Primer Problem - Snowblower Forum : Snow Blower Forums
 
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post #1 of 8 Old 09-12-2016, 09:27 AM Thread Starter
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Primer Problem

My Ariens has a Briggs and Stratton 305cc. When I push the primer bulb, fuel is coming back out of the carb. With the air cover removed, I can see the fuel is coming up the tall tube in the centre of the carb throat, then flowing backwards out of the carb. Any ideas for the fix?
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post #2 of 8 Old 09-12-2016, 11:07 AM
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With my limited knowledge and some quick videos on how carbs work, if it just seems to be cycling fuel between the bowl and the primer bulb, perhaps one of the one way valves isn't functioning correctly. This would not allow for a proper vacuum to cycle the fuel through the system?

Was the bowl dry originally, or could it be old fuel that was still in it. If its old fuel im thinking the valve at the primer bulb is stuck. (Just talking out my butt and guessing) Does it run at all and you are just concerned the primer isn't working correctly? As an after thought maybe the float isn't working correctly closing the needle in the proper fashion. I am also not sure what you mean by the throat if you mean its pumping fuel and you can see it pumping into the venturi air champer (throat?) then again I think its the valve at the primer pump is stuck closed. Might need to do a cleaning of the carb.

Hope someone gets on with some more small engine knowledge but hopefully that might get you started.

Used this to get an idea on what the little primer does. While the video is for a 2 stroke carb I believe the principles are the same.
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post #3 of 8 Old 09-12-2016, 12:54 PM
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how many times are you pushing it when the fuel comes out of the carb? you shouldn't have to push it more than a couple of times to prime system.
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post #4 of 8 Old 09-12-2016, 02:11 PM Thread Starter
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Only one push on the primer bulb is causing fuel to come out of the carb throat (venturi). The snowblower starts and runs perfectly now but my concern is when the cold weather comes, the primer will need to work. The fuel should be flowing into the carb and not back out of the air cover.
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post #5 of 8 Old 09-12-2016, 03:01 PM
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I don't have much experience with Briggs snowblower engines, but on a Tecumseh that would be normal.

The priming system isn't very sophisticated - when you press the bulb, it momentarily increases air pressure above the fuel in the float bowl, causing fuel to flow up through the jet into the venturi as you've seen. It'll typically flow down both sides of the venturi - some goes toward the engine, the rest goes toward the air cleaner. It's sloppy but that's just how they work.

Was the 'blower sitting on a level surface when you examined it? If it was tilting toward the carb intake, that might have made more fuel come out the intake.

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post #6 of 8 Old 09-12-2016, 05:11 PM
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Quote:
Originally Posted by ELaw View Post
I don't have much experience with Briggs snowblower engines, but on a Tecumseh that would be normal.

The priming system isn't very sophisticated - when you press the bulb, it momentarily increases air pressure above the fuel in the float bowl, causing fuel to flow up through the jet into the venturi as you've seen. It'll typically flow down both sides of the venturi - some goes toward the engine, the rest goes toward the air cleaner. It's sloppy but that's just how they work.

Was the 'blower sitting on a level surface when you examined it? If it was tilting toward the carb intake, that might have made more fuel come out the intake.
I've had them do that too. It might just be working too good! On my old Toro you can push 4-5 times, on the new Husky twice and it drips a little.
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post #7 of 8 Old 09-12-2016, 06:59 PM
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Perfectly normal.
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post #8 of 8 Old 09-13-2016, 08:40 AM Thread Starter
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Sounds like I've got nothing to worry about. I'll just tilt the machine inward a little when priming. Thanks to all for your help
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