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  #1  
Old 06-02-2012, 08:49 PM
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G.M.Landscaping G.M.Landscaping is offline
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Stihl FS100RX trimmer leaking gas into air filter.

My FS100RX is filling up the air filter with gas when not in use. Either in a horizontal or vertical position. I tried cleaning the carb a couple times with no luck. Instead of ordering a carb kit I ordered a new carb. It didn't come in yet, so I took a good working carb off of my FS90R and put it on till it comes in.

Hung it up on my trimmer rack in the shed(engine up/trimmer head down). Now its doing the same thing. What's making two carbs do this? S88 & S131B carbs. It's definitely dripping out of the air filter assy. Gas cap and tank is dry.
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Old 06-03-2012, 08:43 AM
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More then likely it's your tank vent, small black fitting on the top of your tank with a single hose that runs in to the back side of the air filter housing. Set it in the rack without the air filter and cover and keep your eye on the small hole in the lower left hand corner of the aluminum case.
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Old 06-03-2012, 09:14 AM
Duekster Duekster is offline
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Floats could be stuck from old gas.
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Old 06-03-2012, 12:16 PM
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G.M.Landscaping G.M.Landscaping is offline
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Quote:
Originally Posted by MowerMedic77 View Post
More then likely it's your tank vent, small black fitting on the top of your tank with a single hose that runs in to the back side of the air filter housing. Set it in the rack without the air filter and cover and keep your eye on the small hole in the lower left hand corner of the aluminum case.
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Well I did that and that's where it's coming from. So I pop it out and it breaks. Guess it needed replaced anyways.

Is this a valve that relieves pressure buildup in the tank?
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Old 06-03-2012, 01:58 PM
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Nope one way valve to replace the used fuel from your tank with air, all fuel tanks are vented either by the cap vent or some kind of external vent. If not once the suction was too great it will slow or stop the flow of fuel and sometimes suck in the sides of some tanks.
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Old 06-03-2012, 04:19 PM
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Quote:
Originally Posted by MowerMedic77 View Post
Nope one way valve to replace the used fuel from your tank with air, all fuel tanks are vented either by the cap vent or some kind of external vent. If not once the suction was too great it will slow or stop the flow of fuel and sometimes suck in the sides of some tanks.
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So what happens on a hot day when pressure builds up in the tank?
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Old 06-03-2012, 04:25 PM
jtsnipe jtsnipe is offline
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So what happens on a hot day when pressure builds up in the tank?
Fuel injection.
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Old 06-03-2012, 05:34 PM
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Quote:
Originally Posted by MowerMedic77 View Post
Nope one way valve to replace the used fuel from your tank with air, all fuel tanks are vented either by the cap vent or some kind of external vent. If not once the suction was too great it will slow or stop the flow of fuel and sometimes suck in the sides of some tanks.
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So it's a one way valve that go from the filter housing to the tank. What happens if you plug the hose until the new part comes in?
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Old 06-03-2012, 09:45 PM
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Fuel injection.
The 420 blower is exactly the same setup. I have never seen fuel come out of that tube but I sure know that a lot of pressure builds up in the tank on all three of my blowers.
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Old 06-03-2012, 09:48 PM
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So it's a one way valve that go from the filter housing to the tank. What happens if you plug the hose until the new part comes in?
Thought I explained it pretty well, but your tank won't vent.....Stihl says that the lock cap with the orange center is also a vented cap I guess double redundancy.....
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