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Old 05-19-2011, 10:36 PM   post #1 of 10 (permalink)
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Default B&S Carb won't prime but runs otherwise

Hello Pros...I bow to your expertise.
I have a Craftsman 6 hp self propelled lawnmower with B&S engine. I have been having this problem with the carb. It just won't prime and start unless i spray fuel directly into the carb (after taking the airfilter out). I have removed the carb, thoroughly cleaned it including the brass nut at the bottom. I have also changed the gasket that sits between the prime plate (sorry, I can't think of a better name) where the prime bulb is located. I have also ensured the fuel lines are ok, the spark plug is clean, the blade is sharp etc.
But once it runs (after i spray gas directly into the carb), it runs fine until I shut it down and again back to square one, it doesn't start again.
Please guide me. Its becoming a prestige issue now ;(
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Old 05-20-2011, 12:12 AM   post #2 of 10 (permalink)
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Welcome Vaadoo!

Wonder if this might be the problem? From the Briggs carburetor troubleshooting chart:

Check Valve

Pulsa-prime carburetors. This wet bulb primer incorporates a check valve in the priming
circuit that allows fuel to fill the bulb via the fuel supply but closes when the bulb is
depressed. If the valve leaks or does not work, there will be reduced or no prime and a hard
or no start condition.


http://www4.briggsandstratton.com/mi...ence_Guide.pdf
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Old 05-20-2011, 09:40 AM   post #3 of 10 (permalink)
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I don't know how to check the valve (if there's one accessible). Also, this 4-cycle engine doesn't seem to have an adjustment screw for the air/fuel mix.
My concern is, why doesn't the priming bring any gas into the carb? If carb is sprayed with starte fluid, then it runs without any problem. And there's nothing stuck in the carb as I have cleaned it with wire and also with compressed air. The gasket is also changed. Fuel is new and ignition/exhaust is fine. Its only the starting that's causing the grief.
If you think will help, I could take pictures and see if I can attach them to my next post.
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Old 05-20-2011, 10:42 AM   post #4 of 10 (permalink)
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Ive came across this a few times also, first make sure the bulb doesnt have a hole and if its the one Im thinking of there is a grove on the air/primer side of the cleaner houseing , make sure air does pass out the hole when you press the bulb and make sure bowl gasket is sealed, it would be helpfull to know the model no. to better help out ED

Last edited by edowens; 05-20-2011 at 10:43 AM. Reason: added content
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Old 05-20-2011, 10:56 AM   post #5 of 10 (permalink)
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Hi Ed

Thanks for your response.
The model number for the Engine is 123K02-0326-E1.
You are right, there's grove on the plate and it is NOT clogged. The red primer bulb, however, has a hole by design. When I press the bulb, I do hear the hiss noise and it feels that the air goes into the carb. How can I clean the holes for the air channels in the carb? I have tried to clean it with small wire (from a bread tie) and also with compressed air. I am thinking that the air channel is not clean and that there's some gas gelled up inside and once it is clear, it should work.
I wait for your expert advice.
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Old 05-20-2011, 06:16 PM   post #6 of 10 (permalink)
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Alright...first of all and bottom line is that IT IS FIXED NOW.
Secondly, thanks to all the suggestions, I couldn't do without your guidance.
Here's what was wrong....the primer bulb wasn't sitting it properly with its white clamp and even though I could hear the hissing sound of the air being pumped, it was going sideways, rather than going into the channel.
My brother has an identical lawn mower and as soon as I exchanged the parts and did some more troubleshooting, it started working. The carb & the gaskets were all fine.
Now I can enjoy a drink on my deck looking at the lawn properly cut !!!

Last edited by vaadoo; 05-20-2011 at 06:19 PM.
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Old 05-21-2011, 01:16 AM   post #7 of 10 (permalink)
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Good to hear you got it solved and thanks for letting us know what fixed it.
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Old 09-27-2011, 11:34 AM   post #8 of 10 (permalink)
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Pretty sure this is a related issue. I have a Pulsa-prime carb on a BS lawnmower engine. Wouldn't start. I noticed that when I pressed the bulb, gas squirted out of the carb to the left (when I am looking directly at the red bulb). Covered the area of the spurt with my finger, primed three times and it started right up. How do I repair this? Thanks.
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Old 09-27-2011, 12:19 PM   post #9 of 10 (permalink)
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Glad to hear you got it fixed vaadoo. You're our resident expert on that model primer bulb from now on.

KyCats75, hmm, let's see, duct tape? No, seriously, I'm sure somebody will come along with an answer, or, in case you find the solution to your problem like vaadoo did his, be sure and come back to let us know what it was.
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Old 09-27-2011, 01:55 PM   post #10 of 10 (permalink)
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Quote:
Originally Posted by bwdbrn1 View Post
Glad to hear you got it fixed vaadoo. You're our resident expert on that model primer bulb from now on.

KyCats75, hmm, let's see, duct tape? No, seriously, I'm sure somebody will come along with an answer, or, in case you find the solution to your problem like vaadoo did his, be sure and come back to let us know what it was.
B&S support line says it could be any of three things, including a stuck ball valve, which I assume is the check valve. At this point, a trip to the shop to avoid having to cover the little hole with my finger while I prime it doesn't seem worthwhile.
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