Troybilt Pony - B&S 17hp Starting Problem

KenH99

Member
Joined
Nov 7, 2019
Threads
1
Messages
13
2013 TroyBilt Pony. Briggs & Stratton model 31c707-3026 G5, 17.5hp. Bought used April '19. Changed oil, replaced spark plug and fuel filter at that time. Ran fine until last week. Used it for about 20 mins, stopped to empty grass catchers and wouldn't re-start, no matter what.

What I've done:

1. Replaced spark plug, although the one from April looked good.
2. Used an ignition/spark tester - saw ZERO spark no matter how I set the tester.
3. Ordered new coil. While waiting for new coil to arrive used a wire wheel to clean rust from flywheel and magnet.
4. Replaced Coil/Magneto. Briggs & Stratton website said the original coil was replaced with a model #595304 coil, that's what I installed.
5. Installed and gapped new coil per instructions.
6. Tried starting the mower. The engine ignited for about 3-4 seconds then shut off and NEVER re-fired.
7. Used ignition tester again. Consistent spark seen at the tester's gap size shown in the pic. I do not know which lines on the tester's Small Engine (SE) section represent an approx .30 gap. NOTE: When I adjust the tester any farther out than pictured the spark becomes intermittent.

Fuel (ethanol-free) is fresh, no water.

Does the tester's spark gap shown in the pic confirm that now the coil is working properly?

Please, what's next?

Thanks, Ken
 

Attachments

Luffydog

Well-Known Member
Joined
Jan 31, 2018
Threads
6
Messages
554
The carb solenoid might be failing. Try to feel or listen for a clicking noise when the key is turned on and off at the carb.
 

Scrubcadet10

Lawn Addict
Top Poster Of Month
Joined
Sep 24, 2017
Threads
111
Messages
1,991
Spray some carb cleaner into the carburetor through the air intake behind the air filter. If it fires then dies you know it's a fuel delivery issue.
Either like Luffy said the solenoid
Does it have a fuel pump or gravity fed?
 

KenH99

Member
Joined
Nov 7, 2019
Threads
1
Messages
13
One step forward, 3 back. Grrrr!

I was checking over stuff before starting the fuel troubleshooting and saw that I had left the wiring harness disconnected after I cleaned it the other day. STUPID! Re-connected it and tried starting. Cranked right up! Cool! Let it run for a few mins and did good. Was elated. Shut it off and put everything back together, engine cover, hood, etc. Restarted and drove it around the backyard w/blades engaged for about 15-20 minutes. Mostly wanted to recharge the battery. Ran fine. Shut down and tried quick restart to seee if battery charged, strong crank and started fine.

Went inside for about 30 minutes and came back to it. Tried to start but NOTHING. Flywheel turned maybe half a revolution then THUNK and stopped. Tried a few more times and same.

Then started smelling GAS, REAL strong. Opened hood and the carb was covered in gas. Wiped it down and more appeared. Looked like it was coming from around the (?) throttle shaft, see pic. NOTE: When I was cleaning everything a few days ago, brushing dirt off the carb w/a paint brush, I found a half piece of what appeared to be washer or spacer coming off that same shaft with the spring. Kinda looked like it was made of foam? It was deteriorated so hard to tell. ALSO, gas was seeping out of the hose (at carb) that feeds gas from carb up to top of engine block.

THEN, I glanced down to left and saw gas RUNNING out of the lower front of the mower, out of the MUFFLER. WTH!

With that, and gas still seeping out of the throttle area, I crimped fuel hose from tank and disconnected it.

1. Why/how did so MUCH gas end up in the engine to run out of the muffler?

2. Does the engine 'thunk' mean anything?

Where do I go from here?

carb-rear.jpgcarb2-washer missing.jpgcarb-muffler.jpg
 

Scrubcadet10

Lawn Addict
Top Poster Of Month
Joined
Sep 24, 2017
Threads
111
Messages
1,991
sounds like the needle and seat in the carburetor has failed. it limits the fuel allowed into the bowl, when it fails. fuel keeps coming in the bowl and goes out any exit. there might be alot of gas in the combustion chamber causing it not to turnover.
there is usually a little piece of material around the throttle shaft to keep dirt out etc.

your crankcase might also be full of gasoline too. do not start it until oil and filter are changed.
 

