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2018/05/28 18:39:52
sportflyer

New replacement Carb leaks fuel from vent hole

I purchased a replacement carb TEC 632589 from Ebay to replace my existing carb . The edger is a McLane with H35-45642U Tecumseh engine. After installing the carb and filling the fuel tank ,  fuel starts streaming out of the carb vent hole.   I checked the float by blowing air through the fuel line input and operating the float manually and it stopped the air so the float must be working. The float position is also correct. When is there is barely any fuel  in the tank , the fuel leak stops.  The engine runs fine with the new carb in this low fuel condition.   I am at a lost what is causing this problem . Please advise . Thanks
 
 
 
9 comments Leave a comment
Roy
Remove the float and drop it in a bowl of warm water, if it bubbles it is leaking. Also ensure the anti bounce spring is correctly installed.
2018/05/28 19:36:45
AVB
You need to do a proper pressure test on the float needle and seat. Since this is a gravity type carburetor it should hold 5-7 psi of pressure without leak down while the carburetor is inverted. It is not able to hold this for at least 30 minutes then the float valve system is leaky.
2018/05/28 21:34:55
sportflyer
Roy
Remove the float and drop it in a bowl of warm water, if it bubbles it is leaking. Also ensure the anti bounce spring is correctly installed.


New carb has a plastic float so no leaks.  Anti bounce spring is correctly installed. 
2018/05/28 22:47:48
sportflyer
AVB
You need to do a proper pressure test on the float needle and seat. Since this is a gravity type carburetor it should hold 5-7 psi of pressure without leak down while the carburetor is inverted. It is not able to hold this for at least 30 minutes then the float valve system is leaky.


How to do this test ?  I don't have the means to establish the proper pressure . If the valve system is leaky is there a fix for it? 
 
Just for the heck of it , I re installed the original carb but replaced  the bowl, seal, and main jet from the new carb. Now no leaks and it works like a charm. Still need to know whether the new carb has a float needle seat problem.
2018/05/28 23:03:14
AVB
sportflyer
AVB
You need to do a proper pressure test on the float needle and seat. Since this is a gravity type carburetor it should hold 5-7 psi of pressure without leak down while the carburetor is inverted. It is not able to hold this for at least 30 minutes then the float valve system is leaky.


How to do this test ?  I don't have the means to establish the proper pressure . If the valve system is leaky is there a fix for it? 
 
Just for the heck of it , I re installed the original carb but replaced  the bowl, seal, and main jet from the new carb. Now no leaks and it works like a charm. Still need to know whether the new carb has a float needle seat problem.

What I use is a MityVac 8500 tester (pressure and vacuum model). Now you might get to use one on one of those load a tool programs that many auto parts stores have. An alternate method that is not as accurate is to loosely install the carburetor without fuel bowl upside down with fuel hose connected. Then you simply fill the fuel tank and let gravity take over. If inverted carburetor leaks then it is the sealing of the float valve that is the problem.
 
If leaky it depends on the carburetor setup but most Tecumseh uses a all metal needle and rubber seat and the seat may simply be installed upside down. But of course this carburetor is most likely a Chinese junk clone so anything possible. This one of the reasons I don't buy carburetors off eBay.
2018/05/29 09:50:17
sportflyer
It is a Chinese made Carb . The original carb is discontinued . I will  try the inverted carb method to check for float needle seal .  Anyway the carb  was so cheap and not worth returning since the Edger is now working with parts from this "junk carb" .  BTW is there any other way it could leak through the vent  besides an improper the float needle seal?  Tks
2018/05/29 10:28:58
Roy
 That is the only way gas can enter the carburetor. I thought you might still have the original brass float, if it leaks and fills with gas it will sink and not close the inlet valve.
2018/05/29 11:51:42
sportflyer
Roy
 That is the only way gas can enter the carburetor. I thought you might still have the original brass float, if it leaks and fills with gas it will sink and not close the inlet valve.


 I am currently using the original brass float with a new bowl and gasket. the chinese carb has a plastic float. Original brass float works fine ( no leaks) 
2018/05/29 13:21:04
MdStamen
Try this
Remove the seat and turn it over.
Some carburetors use a rubber seat and if it is upside down it will leak. The ridges go towards the body of the carburetor.
2018/10/21 08:54:40

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