I have a push mower with a briggs and stratton 3.5 hp classic. The old primer bulb developed a crack in it so gas would leak out when priming but it would start and run until no more gas would go into carb I had to re-prime it to get it running again. I replaced the primer bulb but now I can't get it to prime at all no matter how many times I push it. If I pour some gas into carb it will run but for some reason it won't prime. I did notice the old primer bulb did not have a tiny vent hole in it like the new one does. Any suggestions?

Does it stay running after you squirt fuel in the carb opening? If yes, then there may be a pin hole leak in the hose going from the fuel tank to the primer bulb and it is adding air to your carb.
Thanks

If its identical it should work ,if not take the old one to a mower shop,to get correct one and make sure the choke is going right on when the cable is in choke position.

sounds like the bulb is bad it can be replace on the mower

Your primer bulb has a pin hole in it. The part number is 5085H This is an aftermarket replacement for the original 694395 primer bulb.
Web image search:
http://www.google.com/search?q=Briggs%20and%20Stratton%206.75%20Hp%20Primer%20Bulb%205085H&rls=com.microsoft:en-ph&oe=UTF-8&startIndex=&startPage=1&um=1&ie=UTF-8&tbm=isch&source=og&sa=N&hl=en&tab=wi

Another part number (original Part) is 694395
http://www.discountsawchain.com/servlet/the-401/Briggs-%26-Stratton-Primer/Detail

http://www.briggsandstratton.com/engines/shop/parts-and-accessories/?part=694395

Thanks for choosing FixYa,
Kelly

I had a B&S lawn mower engine that did this unless I kept pushing on the prime button and I found I had a Cracked primer rubber bulb. Maybe you have something similar or another type or carb problem.

You can try pumping primer bulb 10-15 times instead of 3 or 4 that manual probably suggests. We have a craftsman 22 inch cut push mower with a 3.5 H.P. BRIGGS &STRATTON engine and if you don't prime it at least a dozen times it will not start. It is possible that you have a small hole in your primer bulb in which case it can't create suction to bring gas to carburator. If this is the problem you can purchase a new bulb and seal at most larger SEARS stores or service centers.I would guess that if you have manual for mower you can get part number and phone number to get new parts .Hope this helps. Thanks

Your carb needs to by cleaned out. Needs to be taken apart and cleaned with carb cleaner. There is also a gasket that needs to be replaced. It collapsed and not letting gas in the carb.

Guessing you have a briggs and stratton motor with a tank mounted carb.Remove the tank and carb. from the mower and replace the rubber diaphram between the carb. and tank and clean it while its off

Briggs made primers with and without holes in them. In my shop it is common to see them transposed on engines.
Take down the MODEL TYPE CODE numbers and check here to see if yours should have the primer with or without the hole in it.

Click the Parts Lookup box in the center of that page.
Next, drop down the menu on the left to Briggs & Stratton. Set the tab at the top to MODEL.
Next, type in the model number and click search.
From the results page, select your exact type number. Your individual parts views will then be listed on the right side of the page. You'll get the idea!

Hope this helps.

Drain float bowel
check for water .