Need to pick the collective's brain, lawn mower issues...

Oneofsix

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Craftsman LT3000
21hp B&S Gold
new battery
Just looking for some confirmation before dropping the cash on a new starter...

So, the issue I'm experiencing is the mower starts to turn over, depending on where it is in the "combustion cycle", for lack of a better term. Seems to get to point point during turning over that the compression is too much to overcome, so it stops. I can bump the starter but it won't go past that point on it's own. I can hand turn the engine past that point and sometimes, its like it can build enough momentum to continue, then it fires right up. Other times not.
I repaired a BUNCH of mouse chewed wiring today, under the cowl that holds the steering column in place between the steering column and the gas tank-suggestions to keep them bitches away appreciated too. I was hoping it was that, but nooooo....
Oh, and I tested a fuel solenoid over near the carb at my BIL's suggestion, it seems to work as it pops out when the key is turned.
Motor spins freely if that solenoid is unplugged or the spark plug is taken out.

go....
 
Check oil level. If the carb float hangs, fuel can get into the crankcase and over fill the engine sump to the point that the starter is strained to spin the engine. Common problem when machines sit over winter with no inline fuel shut off valve.

If oil level is fine and no gas in crankcase, double check that battery terminal connections are tight with no corrosion. Followed by both posts on the starter solenoid, and then the starter positive lug.

If all the above checks out, you could have a bad starter, most outdoor power equipment shops can bench test the starter.

There are other possible issues, but start with the simple things first.
 
This actually started at the end of last season, I usually change the oil before putting it up but I'll check it again.
Cleaned up the terminals when I changed the battery, I'll check the solenoid posts because I didn't pull the boots off to check. Read in another thread here the solenoid shouldn't pull the battery down past 9 volts while cranking, need to check that too.
 
That doesn’t sound like a starter issue. First thought was battery but you said you just replaced it.

My second thought is along the lines of what fullboost suggested. It sounds like it’s having difficulty overcoming compression. This could be caused by a bunch of things.

@Mike Overlay
 
It sounds like it’s having difficulty overcoming compression. This could be caused by a bunch of things.

@Mike Overlay
Exactly my thoughts- especially since I can hand turn it just past the highest compression point and it "might" go on to starting once I hit the key, Sometimes yes, sometimes no.
And if I unplug the fuel solenoid or take out the spark plug, no trouble whatsoever turning over.
Just at my wits end, I was really hoping the wiring harness being chewed to hell was the problem.
bdfdc70864628fa91f4412a6a79174bc.jpg
 
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Hook jumper cables directly to the starter, if it spins normally, its not the starter. Im in st pauls, so not too far if you want me to look at it.

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Exactly my thoughts- especially since I can hand turn it just past the highest compression point and it "might" go on to starting once I hit the key, Sometimes yes, sometimes no.
And if I unplug the fuel solenoid or take out the spark plug, no trouble whatsoever turning over.
Just at my wits end, I was really hoping the wiring harness being chewed to hell was the problem.
bdfdc70864628fa91f4412a6a79174bc.jpg
If the issue started last season before the wiring damage, it could be the compression release on the camshaft is broken, putting a higher load on the starter. Some of the single cylinder Briggs motors have a compression release with a small spring that can break.
The engine model number will be stamped on the valve cover.
Model:
Type:
Code:

Also check the bendix drive on the starter. If yours is plastic, the teeth on the gear can round off.
 
The wires look to be the problem, cut the damaged wires out and splice new.
 
The wires look to be the problem, cut the damaged wires out and splice new.
Already spent most of the afternoon doing just that, popped the 20amp fuse because I forgot to disco the battery. Checked the battery before the fuse, 12.8 amps.
 
If the issue started last season before the wiring damage, it could be the compression release on the camshaft is broken, putting a higher load on the starter. Some of the single cylinder Briggs motors have a compression release with a small spring that can break.
The engine model number will be stamped on the valve cover.
Model:
Type:
Code:

Also check the bendix drive on the starter. If yours is plastic, the teeth on the gear can round off.



Model: 331877
Type: 1371 81
Code: 100611ZD
 
From my experience with similar B&S engines, you probably need to adjust the valves especially the exhaust side. When they get loose, it's hard for the built in compression release to work
 
If the battery tests good with a load-tester, I would try jumper cables directly to the starter. If it still turns slowly - replace starter.
If it turns better with jumpers, the mice or corrosion have gotten to the wires. Clean all terminals and ground cables at both ends.
Replace wires that can't carry the load anymore.

