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Old 03-08-2011, 06:05 PM   post #1 of 10
Spamburger17
1994 MTD 848 18.5 I/C
 
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Default B&S 18hp I/C troubles

I have 1994 MTD Pro 18/46 GT, model 848. I had started my tractor to move it and was cold out, so i still had the choke on while moving and flooded the motor, which was expected as it warmed up. I let it sit for awhile and then it would no longer turn over well or start. It acts like one cylinder isnt firing. I changed the plugs, and also grounded them and cranked, to check for spark and i had a good light blue spark from both new plugs. Also, with no spark plugs installed = no compression, i cranked the engine to make sure no crank or rod damage was the cause, and it spun right over like a fresh/new engine. I reinstalled the plugs, and again acting like it wouldnt fire, slowing down during compression stroke from one cylinder. I can pull the one plug and it will crank fine too, so it is most likely the one cylinder. Like i said, it has spark, but maybe not enough? I also pulled the cylinder head to make sure no valves were stuck and cylinder wasnt damaged. Before this it ran like new. Any ideas or help appreciated. If i were to try a compression test, what would the spec psi range be? heres a link to a video of it trying to crank.

http://www.youtube.com/watch?v=fXwY3NdkDCU
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Old 03-08-2011, 09:26 PM   post #2 of 10
themidniteryder
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Default Re: B&S 18hp I/C troubles

Put a volt meter on the battery and try cranking over, observing the voltage drop. If it falls way down, like to 5-7 volts while cranking, fully charge or swap in a known god battery. Sounds like it just doesn't have the juice to turn it over. At least its a cheap starting point. Let us know what happens.
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Old 03-08-2011, 09:58 PM   post #3 of 10
38racing
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Default Re: B&S 18hp I/C troubles

If it's OHV might be time to check valve clearance
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Old 03-09-2011, 05:36 PM   post #4 of 10
Spamburger17
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Default Re: B&S 18hp I/C troubles

I think ill try hooking up another battery (multi meter took a dump) and see what happens. ive done a scan of most of the mechanical and it seems to be sparking the plugs. It cranked fine a few weeks ago, but maybe its time came. Ill pull both heads to make sure all the valves are working too. Its not overhead valve, but i could check valve clearance too. It seems more like too much compression or not enough cranking power.
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Old 03-09-2011, 06:19 PM   post #5 of 10
Tater305
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Default Re: B&S 18hp I/C troubles

sounds like a battery or starter problem not a motor related problem id start there first
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Old 03-09-2011, 08:03 PM   post #6 of 10
themidniteryder
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Default Re: B&S 18hp I/C troubles

If you have never had them off, now would be a good time to pull the heads and decarbon. I dont think there is enough build up to raise your compression a lot. If it had that much carbon you might also be hearing what sounds like the piston slapping the head. But defiantly try another battery first, and even another starter if you have a spare laying around.
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Old 03-13-2011, 06:26 PM   post #7 of 10
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Default Re: B&S 18hp I/C troubles

I tried jumping the battery so most likely the starter is going bad. I ordered one, hopefully all ill need.
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Old 03-14-2011, 02:40 AM   post #8 of 10
rustyrideon68
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Default Re: B&S 18hp I/C troubles

Hope you get it going again.
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Old 03-17-2011, 08:02 PM   post #9 of 10
Spamburger17
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Default Re: B&S 18hp I/C troubles

Well, the starter fixed cranking issues, better than ever. BUT, a rod started knocking while i was driving it around, YAY. I thought about rebuilding it, itd be an interesting experience, but it looks like itll be about 200 or more in parts with gasket kit, rods, pins and rings, if the crank is still good. Ive already got alot in it rebuilding the mower deck and other things so i figure may as well do this too. I doubt i can get a new or rebuilt engine that cheap. Any thoughts?
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Old 04-03-2011, 11:35 AM   post #10 of 10
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Default Re: B&S 18hp I/C troubles

Before tearing into the engine, you said you had it running with the choke on and it died. It wouldnt restart.

Try removing the spark plugs and put a teaspoon of oil down the cylinder, Turn by hand to move oil all around cylinder, replace spark plugs and let sit for a day or so. Try and restart and see if the knock went away. It maybe piston slap from running while choked and no oil on the cylinder wall. Just an idea.
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