SO.........any ideas? I'm about to pull my hair out
Thanks, Jim
Most likely something going on with the pump. Have you checked the hole on the back plate where the crank case pulse tube is connected to? Maybe the hole is clogged with oil. How about the short Tygon tube connecting the carburetor to the crank case vent? Is the tube seated and sealed.

Have you remove the back plate and check those passages?
Nov 10, 2017, 12:06 AM
Registered User
Sounds like some debris has gone through the carb. Take the carb apart again, and back flush every port, try shaking the carb housing while back flushing, because there is a "disk blanking plug" that has a check ball under it, they are a real pain to remove, and you need a new disk that needs special attention when installing, so don't remove the disk unless you know what you are doing. Also check the PCV valve in the back plate.


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