As far as the mouse is concerned ... how about a hungry cat, or a black snake ... maybe a falcon?
 
Already spent most of the afternoon doing just that, popped the 20amp fuse because I forgot to disco the battery. Checked the battery before the fuse, 12.8 amps.
Check your amps at the starter. As another advised jump the starter with a certain power source, if it turns the motor you need to review your power source, supply lines, relays and switches, good luck.
 
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Even new batterys can be bad. You need to get the battery load tested. It can have plenty of volts on a meter but not have enough amperage to turn it over. If not that then a bad connection on the main cables or the soleniod contacts are burnt up in that order to check.
 
Sounds to be a voltage issue. Check connections at battery and starter and check grounds. Wouldn't hurt to load test the damaged/repaired circuits.
 
Check the starter solenoid. I had an old mower with the same symptoms and the solenoid was bad. If I jumped out the solenoid with a piece of wire, the motor spun and fired easily. But if I used the key, slow crank and no fire.
 
As @Ikarus1 suggested above adjust your valves.
They should be around 6 and 9 thousands when you check yours they will be in the 13 range. Look for how tos on the you tube also look up specs online. It's not a hard job I've probably done a hundred of them. You may need new valve cover gaskets.

Quit overamping that starter or you will need a new one.
 
The reason why I think it's the valves is because the starter runs til it gets to the compression stroke. If it were electrical and has enough voltage to spin the engine it should be enough to start it. If the starter just clicked the solenoid then I would check wiring/battery terminals
 
As @Ikarus1 suggested above adjust your valves.
They should be around 6 and 9 thousands when you check yours they will be in the 13 range. Look for how tos on the you tube also look up specs online. It's not a hard job I've probably done a hundred of them. You may need new valve cover gaskets.

Quit overamping that starter or you will need a new one.
I can barely fit. 006 on the exhaust side,.007 barely fit on the intake side.
Checked to make sure I was at TDC too, per the YT video.

Strange happenings, so another video showed how to "bypass" the compression spring/ valve- essentially just completely choking it. I did that before checking the valves, then it started turning over completely but wouldn't catch-but not every time.
When I took the plug out it was wet so I figured it must have just flooded.

The valve vid also showed to check the starter lug for looseness, it was very loose once I took off the wire from the solenoid. So that's been tightened up now too.
Gonna check plug gap before putting it back together.

Sent from notthedroidyourelookingfor
 
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So, watched the YT video again that explained the process for checking the valve clearance- realized that while rotating the motor to get to TDC, the intake valve should have bumped a little going over the compression release- it didn't.
So, planning to clear my work bench in the barn to tear down the motor to replace the camshaft.
Thanks for all the input everyone.


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So, watched the YT video again that explained the process for checking the valve clearance- realized that while rotating the motor to get to TDC, the intake valve should have bumped a little going over the compression release- it didn't.
So, planning to clear my work bench in the barn to tear down the motor to replace the camshaft.
Thanks for all the input everyone.


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Yea, I didn't think to mention that I've only ever had that happen a couple times, glad you got it figured out.
 
Well, just dammit....


Got all the parts delivered Thursday, got everything back together today.
Being somewhat limited physically, I thought getting the motor back together and installed back on the chassis would be a major accomplishment for today. Did that.
Connecting all the wires, etc I got down to the last items- putting the hood on and reconnect the battery, fill it with oil and give it a crank.

That's right when I smelled the gas. Pouring out of the top of the carb. I fiddled with it for a bit, trying to see exactly where it was coming from.
Pinched off the supply line, started taking the cowl off again and heard gurgling...crap.

Sent from notthedroidyourelookingfor
 
Luckily I hadn't filled it with oil yet, so I dropped the drain tube but nothing came out. I figure good so far.
Pulled the intake manifold off and more gas poured out-shit.
Stuffed some rags into the intake, the looked with a flashlight and seems to be no more gas.

No, I didn't remove the carb because of the fiddly damn linkages, in hindsight I should have. Just a stuck float or something ?
At the very least I think I should put some oil in, spin it by hand a few times and dump that oil.


What say the camp? Next step?

Sent from notthedroidyourelookingfor
 
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Hmmm, may have dodged a bullet- took the carb apart after checking the YouTubes and seems the needle popped loose from the float when I was maneuvering the motor around on the bench.
Clipped it back in place and connected the fuel line. So far no leaks. Going to pinch off the line again and head in for some dinner. I'll see what might be in the morning. If all is dry, maybe I can finally cut the yard tomorrow.
It's getting sporty around here walking through the high grass, Mr Noshoulders could be anywhere.

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