Small engine question.

mbalbritton

mbalbritton

#@$%!
Joined
Mar 22, 2005
Location
Lakeland, FL
I have a Troy Built 42' riding mower with an 18hp twin cylinder Briggs.

While mowing, it started loosing power and then died. I haven't been able to get it started again.

Things I've done.
New plugs
New fuel filter
Field stripped carb and cleaned it
Checked gap on coil to flywheel
Cleaned coil and magnet surfaces
Checked intake for blockage
Checked exhaust for blockage
Checked seat kill switch contacts

Holding the plug to a ground I get little to no spark. There is definitely fuel coming from the jets in the carb.

It turns over strong and fast, it just will not fire.

Suspecting the coil, but they say these coils rarely go bad. Id rather not throw parts at it.

What else can i check?
 
Compression check with a gauge?
 
plugged fuel line and or fuel tank cap vent; remove fuel cap and blow the fuel line out backward (watch the air pressure) and see if that works. Next check the pin-hole vent in the fuel cap... it could be clogged.

I was having tonssss of trouble with my Briggs and it ended up being a plugged vent hole in the fuel tank cap.
 
New Cap, and I've tried it with the cap off. Initially I found pieces of the old cap in the bottom of the tank and thought for certain that was the issue. dumped, flushed and cleaned tank and hoses., replaced filter, cleaned out carb. Carb pumps fuel into intake. no doubt about that.

Don't have a compression checker to check. I wonder if that's on the loan a tool program at the parts store?
 
Yes, and it doesn't take much movement to shut one of these down. I usually find them completely sheared, but I've heard of just a little smearing killing them. Hope you've got a puller to get the flywheel off! When I did the one on my 18hp twin, I didn't, but I made one out of some flat stock I had. When it let go, it sounded like a .22 going off!
 
I have a small puller. maybe 4" deep and up to 6-8" wide. Guessing that ain't wide enough if I have to grab the flywheel. Guessing you had to press it back on , or is there a nut to run it back down with?
 
I pulled only one 15-18 years ago? By hanging the flywheel from a large oak limb (chained to the flywheel) and bouncing up and down on the mower front. Used the mower itself as leverage. It still took hours and when it went, so did I to the ground. I remember that early age moment well...

I'd imagine applying heat to the flywheel would help out??? Not a fun job so I'd second the compression check to make sure you're not beating a dead horse. I have a gage you can use but not borrow for I use it regularly. Located in N. Durham. You've been to my shop once. Also have a leak-down tester if compression isn't good to help decypher the problem if you wanted to rebuild.

Starting with fresh gas couldn't hurt if water possibly got into it. If you have float bowles on the carbs, you can drain and pull them to see if it had water in it. Look for red coloration at the bottom.

I'd definately plug away at the easiest first before pulling the crank. I knew nothing about a compression gage in my youth when I pulled the crank / replaced the key and remounted onto a dead horse... It was exact twin motor you are working on. I went with a new 16hp B&S IC single cylinder motor and still drive it today.
 
That puller will probably work. All you really need is a steering wheel puller. There's bolt holes in the flywheel for removal. It's tightness is a combination of wedgemating and corrosion. It will go back on easily, then just torque the nut down. I wouldn't heat it for fear of melting crankshaft seals. And if you want to check compression, which I doubt it is, the easy way is to spin the motor backwards by hand. When it reaches compression, it should at least try to spin forwards a little rather than just going "poof" and moving past TDC in reverse. This is the method Briggs recommends for their engines. If you get ahold of a tester, anything below 50 or 60 psi is where they really start having problems cranking, but I've gotten them to run at less than that with judicious application of fogging oil and lubricant to the valve guides.
 
catfishblues said:
Yes, and it doesn't take much movement to shut one of these down. I usually find them completely sheared, but I've heard of just a little smearing killing them.
Click to expand...

Yes, while pushmowers are more prone to this (due to spinning blades contacting immoveable objects), even a slight scoring on the alloy keys will will keep it from running, BUT they will still have fire (just out of time). Since you have NO fire, it's worth checking, but likely not the cause...

mbalbritton said:
I have a small puller. maybe 4" deep and up to 6-8" wide. Guessing that ain't wide enough if I have to grab the flywheel. Guessing you had to press it back on , or is there a nut to run it back down with?
Click to expand...

A "steering wheel" type puller is fine, provided you have bolts that are long enough. Your crank should be "short", since it likely doesn't have a pull start (crank was longer on flywheel side for sprag). While I'm sure this will generate some heat...
  • Take off shroud, screen, & large flywheel nut/cup
  • Run a hefty prybar under the flywheel with the bar resting on something substantial like a web or fastener boss (NOT something unsupported like the thin crankcase casting!)
  • Apply a little pressure to raise the crank/flywheel...
  • Then a few controlled whacks with BFH & brass/AL drift on the crank (you're just trying to shock it, NOT drive the crank thru the block!)
  • Flywheel will come off
You just torque the nut back down after checking the key (available everywhere should yours be sheared/questionable)
 
Caver Dave said:
Yes, while pushmowers are more prone to this (due to spinning blades contacting immoveable objects), even a slight scoring on the alloy keys will will keep it from running, BUT they will still have fire (just out of time). Since you have NO fire, it's worth checking, but likely not the cause...



Click to expand...
Dave, he said there was "little to no spark" when holding the plug to ground. I don't know about your experience, but I've never gotten consistent spark when doing the "hold it to ground" test on small motors, even when they start and run fine. I always feel like if you see spark at all, then it's probably good to go in that department.
 
6BangBronk said:
I pulled only one 15-18 years ago? By hanging the flywheel from a large oak limb (chained to the flywheel) and bouncing up and down on the mower front. Used the mower itself as leverage. It still took hours and when it went, so did I to the ground. I remember that early age moment well...
Click to expand...

:lol::lol::lol:

That was worth the entire thread! Thanks!
 
catfishblues said:
Dave, he said there was "little to no spark" when holding the plug to ground. I don't know about your experience, but I've never gotten consistent spark when doing the "hold it to ground" test on small motors, even when they start and run fine. I always feel like if you see spark at all, then it's probably good to go in that department.
Click to expand...

To clarify my "little to no spark" it went from little... to no spark. I have read that holding the plug to ground is not a definitive test for the ignition coil, but it might give you an idea. At this point, I couldn't get any spark the last time I checked it.

I did read that if the ground wire coming off the coil is short circuiting, it can also cause a no run situation. might be worth checking as well. It said to disconnect the wire and try cranking it. if it starts, you won't be able to shut it off with that wire disconnected. Connect it, if it dies, short circuit on that circuit. fairly simple test since there's a disconnect point for that wire front and center on the engine.
 
I got here late it seems. I have a 24hp BS and a coil went weak on me, I discovered that when my 6yo motor dropped an intake pushrod because the rockerbolt fell out! I discovered the coilwire to one cyl. was pinched/damaged badly by design and manufacturing since it was new and it runs better than ever w the new coil. I "fixed" the other one while I was at it, eliminateing the pinching on that one.
 
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