B&S 18HP engine won't start

[Mamala Bay]

Originally Posted By: greenaccord02
Quote:
Well in a clutch/brake system one must make a complete stop and depress the clutch/brake to change into gears.


I've driven a few and never had to come to a 'complete stop' to change gears. You just release the clutch and shift while using the momentum. There's no need to come to a stop at all. The smoother the shift the better, especially under load. Ever try shifting your mower into fifth and letting off the clutch?


The clutch/brake system is 'one peddle'..it's a brake and clutch in one. There isn't one peddle for a clutch and another for the brake. If you try to change gears when vehicle is moving the gears will grind, it won't shift into gear...something will break.

 

[greenaccord02]

So when you drive your mower, you really do stop completely before shifting into the next gear?

And I'm well aware of how this system works, I've driven several and drive one every time I visit my parents' to cut their grass.

 

[Mamala Bay]

Originally Posted By: greenaccord02
So when you drive your mower, you really do stop completely before shifting into the next gear?

And I'm well aware of how this system works, I've driven several and drive one every time I visit my parents' to cut their grass.


I think the system you are talking of is not a clutch/brake system. There is brake peddle no clutch peddle but it's not the same. Very similar to say a Ford tractor. It's a single type gear transmission you can't change gears. You set the gear before going in motion. If you want to change gears one needs to stop the tractor and then change into another gear.

 

[greenaccord02]

Maybe I'm mistaken, but I thought we were talking about a belt drive system. I didn't think sears sold gear drive lawn tractors.

 

[Mamala Bay]

Well you need the OP to state his system. I could be wrong, I have no experience with Sears products.

 

[greenaccord02]

Yeah, that would help. Craftsman and Snapper is what most of my experience comes from.

 

[Jerryb]

Gentlemen, I didn't want to start anything here. The model # is 917.273752. I tried to cut and paste the wiring diagram but failed. A pdf diagram is online at sears.com. I checked the seat safety switch and it's OK. I sprayed it and the blade engage switch with WD40. The mower ran fine on Monday. Someone mentioned the PTO switch. I don't know where that is and the wiring diagram and parts list don't mention a PTO switch.

I appreciate you all trying to educate me and look forward to any more comments how this model operates. Thanks

 

[Jerryb]

http://www.managemyhome.com/mmh/answers/Answers.action#l4q121939

Here is the link with a wiring diagram.

 

[Bill Kapaun]

It pretty much HAS to be the seat switch.

Note- just unplugging the connector to the seat switch does NOT disable it!
It has a shorting tab that slides in place and completes the circuit. (grounding connector)

The kill circuit works by grounding the M terminal of the ignition switch.

You can also disconnect the kill wire at the engine to verify. IF the engine now runs after disconnecting that wire, the kill circuit is grounded.

 

[Jerryb]

Thanks for looking at the wiring diagram. I checked the seat safety switch with an ohm meter and it seemed to work. Maybe removing it and cleaning the connectors and spraying with WD40 made things work. What about the switch for the blade engage? What part was that on the diagram?

Thanks

 

[Bill Kapaun]

The blade engage is the attachment clutch.

I'm using the schematic on page 31/56 in this owners manual=
http://www.managemyhome.com/mmh/lis_pdf/OWNM/L0404217.pdf


As you can see, the M (magneto) terminal of the ignition switch goes to the coil. When grounded, it kills the spark.
When the key is OFF, M is grounded, or else M is grounded through the 3 safety switches.
IF you are in the seat, that switch is open, so the other 2 switches can't kill the engine. Out of the seat and if EITHER/BOTH of the other switches is ON (Pedal up or PTO engaged), it will kill the engine.

Where a lot of people get confused, is the seat switch is OPEN when occupied. Pulling the connector plug doesn't open the circuit because of the shorting tab in the plug. That's to prevent seat switches from "accidentally" getting disconnected

Your system is still relatively simple. Some (multiple OPR's) get much nastier to troubleshoot.

Note- It's the BLACK wires in the clutch & PTO switches that are the kill circuit. The WHITE wires are part of the crank circuit.

 

[c3po]

This is what you need to do, on the coil there is a wire going to the coil, it is for all of your safety switches, just disconnect it and the mower should work fine.

I liked what 1 person said, did you tip the mower, maybe a small push mower, but not a 18 H.P. tractor that weighs probably about 250 pounds.