MTD 998 with 18hp B&S Vanguard Cranks, but won't start

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  #1  
Old 12-05-17, 08:34 AM
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Post MTD 998 with 18hp B&S Vanguard Cranks, but won't start

Howdy Everyone!

I hope you are all doing well today.

I am currently experiencing some issues getting my lawn tractor started. It is a MTD 998 (also known as a White 1855) equipped with a Briggs and Stratton 18hp Vanguard V-Twin engine (model # - 360447, type - 0119-01 4962, code - 93072211). This is a tractor from 1994, so it definitely has some years on it and had been through a few owners before I picked it up. As it sits, the motor will crank (most of the time), but fails to fire completely. Occasionally, it will backfire out of the top of the carb if I have the choke on.
HISTORY - I've checked that both plugs are sparking, replaced the air filter, cleaned out the carb and checked the fuel solenoid function, replaced the ignition coils (and set their gaps correctly, replaced the kill wire for the coils, and replaced the spark plug boots. I did all this work to resolve a prior issue, where the engine was only firing on one cylinder. For a few days, it was running really great. But just a day ago, I went to start it and the starter was not able to turn the flywheel. After trying to manually turn the flywheel, I noticed that there was a grinding noise and turning the flywheel (via the PTO pulley) was exceptionally difficult. After rocking the PTO pulley back and forth, it started to free up and turn more easily, but then it would catch again after about a half a turn. All the while, the grinding noise continued. I'm not sure if I could be facing a busted flywheel key (looked fine when I tore it down for the coil replacement) or possibly even a busted push rod. After tearing it down last night to inspect the flywheel (again), I noticed that the grinding noise went away, and it started cranking consistently again (but still not starting). Any guidance you could provide would be much appreciated.

I recent found a snow blower attachment for this baby and can't wait to put it to use this winter.
Thanks in Advance,
WMFF
 
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  #2  
Old 12-05-17, 10:11 AM
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Shake the engine back and forth a number of times, then drain the oil. Check for metal filings. If you find those in the oil, plan on a major overhaul.
 
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Old 12-05-17, 10:15 AM
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@marbobj

Can do. I actually just very recently changed the oil and didn't see anything unusual. Literally a couple of days after getting the coils replaced.

Best Regards,
WMFF
 
  #4  
Old 12-05-17, 10:21 AM
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It could be something external (possibly a coil slipped), but I would check it. It doesn't take that much oil. Apparently there wasn't anything in the old oil you noticed?
 
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Old 12-05-17, 10:27 AM
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@ marbobj

I'll be sure to check the oil this evening. Nothing stood out to me after the last oil change, but to be honest I wasn't looking closely. I'll report back with what I find. Thank you for a direction to follow!

Best Regards,
WMFF
 
  #6  
Old 12-05-17, 05:34 PM
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Are the plugs wet with gas? Does the oil smell like gas? If the starter couldn't turn it over, the carb could have filled the cylinders with gas and then with you turning it by hand, the starter would still have been engaged, so it would have been turning the starter with the engine when you tried to turn it with the PTO pulley. That would have made it hard to turn and would have made the grinding sound that went away as you moved it because the spring finally worked the drive gear back away from the flywheel.
 
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Old 12-06-17, 03:20 AM
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@ Cheese

I knew you were good, but not THAT good. You absolutely hit the nail on the head. The engine was flooded and the starter gear was remaining engaged with the flywheel. These paired together created the no start issue and the aforementioned grinding noise. I let everything air out last night and she started right up! I sure feel silly now. Thank you so much for everyone's help and support.

Now I get to fit up that sweet snow blower!!! Yipee!

Best Regards,
WMFF
 
  #8  
Old 12-06-17, 03:25 AM
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@ marbobj

Cheese helped me figure the issue out. But I did end up checking the oil, as you indicated, just to be sure. Everything looked good, besides being a bit dark in color for such a recent oil change. Thanks again for the guidance.

Much Appreciated,
WMFF
 
  #9  
Old 12-06-17, 08:09 AM
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You still have a problem with what flooded the engine. It means the carb needs some work on it to prevent future flooding. Once that is remedied the oil needs to be changed to get the gas out of the crankcase.
 
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Old 12-09-17, 11:17 AM
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Yep, sounds like you have a sticking needle or trash in the needle seat area.
 
  #11  
Old 12-18-17, 12:29 PM
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Good Afternoon Gents,

Funny that you guys mentioned this (and boy am I glad I came back to the forum to check on these comments)..... The tractor refuses to start now. It turns over just fine, but nothing beyond that. Occasionally it will backfire when I attempt to crank with the choke out. The smell of gas is very strong in the air as well. I presume that I should start by taking the carb off and giving it a good cleaning? I checked for spark and fuel, which are both there. The air filter is brand new as well.Thanks again for the continued support and guidance.

I still haven't gotten to try out that snow blower!!!! XP

Best Regards,
WMFF
 
  #12  
Old 02-07-18, 05:27 AM
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Hi Everybody,

Unfortunately, I am back looking for advice again. I had the tractor running for about 3 days and got the snow blower fitted up (along with getting some other maintenance done). After moving the tractor back outside for an evening, it refused to start the following morning. Battery was fully charged, wasn't even that cold. I pulled the carb off and give it yet another good cleaning, but this time it did not resolve my issue. I've definitely got spark, air, and fuel. This time around, the engine won't even fire up with starter fluid. The only thing that happens now is occasionally some fire will come belching out of the top of the carb when I have the air filter pulled off. I am at loss for what to do next. As always, your help is greatly appreciated.

Best Regards,
WMFF
 
  #13  
Old 02-07-18, 05:30 AM
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MTD 998 with 18hp B&S Vanguard Cranks, but won't start

Hi Everybody,

Unfortunately, I am back looking for advice again. I had the tractor running for about 3 days and got the snow blower fitted up (along with getting some other maintenance done). After moving the tractor back outside for an evening, it refused to start the following morning. Battery was fully charged, wasn't even that cold. I pulled the carb off and give it yet another good cleaning, but this time it did not resolve my issue. I've definitely got spark, air, and fuel. This time around, the engine won't even fire up with starter fluid. The only thing that happens now is occasionally some fire will come belching out of the top of the carb when I have the air filter pulled off. I am at loss for what to do next. As always, your help is greatly appreciated.

Link from prior post - https://www.doityourself.com/forum/o...ml#post2684357

Best Regards,
WMFF
 
  #14  
Old 02-07-18, 05:44 AM
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I don't see where you have checked compression??? Sounds like it is time to verify it still has some.
 
  #15  
Old 02-07-18, 06:23 AM
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BFHFixit,

Good call. I've got a compression tester that I'm borrowing, so I'll hook it up tonight and give it a crank. Just for my knowledge, what kind of pressure readings should I be looking for?

Much Appreciated,
WMFF
 
  #16  
Old 02-07-18, 08:24 AM
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Briggs does not publish numbers: http://www.briggsandstratton.com/lam...ession-reading

However, I still do check and look for 80-100PSI on a single but should be over 120 on a twin cylinder with no compression release. Some twins will only have a CR on one cylinder. 150-170 is what i find on healthy cylinders without the CR or it being disabled. You can disable the CR by removing the push rods, but then the starter may not have enough to pull it through.

Quick easy check might be to just give each cylinder a couple squirts of oil in the plug hole. If it is rings this might get it to fire.
 
  #17  
Old 02-07-18, 12:50 PM
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Belching out the top and not firing with ether makes me think it's flooded again.
 
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