KenH99

Member
Joined
Nov 7, 2019
Threads
1
Messages
13
sounds like the needle and seat in the carburetor has failed. it limits the fuel allowed into the bowl, when it fails. fuel keeps coming in the bowl and goes out any exit.
How do I confirm and fix that? Rebuild carb? Never did that but if I can find adequate instructions no problem trying.

there might be alot of gas in the combustion chamber causing it not to turnover.

Again, How do I confirm and fix that?

there is usually a little piece of material around the throttle shaft to keep dirt out etc.

your crankcase might also be full of gasoline too. do not start it until oil and filter are changed.

Don't think there is an external oil filter. Didn't see any gas on dipstick but have no problem changing oil.
 

Scrubcadet10

Lawn Addict
Top Poster Of Month
Joined
Sep 24, 2017
Threads
111
Messages
1,991
Yes, either rebuild or replace carb .Okay, I'm just listing the common problems that accompany the needle and seat failing. I have not seen a carburetor flood before that did not have the needle and seat fail.
Take out the spark plug and try to start the engine, if it spins over easy, you may have a valve problem, if it spits out a bunch of gas the chamber was full.
Be sure to smell them oil on the dipstick too. Just to be safe.
The only way for gas to run out the muffler is through the combustion chamber.
If I am thinking right that hose that comes from the top of the block to the carb, it is some sort of vent hose that puts the air back into the intake system. I think it's an EPA deal.
In the first picture, is that black hose coming from the air filter, correct?
 

Scrubcadet10

Lawn Addict
Top Poster Of Month
Joined
Sep 24, 2017
Threads
111
Messages
1,991
https://www.partstree.com/models/31c707-3026-g5-briggs-stratton-vertical-engine/carburetor-kit-carburetor-overhaul-3/
you are going to have to find out if you have a Nikki or Walbro carb. the walbro carb should have LMT stamped in it somewhere, and the NIKKI should say NIKKI on it somwhere.
the overhaul kits are 121 and 121A in the parts list. 121 is for one carb 121A is for another brand.

of course you might can find a cheap chinesium on Scamazon or EvilBay if you want. or a new carb, its your money :wink::biggrin::2cents:

of course if you want to wait and see what anyone else has to say what it might be go right ahead
you wont hurt my feelings by wanting a 2nd opinion
 

bertsmobile1

Lawn Royalty
Joined
Nov 29, 2014
Threads
32
Messages
14,666
No need for self doubt you are quite right.

For Ken's benefit.
Because of idiot EPA regulations the old external drains on carbs have been banned.
So before that you wouls see fuel dripping from the carb & know that the float needle was stuck open.
Now days the drain is INSIDE so the entire contents of the fuel tank can leak out, through the carb into the cylinder, past the rings then fill the sump.
Thus you now have a couple of gallons of waste fuel oil mix that is no good to anyone.
You will need to drain and replace the oil at least twice after fixing the carb.
You will find very detailed picture book instruction for cleaning your carb here https://outdoorpowerinfo.com/repairs/

Verify that the float valve is working by holding the carb upside down and trying to blow through the fuel inlet.
If you have a pressure tester it should hold back 10psi or better.
Then hook it back up but leave the bowl off .
Let the fuel clamp off and hold the float with our hands .
IT MUST cut off the fuel flow before it runs out of movement.
Once you have that sorted, it is change the oil, run the mower for 5 minutes or so then change the oil again + the filter is your mower has one.
While you are playing with the carb & fuel lines, get an inline fuel tap and put it in the fuel line before the first other componant so you can just turn the tap off when you change filters, pumps or carbs.
Next time you mow. check the oil again, if it still smells like fuel then change it again.
 

KenH99

Member
Joined
Nov 7, 2019
Threads
1
Messages
13
Yes, either rebuild or replace carb .Okay, I'm just listing the common problems that accompany the needle and seat failing. I have not seen a carburetor flood before that did not have the needle and seat fail.
Take out the spark plug and try to start the engine, if it spins over easy, you may have a valve problem, if it spits out a bunch of gas the chamber was full.
Be sure to smell them oil on the dipstick too. Just to be safe.
The only way for gas to run out the muffler is through the combustion chamber.
If I am thinking right that hose that comes from the top of the block to the carb, it is some sort of vent hose that puts the air back into the intake system. I think it's an EPA deal.
In the first picture, is that black hose coming from the air filter, correct?
the hose comes from the air filter housing just before it enters the carb.
 
Top