Lawn mower PTO shuts down engine.

[richdell]

I swapped a 670 Predator engine into a John Deere zero turn mower. It starts and runs well, but when I activate the electric PTO, the engine shuts down like turning off the key, even with the belt off. I did all the standard checking of switches etc.with no success. Now it gets weird! I disconnected the plug from tractor to PTO clutch and connected a 12v jump box to just the clutch. I started the engine, applied power to the clutch and the engine shut off just like before. I literally have no clue what to do now. One thing I noticed was that the shaft coming out of the engine is a magnet. Any ideas?

 

[James]

Check you are sat on the seat and the seat safety switch is working correctly.

 

[brianmoooore]

Check you are sat on the seat and the seat safety switch is working correctly.

It would be an unusual machine that hadn't had that annoying feature long since disabled!

 

[richdell]

Check you are sat on the seat and the seat safety switch is working correctly.

The clutch is not connected to the tractor's electrical system in any way, I applied power from a separate battery. The safety switches are not in the picture.

 

[brianmoooore]

Check out anything that moves when the PTO is engaged to check it isn't fouling any wiring

 

[richdell]

Okay, here's the skinny. When I installed the Predator in the John Deere, I turned the PTO clutch around to allow the belts to line up. The magnetic hub is close to the engine and is shutting the engine down. (no idea why) I have some room to put something to block the magnetism, but I have to find out what works. It's either that or extend the engine shaft about 2 inches, but that's scary!! Thanks for the suggestions.

 

[brianmoooore]

Just looked up what a Predator 670 is, and it's a V twin 4 stroke petrol engine.
There's nothing inherent about a magnetic field that will stop a 4 stroke petrol engine running - if it has compression, fuel mixture and spark, then it will run.
So what are the possibilities? Magnetic field keeping a valve open or closed. Magnetic field keeping the float chamber valve closed. Magnetic field interfering with the ignition pulse.
What's missing? Spark, compression or fuel?

Drawn to this question since I've just replaced a very expensive magnetic clutch in my own mower.

 

[richdell]

I found a good tutorial on building a simple magnetic shield on YouTube so that's next.

 

[James]

Worth checking that you have a good connection between m/c frame and engine.
If you have a poor ground connection it could be failing with the current draw of the clutch.

 

[richdell]

The connection is good.

 

[Avo Mk8]

I was intrigued when this thread was first posted, and ended up looking for circuits of John Deere zero turn mowers!
I came across the diagram below (suspecting it's probably not the right model), but I was interested in the relative complexity and the presence of the "switched power" rail.
I was originally going to suggest monitoring that rail to see if it goes down when the mysterious stopping occurrs.

But having read the latest, I guess the 'magneto stop' relay (if there is one!) might be responding to the clutch magnetic field, though I didn't think relays are normally that susceptible to external magnetic fields.

Could it still be an electrical issue somehow?

 

[richdell]

I connected a jumper between the clutch frame and the chassis ground, started the engine, engaged the PTO and it kept running! I then removed the jumper and it continued to work correctly. I am going to connect a wire just in case, but I think my problem is solved. Thanks for your suggestions!

 

[Rockingit]

This thread reminds me….always planned to build a V8 lawnmower. Ride on, naturally, with electrically driven cutter deck via 3ph alternator. Unlikely to pass any safety inspection, ever.

I fear for my retirement……