problem with 20 hp Brigs and stratton 33m677

ok... I have just never had one where trying to start it with starter fluid right after installing a fresh plug did not get it to at least try to start.

Well, drying out the fuel system is cheap, free, and easy to do. And the first thing I always do. Taking the cap off of the fuel tank, and stuffing a clean rag halfway in there and letting it sit in the sun, and wick away that water, also loosen the nut on the bottom of the carb, and let that water dribble out and dry in the sun as well.

you keep assuming there was water in the engine. I do not have any evidence of that.

Yeah, I assume a lot......

Ok, take the kill wire off of the coil, but to shut off, you will need to choke the engine or else pull the plug wire to shut it down. This will eliminate the wiring {except for the coil itself}. Then if you still keep having these intermittent problems, then you have compression and/or fuel to look at. And most fuel problems involve water/crap in the fuel system.

Took my fluke and put negative to engine and touched the Black terminal on the starter solenoid and engine rotated. Bad starter? I replaced it, maybe put old one on and try

You are there with the mower right in front of your face.
We are here with nothing to on but what you tell us.
Wont Start , not trying to start etc etc etc are meaningless.
Rotates at usual speed but wont fire tells us something useful
Rotates then hesistates tells us some thing useful.

While you have a Briggs & Stratton engine , that is only 1/2 the story.
It is fitted to something and that something has a model number which can be used to reveal the wiring diagrams which are very helpful when trying to work out why an engine will not run.
Generally a shut down then no start problem will be in the mowers wiring not the engines wiring.

If the engine rotates then pop an inline spark tester in a new plug and see if you get flashes when the engine rotates.
If not disconnect the cut out wires to the magneto coils and try again.
If you get a spark the second time & not the first then the wiring is the problem.
If the engine does not crank then follow the proceedure below, EXACTLY and let us know what you find.
This is not the only way to do it but it is my way to do it and the individual tests need to be done in the order listed.

Before you start, pull the spark plug & try to rotate the engine by hand.
No use checking the electrics if you have a hydraulic lock, seized engine or jambed belt overloading the stater motor.
Assuming the engine turns freely.

I like to start from the starter motor and go backwards .
Do the following 5 tests, regardless of the results from an or all of them as there can be more than one problem and you want to isolate where the problem lies.
Elimination of individual parts is important so you know by the end, the battery, solenoid & heavy power circuits are all in good order.

1) try to jump the starter motor directly from your car or truck.
Starter turns = starter good

2) do the same directly from the mowers battery
Starter turns = mower battery good
No turn = duff battery, recharge it & try again.

3) check for voltage ( + 12V ) at the solenoid trigger wire with the key in start position
3a) same with ground trigger wire ( 4 wire solenoid ) or body of solenoid ( 3 wire solenoid)
( I like to test V from the battery hot terminal to ground terminal rather than ohms as they give funny readings )

4) leave ground jumper in place ( from step 2 ) & try key start.
Starter turns = power connection good but ground connection suspect ( most common )
Confirm it by trying again, extra ground removed
I run a secondary ground from the grounding bolt to one of the starter mounting bolts & paint over both with liquid electrical tape.

5) Remove the trigger ( thin ) wire / wires from the solenoid.
Ground one & bridge from the hot terminal to the other.
Starter cranks = solenoid good.
Solenoid is not polarity sensitive, BUT THE WIRING IS so make sure you remove the thin control wires.
Note a thinner wire on the hot terminal is not a control wire. It is the main power feed to the mower.


From here on things become very mower dependant as starting circuits are getting changed all the time.
Basically the power goes in a loop from the hot side of the solenoid ( saves wire, no other reason ) through the fuse to the B terminal on the key switch then to the PTO switch then to the parking brake switch then to the solenoid trigger switch , easy peasy after you grow the 3rd arm. Use a test lamp and follow the power.
However a lot of mowers with a 4 pole solenoid, run a secondary ground control circuit to the ground solenoid wire through the lap bars.
Then to stop this interfearing with the normal safety function of the ground kill, it goes to a relay with the ground as the switched connection.
These are a PIA as the + control wire to the relay comes from the power loop above and the ground side of the control comes via the normal cut out functions of the lap bars.
Be very careful because if you have a system like this and accidentally send 12V down the ground loop you can fry the magnetos on some circuits.

Is this the same guy posting on another thread with the same issue ??

Boudreaux In Eunice La. said:

Is this the same guy posting on another thread with the same issue ??

Click to expand...

Yes at this thread http://www.lawnmowerforum.com/showt...-70040-brigs-and-Stratton?p=280445#post280445

I seen him posting on the earlier one saying he posted on the wrong thread Thanks Mon Ami ......

Bad ground.