Hi,
I have a 1811 and just replaced the fuel pump last month - its the lever action type pump runs off a camshaft near the top of the engine.
The bodies of the fuel pump are a hard plastic (at least mine were) and if its still leaking I would suspect a broken body or possibly a warped pump base. These pumps and seals inside dont last with the methanol in gas these days.
You can find replacement pumps on ebay - kohler OEM type - thats what I did and now my 18HP magum starts much faster with very little choking required.
Do you notice the oil level increasing or smelling like gas? If so your pump is leaking gas into the oil - it starts out slow and over time increases and eventually they wont start, also the leaking/seaping of gas in the area could degrade the gasket and look like an oil leak.