willshak wrote:

My 18 hp B&S on my Garden Tractor won't continue to run. It is about 10
years old.
I mowed the grass a few weeks ago and it ran fine until I was almost
done with the 1 acre mow job.
It started to lose power as I was climbing a small hill in the yard,
then it died. I was able to restart it, but I had to close the choke
fully in order for it to stay running, and the it only ran for a short
distance before it shut off again.
This week, I could not get it to stay running for more than a few
hundred feet before it shuts off like it no longer got gas or the key
was shut off.

What I did:
Pulled the fuel filter off and blew through it from both ends. No
obstructions, and I could see the screen was clean inside. I blew
through the gas line that goes to the gas tank and was able to blow
bubbles in the tank.
I replaced the fuel filter with a piece of tubing, just in case it was
the filter.
I removed the gas line from the carburetor and the gas ran out freely.
I pulled the cover off the carburetor and checked the diaphragms. No
holes, tears or problems.
I ran it with the air cleaner off and the in-line fuel filter removed.
No difference.
The gas is not old and the tractor is used year round for lawn mowing
and snow blowing.

As far as I can figure, it runs out of gas or perhaps heats up to where
it seizes up. Is there an oil pump that may have gone bad?

I'll bet the diapragm has lost its flexibility and the accelerator pump
isn't working any longer. (You ran it dry last Fall, right?). Just by
a rebuilding kit and replace the diaphragm. Don't bother with changing
the jets and other small pieces because you'll screw it up.

While you're at it, check that the carburetor floats don't have a hole
in them. And, check the needle valve by blowing into the fuel inlet
and gently moving the floats up and down. Sometimes dirt gets into the
needle valve and it can't shut off, flooding the engine.