Can't get prime from bulb

waylonJ

Member
Joined
Mar 5, 2020
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I'm working on one of the B&S carbs which sit on and inside the gas tank on a 3.5 HP Murrary mower.
The mower ran poorly and was surging so I cleaned the carb 2 times and still no luck so I got a China-Bay carb and when I attached it I could not get the primer bulb to squirt gas into the carb. The gas tank was half full of gas. I am pretty confident that I should be able to see the ol' squirter in action without the carb & tank bolted to the mower but with the carb attached to the gas tank with the mounting screws. On this new carb (not priming) I thought it was a defective primer bulb so I swapped it out with a brand new bulb. Still no prime / squirt was visible. For the heck of it I bolted everything back onto the mower and it would not start, I could tell it was not getting a prime.

So...I put the old carb back on and no prime/squirt. Okay. I put a brand new bulb on the old carb - no prime. I am beside myself. My only theory is a messed up gasket / diaphragm which sits between the carb and the gas tank. There is a diaphragm and a gasket. I have it so the diaphragm sits on the gas tank directly, then the gasket, then the carb. Could this be wrong? I am also nicking the diaphragm and gasket everything I remove it so I may have damaged it.

I just don't know where to look to troubleshoot this further.

Any advice fellas?

carb.JPG
 

Rivets

Lawn Royalty
Joined
Mar 11, 2012
Threads
55
Messages
14,681
First I would replace the diaphragm and gasket. Second, when you installed them the diaphragm goes against the tank first, then gasket, then carb and tighten the screws slowly, in a crossing pattern. Did you remember to install the pulse spring?
 
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