Mower engine wont start

[bvdave]

Common problem when a mower dies while mowing.
Is the blade switch turned off ?
Yes we have all done it.

nope, mower didnt actually even die.. wheels just stopped turning because the belt fell off, I turned it off. but no, the blade is not turned on. (was actually part of my troubleshooting since when I have the key in and turn the blade to "on" I hear a thunkiung, which means power is getting somewhere, but its the only noise the engine will make with the key in it.

about to try the jumper idea now...

 

[bvdave]

One of the big solenoid cables goes directly to the starter. You can touch either end of this cable. In fact, you only need to use ONE of the two cables in a set of jumper cables if you use the battery in the tractor. One end goes to the positive battery terminal and the other end you touch to either end of the starter cable. Be advised: This is going to SPARK! DO NOT clamp the jumper cable on the starter cable; just touch it to see if the engine starts to turn over. We are bypassing everything at this point, just to test the starter.

Batteries put out a lot of amperage! Don't touch the jumper cable to any metal portion of the frame or engine or that will be a spark show and you could get burned. In fact, if you don't have any experience with jumper cables, it's best to let someone who does do this procedure. Would hate to hear that you got hurt trying this.

ok tried this, and it sparked and sounded like it was going to try and turn over, I didnt leave it on for more then half a second however (didnt know if it could damage anything or not so I just did it quick to see the reaction)

so... now what do I do next? does that mean something is funky with the starter? any other troubleshooting to determine specifics?

Thanks again for the help thus far

 

[cpurvis]

Did the engine rotate? You should be able to tell that, and if it does, you're not going to hurt anything by letting it spin for a few seconds. If it does NOT spin, that's when you want to disconnect quickly.

Also, make sure the engine CAN spin before you repeat the process. By that, I mean rotate the crankshaft by hand a turn or two.

 

[bvdave]

heres what happens

 

[cpurvis]

That narrows your "doesn't do anything with the key" problem down to interlock switches, wiring or starter solenoid. All we did was bypass all of those and determined that the engine will indeed "try" to crank when supplied with battery power. To fix that, you've got to find the bad item in the "start" loop.

But, the video shows a very sluggish cranking effort, not nearly enough to reliably start the engine. The causes of this can be numerous, ranging from a bad ground connection to incorrect valve clearances. If you have a voltmeter, you can check the ground connections, circuits and switches in the interlock circuits, one at a time, until you find one that isn't working properly. With that taken care of, the first thing I would check the cheap stuff first--make sure the starter mounting bolts are tight, and check the valve clearances to make sure they are within spec. Most air cooled gas engines have a compression release to aid in starting and can be very sensitive to valve clearance misadjustments.

If you understand what I'm talking about, proceed. If you don't, you might want to get someone to set the valves for you.

If that doesn't get it cranking fast enough to start, then you probably have a bad starter.

 

[bvdave]

from that list.. is any of that related enough to the drive belt or pulley system that something could have happened when changing the pulley out? because before that it started just fine and wasnt sluggish at all.

and I just put in a brand new solenoid before I came to the forum on suggestion from the engine repair shop in the next town, so I guess that leaves us with interlock switches (not sure what those are im afraid) and wiring.. so I guess ill follow some wires and see if I can find anything in the meantime..

 

[cpurvis]

I don't think so, unless the belt/pulley incident could have destroyed some interlock wiring or maybe the belt is too tight and dragging?

 

[bertsmobile1]

There is a heavy load on that engine.
1) remove the spark plug.
If the engine spins really quickly you have a problem with the valves, valve gap ( too big ) , cam or decompressor.

2) if it still turns over slow, use a second jumper to make a ground connection to one of the starter mounting bolts or as near to the starter as your can ( I oft use the oil drain bolt )
Motor spins quickly, = you have a bad ground or many bad grounds, time for the wire brush

3) motor still spins slowly, get under and check that when the brake / clutch is applied you can move the belt around freely and with the brake / clutch off moving the belt should turn the engine over * remove spark plug lead.
Check the belt routing.
It is easy to get it wrong and even easier to miss a belt keeper and have the belt sitting on the keeper & not the pulley. This usually wreckes the belt so if that is the case, get a spare cause the on on there MIGHT not last the whole season.