I have a Briggs and Stratton mower that runs for a few seconds after being primed and then stops. If I continue to press the primer button it will keep running.

I've tried to change fuels, clean carb, keep nut with the little hole, replaced spark plugs and air filter. Still no luck.

Any suggestions?


So it turns out that a few of the gaskets on the carb were stuffed (I also thought the fuel bowl was the carb originally, my bad). I bought the carb rebuild kit and replaced everything I could. The carb itself was pretty clean as well.

Here is a photo of the carb when I took it off

enter image description here

Mower is working awesome now. Thanks for your help!!

  • Apparently it's a lean condition. How did you clean the carb? Are all fuel passages clear?
    – isherwood
    Commented Jan 23, 2016 at 1:03
  • All the fuel lines that I could see were clear. I took everything apart and checked for sludge is dirt. The fuel bowl was clean getting lots of fuel.
    – tyelford
    Commented Jan 23, 2016 at 2:33
  • The "...nut with the hole.." is that the drain nut on the carburetor bowl?
    – ojait
    Commented Jan 23, 2016 at 3:07
  • 1
    How did you clean the carburetor? Was it disassembled and soaked in a cleaning solution?
    – ojait
    Commented Jan 23, 2016 at 3:08
  • How old do you think the engine is? And what's the Horsepower or piston displacement (cubic inch)?
    – ojait
    Commented Jan 23, 2016 at 3:16

2 Answers 2


There are so many variables that can keep a small engine from running properly. The best way to find the exact cause of a "no-start" issue is to ensure that the engine has the four necessary things for it to run: fuel, compression, spark and air. If any one is missing or inadequate the engine won't work.

Since it runs, but then stops you can you can assume the plug is igniting the fuel. Check the tank for particles blocking the fuel line, check the gas cap vent for blockage, and clean the air filter. If the gas has been sitting with no Sta-bil preservative the fuel may have crystallized in the carburetor which would mean a disassembly and a soaking in a bath of parts cleaner. Add fresh fuel before re-starting.

Pull the plug and place your thumb over the cool engine plug port. Pull the starting cord on the exhaust stroke the pistons' force should be felt. If not you may need piston rings.


Difficult to troubleshoot this online, but it sounds like you need to replace the diaphragm that sits between the fuel tank and the carburetor. I'd pick up and install a carb kit before trying anything else (if nothing else they're only a couple bucks and include the part). The fact that it runs when you manually inject gas with the primer bulb points to the carb, and there isn't much else that can go wrong with a clean carb on these things. I'm guessing you'll find either a tear or a bad seal on the existing one.

  • Are you able to have a look at this parts guide and see which part the diaphragm is? jackssmallengines.com/Jacks-Parts-Lookup/Model-Diagram/…
    – tyelford
    Commented Jan 27, 2016 at 4:13
  • @tyelford - Hard to tell without looking at the carb, but it looks like on that model it's a detent on the air cleaner gasket. I'd get the carb overhaul kit though - you'll need to replace all the gaskets, so it's pretty much getting the rest of the included parts for free...
    – Comintern
    Commented Jan 27, 2016 at 5:29
  • @Comintern- do you mean "gasket" that sits between the tank and carb? or "diaphragm"?
    – ojait
    Commented Jan 27, 2016 at 17:40
  • @ojait - On a lot of these engines, the diaphragm is part of the gasket. For example, on my mower engine there's a port in the carb that matches up with a recess on the fuel tank. The gasket sits between the two, but doesn't have a cut-out. That's the carb diaphragm.
    – Comintern
    Commented Jan 27, 2016 at 18:40
  • @Comintern- So the two have the same function or can be used interchangeably? Sorry, I'm not trying to be argumentative, but I've never heard of a gasket/ diaphragm.
    – ojait
    Commented Jan 27, 2016 at 21:40

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