To answer you questions we really need to know WHICH 18.5 B&S you have. Model number, as there are several that fit that description and some are radically different. IF this happens to be an OHV single cylinder, I have detailed instructions for adjusting the valves which is likely the problem. Address below, put in proper format and remind me. IF it is a horizontally opposed twin, I have a list of possible causes for hard cranking. Either way, you have likely fried the starter by holding it engaged too long trying to make it turn the engine. Brief engagement followed by a considerable longer cooling period must be used. B&S starters are highly interchangeable so a good used one should be fairly easy to find. Walt Conner wconner5 at frontier dot com

Did you try it with the fuel cap removed, the vent may be plugged. Remove the pump and with a finger over the inlet fitting,suck then blow through the impulse hose fitting. You should feel suction on your finger. If not, replace the pump. Probably p/n 808656.

I believe tomplum has it right. I just went through this last year with the same engine in a Cub Cadet. Same symptoms with oil oozing out of the fuel pump when running. New head gasket solved the problem.

Mr Kapaun, my most humble apology. I am not computer literate, yet, so I was not aware the two items I sent were not to be together for the readers. I had the filler cap off while I was cranking the engine over to get the gasoline out of the cylinder. That's when the air/oil residue came out the filler. It would appear I need to seek a repair person locally to fix the engine, as I am having a difficult time putting in words what the engine problem is. Again, to all, I apologize for my making two entries on the same problem. Thank you all so much.