Mower will not restart unless one plug wire is off

[MichiganGT5000]

Hello everyone.

I've had an early 2000's Craftsman GT5000 since new. It is the 24 HP V-Twin.

There have been many problems and each one I repaired myself.

This spring I changed out the fuel pump and thought maybe this year was the one where it would run the whole season without problems. Nope.

Today:

Backed it out of storage shed under own power. Shut down, closed shed door. Drove to second garage on property to fill up on fuel. Checked oil. Down a little, added maybe a 1/3 of a cup.
Got on, engine would not turn over. Oh. Engine must have reversed on shutdown. Happens every dozen or so times. Rocked back and forth, nothing. Pushed up a hill and put in second gear (manual) and rocked it again. Finally the engine began turning and then cranked freely. Pulled full choke. No fire. Starter fluid and cranked. Nothing.

Pushed into garage and took off the right side (near fuel filter) plug wire. Put on a digital meter with the dc volts setting on max and the red lead to the spark plug wire and the ground wedged to the chassis just behind the fuel pump.

Turned key looking for voltage and it was there, kept cranking to get a value and the engine started! What?

It sat there and ran with the meter connected but as soon as I pulled the meter leads off it shut down.

I crimped the spark plug wire tighter to get a better grip on the plug and reinstalled everything. No start.

With the plug out and connected to the plug wire and next to the starter it shows spark and even jumps to the starter body from the body of the plug.

I verified a second time that it runs with the meter in series with that cylinder and a gas oil mixture is pooling under the exhaust.

Did I overfill the oil and hit a sensor of some kind? The dip stick is well within the full hash mark area and does not show over filling.

Stumped to say the least.

 

[chance123]

Hello everyone.

I've had an early 2000's Craftsman GT5000 since new. It is the 24 HP V-Twin.

There have been many problems and each one I repaired myself.

This spring I changed out the fuel pump and thought maybe this year was the one where it would run the whole season without problems. Nope.

Today:

Backed it out of storage shed under own power. Shut down, closed shed door. Drove to second garage on property to fill up on fuel. Checked oil. Down a little, added maybe a 1/3 of a cup.
Got on, engine would not turn over. Oh. Engine must have reversed on shutdown. Happens every dozen or so times. Rocked back and forth, nothing. Pushed up a hill and put in second gear (manual) and rocked it again. Finally the engine began turning and then cranked freely. Pulled full choke. No fire. Starter fluid and cranked. Nothing.

Pushed into garage and took off the right side (near fuel filter) plug wire. Put on a digital meter with the dc volts setting on max and the red lead to the spark plug wire and the ground wedged to the chassis just behind the fuel pump.

Turned key looking for voltage and it was there, kept cranking to get a value and the engine started! What?

It sat there and ran with the meter connected but as soon as I pulled the meter leads off it shut down.

I crimped the spark plug wire tighter to get a better grip on the plug and reinstalled everything. No start.

With the plug out and connected to the plug wire and next to the starter it shows spark and even jumps to the starter body from the body of the plug.

I verified a second time that it runs with the meter in series with that cylinder and a gas oil mixture is pooling under the exhaust.

Did I overfill the oil and hit a sensor of some kind? The dip stick is well within the full hash mark area and does not show over filling.

Stumped to say the least.

Is that non running cylinder's spark plug wet?
I would try to remove the kill wire from the coil that goes to the cylinder that you removed the plug wire from and put that plug wire back on and see if it runs on both cylinders.
Also do a compression check on that non running cylinder.

 

[Carscw]

I bet it will all so run if you ground the plug at the plug opening. I have one that won't start with both plugs in. Take one out and ground it at the opening and will run all day.

(( racing is the only sport that you need two balls ))

 

[MichiganGT5000]

Thanks for both of your responses! Yes the plug is wet. I did not know there was an auto kill wire and have no idea where to look for it.

As for running a ground wire from the plug I am not sure how you would go about it unless you are talking about a wire that is set in the seat section of the plug hole and then run to a bolt on the block somewhere?

As a side note, I have had to run mower with part choke when there is no load on the engine for years. No amount of fiddling or tuning has changed that requirement. Many times it backfires while traveling downhill at in a higher gear with the blades turning. I've always blamed it on the carb design, maybe it has been an electrical issue that was degrading all along.

 

[Carscw]

When I say ground the plug

Take plug out and hook it back up to the plug wire and lay the plug on the engine at the plug hole

(( racing is the only sport that you need two balls ))

 

[MichiganGT5000]

I tried hooking up the plug to the wire and hanging it and the mower would not start like it would with the meter in the same configuration. The fact that the metal base of the plug can be seen arcing toward the chassis along with the arc in the gap leads me to believe a bad spark plug. I have no proof, just a guess.

How do I go about finding this kill wire that may or not be the culprit for that cylinder? It seems to me it might be in the same circuit as the reverse lockout on the ignition switch since it kills the engine when reverse is selected in normal mode.

 

[Carscw]

I am with you it's a bad plug

(( racing is the only sport that you need two balls ))

 

[MichiganGT5000]

Fixed!!!

It was the spark plug. Woke up sick from a cold and asked the Wife to get a new plug from autozone on or back from work. She picked one up for $2 and set it next to our bedside table. Fed me dinner and propped me up with pillows to watch deadliest catch on the dvr. Once she was in the bath I sneaked down to the garage and popped that baby in and promptly sat in a seat full of rainwater! Turned the key and pulled the choke and she roared to life on the second revolution. Scooted upstairs and ditched the wet sweatpants and slid into bed as she was getting out of the bath. "So I heard you got the mower running."

Wives and Girlfriends miss NOTHING.

Thanks everyone! BTW the mylawnmowerforum site sucks. It took all day to get registered and then no one seemed to want to help. I will definitely refer this forum to all my lawn mowing neighbors.