B&S 12.5hp engine help please

10 years ago

Long story short, paid a guy to go over my 4wheeler, clean carb, fuel system, just get it running right again and I asked him to put in a new switch in my pull behind swisher mower since the key broke off and replace a tire on it. Anyway, 4wheeler is doing great but the mower will not start. They never tried to start it before bringing it back to me.

I included a wiring diagram. It is blowing the fuse in the line that goes from the solenoid back up to the key switch. As soon as you turn the key, you hear the fuse pop, nothing else happens. Engine doesn't try to turn over. I put a new solenoid on it, wired back identical, I don't see any frayed wires anywhere. Everything is grounded correctly. I don't know why it is blowing and I am curious of what that one cable actually does in all of this. I thought about just cutting the fuse out, splicing the cable just to see what happens but thought better of it since I guess it is there for a reason...

Any ideas? I've googled the blowing fuse thing and only thing I have found remotely that might be it other than short somewhere was a bad diode actually up in the engine?

Any help would be appreciated. Thanks.

Matt from Ga

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Comments (4)

bill_kapaun
10 years ago
Most likely they used the wrong switch.
Older switches are wired differently (internally) than newer switches, although they may look IDENTICAL externally.

The BLACK wire to the engine probably has 12V in the ON position.
That SHOULD be grounded when OFF and NC when ON.
It's the kill wire that grounds the coil to kill spark.

On older systems, it supplied 12V to the breaker points/coil.
There's a chance they "fried" the magnetron (coil/armature)

It would be helpful to supply the Briggs MODEL & TYPE numbers so we know exactly WHICH engine you have.
12.5 HP Briggs is about as helpful as saying Chevy.
killerv
Original Author
10 years ago
Model 289707 type 1201-e1

Thanks!

I checked the switch. Looks like the original harness doesn't match up to the new switch. Letters to wires were all mismatched. So I took them out and hooked them up to the switch according to their letters. Still wouldn't crank but wasn't blowing fuse. I did the solenoid bypass thing where you connect the two posts and it started spinning up, then I turned the key and it cranked right up. So that's a first and good I guess. When I try to restart it, it tries to spin up for a second before I turn the key again. If I let it sit for awhile it will start up again without issue. Possibly weak battery? It's been cranking up my 4 wheeler fine.
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walt2002
10 years ago
Why aren't you taking it back?

Walt Conner
killerv
Original Author
10 years ago
because it was one of those buddy deals, guy owed a buddy of mine a favor and my buddy was gonna help try to get everything fixed before hunting season. lesson learned.