Export thread

Hello,

I inherited a 1999 Murray 30" Rear Engine mower with a Briggs & Stratton Model #: 28B707 engine. Ever since the beginning the mower does not shut off when the switch is turned to the off position. I have been choking the carburetor to stall the motor to turn it off. Now I'd like to re-wire it correctly so it shuts off when turned to the off position. I am not famiiar with electrical work or lawn riding lawn mowers. I consider myself a handy person and have rebuilt the carburetor in the past for the mower.

I am attaching two pictures of the switch with the harness and the switch itself. It seems the two yellow wires have been cut and electric tape put on the ends. Can anyone tell me how I can wire the switch to shut off?

Those wires are the circuit to shut it off. Why they are cut is hard to say. Likely someone trying to compensate for a bad safety switch.

To get it working at least at the switch, you need to hook the double wires to the terminal on the ignition coil, as it grounds out the ignition to shut it down.
However, you must be careful not to send any voltage to your coil, as that will damage it badly.

i would get a multimeter, set to continuity (beep, if it has it) and see which terminal is Grounded to frame when in the off position.

That switch, the G post is grounded to the outer metal of the switch, and that wire should go to the frame. The M terminal post goes to the kill post on the coil. But yes, one should check for stray voltage, as that will destroy the coil.

Fish said:

That switch, the G post is grounded to the outer metal of the switch, and that wire should go to the frame. The M terminal post goes to the kill post on the coil. But yes, one should check for stray voltage, as that will destroy the coil.

Click to expand...

Thank you all for assisting me. So I should check that the wire for the G post grounds to the frame? I can check this by putting the switch to the off position and checking continuity using a multimeter. The two yellow wires for the M post should be a single wire going to the kill post on the ignition coil? Is that correct.

This is the schematic for a Murray tractor rider from around 1988. Maybe it's close enough to help or it may be the exact .

I'd like to see you kill it with the electric system rather than the choke.

If this is the correct schematic, then you have an electric pto, so following the diagram becomes more necessary, as one of those yellow wires goes to a circuit for the pto switch. One of them goes to the terminal on the coil, and the other one goes through a bunch of safety switches.

Fish said:

If this is the correct schematic, then you have an electric pto, so following the diagram becomes more necessary, as one of those yellow wires goes to a circuit for the pto switch. One of them goes to the terminal on the coil, and the other one goes through a bunch of safety switches.

Click to expand...

Here is the correct electrical diagram for the riding lawn mower. I've highlighted two limit switches that are not present on my mower. My thought was to bypass them all together.

It doesn't show the kill circuit. What is the model number of the tractor/mower itself?

Fish said:

It doesn't show the kill circuit. What is the model number of the tractor/mower itself?

Click to expand...

1999 Murray 30 inch Rear Engine Mower (30500x92A). I think the kill circuit is the yellow wire to the engine. I think it is intended to illustrate the kill post on the ignition coil. The electric diagram is from JacksSmallEngines.com.

Fish said:

It doesn't show the kill circuit. What is the model number of the tractor/mower itself?

Click to expand...

The circuit is in plain sight in post #9...

StarTech said:

The circuit is in plain sight in post #9..

Click to expand...

I see it now,

StarTech said:

The circuit is in plain sight in post #9...

Click to expand...

The wire snuck in the back door. Murrays are sneaky.

So the remaining question I have is, will it be okay to bypass the 2 limit switches noted in the electric diagram from post #9 since the previous owner removed them entirely?

fixit_joe said:

So the remaining question I have is, will it be okay to bypass the 2 limit switches noted in the electric diagram from post #9 since the previous owner removed them entirely?

Click to expand...

I would just wire the thing directly to the kill terminal, but we are not allowed to say it.

