Craftsman w/ 20HP Briggs & Stratton Won't Start

Craftsman Lawn Mower
917.272140
46" mower
20.0 HP engine

It's the 407777-0121-E1 B&S engine according the the owner's manual, INTEK engine.

Got the mower out to cut the grass like normal. Engine ran pretty decent for its age and lack of maintenance, had to pull the choke out maybe 1/4 for a smooth run. Anyway, everything was fine, fired right up, started cutting the grass. Got about 20ft into cutting and suddenly I lost power and engine just cut off, died and spun down to a stop. No bangs, no pops, no explosions or "weird" sounds, almost like I ran out of gas or something. Sat there and cranked the engine over, nothing. No signs of life when I'd crank no matter what I did. I pulled the hose off the fuel pump outlet and got no fuel spitting out when I cranked the engine over.

Now at this point I pushed it back into the shed and figured it was the crap fuel pump (plastic POS with the diaphram that I seem to have to replace once a year) and went in to order a new one. I also at this point decided I'd pull the hydrostatic transmission out for repair as it was clicking and I'd lose drive power on slight inclines (ended up having a broken tooth on the spur gear on the differential) which was annoying.

Slapped my transmission back in, changed out my fuel pump with a new one, and tried to start it up. Nothing. Engine just cranks over with no signs of life. Checked for spark at both plugs and seems plenty strong (arced about 3/8" to the case) and the spark looks strong in the gap. Pulled the fuel line from pump outlet and STILL NO GAS getting pumped! Pulled the inlet line off and blew compressed air into the tank and got bubbles so it's not clogged on the tank outlet. Filter wasn't clogged (removed it from the equation for troubleshooting). When I crank the engine I didn't feel suction on the fuel pump inlet either. Then I checked the (relatively new) vacuum hose coming from the valve cover that drives the pump and found no cracks or leaks there.

At this point I don't know what the hell is going on. I got some ether (starting fluid), removed the air cleaner, and sprayed it in the intake while cranking and it's still not firing.

I pulled the plug(s) one at a time and put my finger over the hole and when I crank I can't feel any pressure on either side but I'm not sure this is a worthy test as maybe there's a compression relief working as the engine isn't spinning fast enough?

I'm at a loss at this point. From what I've researched people are saying that I've got no vacuum for the pump cause the breather valve is stuck open? But the damn thing should run on ether! Blown head gasket? But seems like it should still run, just make tons of smoke or something. I'm getting NOTHING!

Please help, my grass is getting crazy tall with all this rain we've been getting!

Mike

 

If you feel nothing from the spark plug hole when cranking, you have internal engine problems. Stick a straw down the plug hole and turn the engine by hand to see if you feel the piston moving. If not, your engine is blown. Was it low or out of oil?

 

Ahh, a straw is a good idea. I was going to get the borescope from work and poke it in there but a straw would work too. Not sure on the engine oil, it was fine at the beginning of the cutting season...

I'll be honest, if the engine is shot I wouldn't be tooooo surprised... the thing is 16 years old, cut 4 acres in a sitting almost every week that was really rough/bumpy and the previous owner (my dad) never did much preventative maintenance; just fixed stuff that broke that'd keep it from cutting.

I just ran out and poked a straw in one of the plug holes... no movement when I turned the engine over with my hand. I'm pretty sure I had the end of the straw on the piton, inserted it along the axis of the spark plug hole. It was also at this point that it seems strange that I can just place my palm on the mesh finger guard on the top, spin it, and get almost 3 revolutions from the engine...

I have no idea what prices are for parts like that, am I better off with another used purchase, find parts, fold in and push mow, or invest in a new rider? I'm thinking I'd be best off not putting another dime into it...

Mike

 

What are the chances that there's a key or something on a shaft that's sheared or something? Should the ground drive pulley on the bottom rotate as I crank/spin the engine by the flywheel at the top? I haven't checked that but could. If they're both spinning then maybe that'd indicate something broken with the connecting rods. If it doesn't spin then it could be the crank shaft is broken in half or maybe a key keeping the flywheel and starter ring gear is gone or something and that's why I'm not getting the cylinder moving?

It seems like there should be more noise if something catastrophic was broken in the engine... but hey, what do I know.


EDIT* Alternatively, any sense in trying to engage the electric blade clutch and then manually rotate my blades and see if I can turn the engine over with the plugs removed and a straw poked in there? Would that tell me anything?

 

No, your engine is toast. I'd guess it ran out of oil. I'd look for another used one on craigslist or something like that, or just get another mower if it has that much wear, tear, and neglect.