Any small engine wizards on here?

My old lawn mower (almost 20 years) is a craftsman with a 5.5 hp Briggs and Stratton. It has always run great and still does except now it dies halfway through the lawn. It starts fine cold. No indication that it's about to die it just quits running. To get it going again I have to pump the primer 7-8 times and pull cord as many times and then it runs fine again for awhile. Where do I start?

PM Pat Fundine. Don't tell him I said this but he is a small engine genius.

Wild guess....make sure gas tank vent is open.

Sounds like rings to me

Loosing compression when it gets warm . Is it worth replacing the jug and rings on it ??

Sounds like your atmospheric relief valve has expired.

It was used too much when it was new.
Or, cracked fuel line that might be sucking air.

The diaphragm in the carburetor that pumps fuel. Easy fix.

Carburetor.
Seen it a lot. With that age (20 years) varnish and gunk will build up over time. Today's crappy gasoline doesn't help too.
Clean the carburetor out , if needed rebuild it.

I'd just replace the carb. They're not very expensive. That and a standard tube up....replace the plug, air filter, fuel filter if it has one. If it doesn't have one, get a generic small engine fuel filter and install it.

Imulsion tube is plugged or has dirt floating around in the carb bowl, it plugs the tube. No gas, no vroom vroom.




And 160 user is wrong..... I'm actually a magician..... I was titled that last week by 2 different long term customers.


I dont mean to be a jerk, but there's at least 5 answers above me that aren't even parts on that push mower.

First thing I would check is the coil. As soon as it stops running, if you have one put a spark tester on it and check for spark. If present then start checking for fuel problems. If no spark you have a coil that is breaking down when hot.

this^ is the first and easiest thing to start with

Or, you can buy a brand new Predator (Honda clone) engine at Harbor Freight for $100.

I do small engine/farm equip repair on the side. Seen this many times. It's a fuel problem. Idk what your carb type is. If it is a flo jet (bowl type) remove the bolt that holds the bowl on. Clean out the carb and bowl good with spray carb cleaner. Especially the bolt, it's ported, and the main jet which goes up to the throat of the carb. If it's a pulsa prime, (diaphragm) I suggest a kit and a good cleanout. IMO avoid cheap knockoff carbs found online, buy enough and sooner or later you'll get a junker.

This same problem has happened to my old B&S thrice.

First time the problem was a fuel tank vent that wasn't allowing air to come in.

Second and third times it was a clogged fuel filter.

Could be a lot of things. But I would definitely check these things when trying to diagnose the problem.

Go get a new one. Worn out . You got the good out of it. Use that TRUMP money you been holing up !!!!!!!!!!!!!!!!!!!!!

I knew you would throw out some technical jargon!

You want technical now...


Imulsion tube is plugged by green ethanol flakes. The engine will not run without gas. When you push the primer a few times it will break the suction on the tube from the flake of gunk. The engine now has the ability to draw gas up the imulsion tube and start. A few minutes later the flake of ethanol will get sucked up again and cut the fuel.


Most push mowers do nat have, fuel pumps - gravity feed. No jugs. Compression isn't really an issue in 4 cycle, it's more about leak down tests and valve adjustments- it wouldn't even start if those were bad. It doesn't have an electrical issue at all - it starts hot when you push the primer bulb releasing the pressure.

patfundine = majician and scholar

Dazzle them with intelligence, and baffle them with bs....

Use the highest octane gas you can get?

Happened to me once. After replacing everything else, I replaced the air filter and it ran fine.

Get and Honda when to replace the model you have.

Metering Diaphragm in the Carb. Ethanol fuel is hard on them.

Weak spark was causing starting problems with my Toro self-propelled until I replaced the magneto. In your case I, like others, suspect a fuel problem.

I think the left rear tire is low on air and causing the problem.

I'm sure a man of your quality has had this problem in the past....... I can only assume the hole was caused by a bullet, or possibly a shovel that in the heat of the moment missed hitting the snake and got the mower tire.

That statement pretty much captures my mechanical ability. Usually when I bring something in for repair and they ask what is wrong with it I tell them "It's broken and doesn't work". If I actually knew what was wrong with it I may fix it myself.

May need to rotate the tires. uneven wear is bogging it down.

Check your flux capacitor.

Lots of likely possibilities listed above.
I had a situation recently with a chain saw. It turned out the gas pickup line in the gas tank had become soft over time, and the resistance caused by the little filter on the end of the line in the tank would cause the line to collapse on itself from the vacuum caused by pumping of the gas.
Shut it off and it would start up just fine, but soon after it ran hard for a bit it would die from lack of gas.

A lot of my problems went away when I started using non-oxy hi octane premium

Dump the gas and refill with non-ethanol if you can find it
Perfect setup for a $7.00 can of Seafoam experiment ?

Its the Q32 Millenium Space Modulator (Marvin The Martian)

Wow some of you guys are way smarter than you look. I took the thing out of the middle of the gas cap and cleaned all that up. Put it back and managed to mow the whole lawn without stopping. You'd think I would have thought of that having run small outboards with vented tanks for nearly 40 years. Glad I asked. Thanks for the help.

Sounds like a bad turboencabulator....

I would still check the carb out. Could be a fluke that it didn't die. I would be really surprised if there wasn't something in the bowl floating around.