If the mower is starting don't worry about the two safety switches. Per the wiring diagram posted they are for the starter circuit and have 12 VDC on them which if wired to the ignition coil will short it out. Apparently someone has already bypassed them. The only safety switch involved in the kill circuit other the ignition switch is the seat switch per the wiring diagram posted.

so to consolodate it
The yellow wire is the kill wire and it goes to ground to stop the engine
check that the key switch connects the yellow & black wires ( M & G terminals ) in the off position
If it does that then check that grounding the yellow wire kills the engine and there is continuity between the G pin on the key switch & ground .
If grounding the yellow wire does not stop the engine check that it is connected to the magneto.
The kill switches are the key switch & the seat switch which are parallel circuits so wither lifting your bum or turning off the switch should ground the magneto & stop the engine

bertsmobile1 said:

so to consolodate it
The yellow wire is the kill wire and it goes to ground to stop the engine
check that the key switch connects the yellow & black wires ( M & G terminals ) in the off position
If it does that then check that grounding the yellow wire kills the engine and there is continuity between the G pin on the key switch & ground .
If grounding the yellow wire does not stop the engine check that it is connected to the magneto.
The kill switches are the key switch & the seat switch which are parallel circuits so wither lifting your bum or turning off the switch should ground the magneto & stop the engine

Click to expand...

My opinion ,along with other posters here, is to never bypass the safety switches because that's what they are for-safety. When I bought my CZ42175,the seat kill switch was disabled. In the unlikely event I turn my mower over, I want my mower to shut off.
The same with the "no start in gear" switches on the steer levers. Engine starts with the drive levers in motion position is never good.

These schematics seem to differ. With Key ON check to see if there is voltage at the Yellow wire. If NOT, connect them to Ground. One appears to be to the seat occupied switch the other to coil ? Start engine and see if it will turn Off.

I took the engine cover off of the engine and i traced the terminal wire for the ignition coil is connected to the frame of the engine (see picture). This makes sense why the engine switch does not shut off the engine when in the off position. One more question, what type of wire can I use to re-route the terminal wire for the ignition coil - solid brass wire like shown in picture or can I use a braided electrical wire?

fixit_joe said:

I took the engine cover off of the engine and i traced the terminal wire for the ignition coil is connected to the frame of the engine (see picture). This makes sense why the engine switch does not shut off the engine when in the off position. One more question, what type of wire can I use to re-route the terminal wire for the ignition coil - solid brass wire like shown in picture or can I use a braided electrical wire?

View attachment 59293

Click to expand...

You should use stranded automotive wire,16 to 20 gauge. This kill switch wire doesn't carry much current. Solid copper wire has no use on anything that has any vibration to it. The shaking,even a little will fatigue the wire ,leading to breakage and circuit failure.

SamB said:

You should use stranded automotive wire,16 to 20 gauge. This kill switch wire doesn't carry much current. Solid copper wire has no use on anything that has any vibration to it. The shaking,even a little will fatigue the wire ,leading to breakage and circuit failure.

Click to expand...

Thank you for answering. I am set to finally get the switch to turn off the motor after having to flood the carburetor for over 7 years. Thanks to all!

Note: Your choke engagement linkage is incorrectly installed.

StarTech said:

Note: Your choke engagement linkage is incorrectly installed.

Click to expand...

All my Briggs linkages look like this and there is no separate choke cable. When the throttle lever is moved to full wide open,the part of the linkage that is unseen in the posted pic,moves to push that loop of wire to the left (in the posted pic) to close the choke butterfly. Moving the throttle lever back just a bit opens the choke butterfly and the throttle butterfly is still fully open.

All my Briggs linkages look like this and there is no separate choke cable. When the throttle lever is moved to full wide open,the part of the linkage that is unseen in the posted pic,moves to push that loop of wire to the left (in the posted pic) to close the choke butterfly. Moving the throttle lever back just a bit opens the choke butterfly and the throttle butterfly is still fully open.

Click to expand...

Then they all are installed incorrectly as both sides of the double section goes through the slot, not just one side. This does two things. One is to stabilize the linkage, Two to make easy to remove the carburetor and the linkage as one unit. The way it is in the posted image puts stress on the plastic choke lever.

StarTech said:

Then they all are installed incorrectly as both sides of the double section goes through the slot, not just one side. This does two things. One is to stabilize the linkage, Two to make easy to remove the carburetor and the linkage as one unit. The way it is in the posted image puts stress on the plastic choke lever.

Click to expand...

Good catch,StarTech!
I need to re look at the OP's pic. My mistake. Of course both sides of the loop go through the slot. I was concentrating on the Ground wire not the choke linkage :-(ashamed)

SamB said:

I need to re look at the OP's pic. My mistake. Of course both sides of the loop go through the slot. (ashamed)

Click to expand...

Sam it easy to miss if you are not careful. I see it a lot in the shop here where another tech just slapped the carburetor on.