I swapped a Predator 670 engine into a John Deere 757 zero turn. I started the engine, engaged the pto, cut some grass, but the engine was smoking very badly, so I removed the engine, exchanged it and the new one runs great but when I turn on the mower it dies. The belts are free, the clutch shows about 2 ohms, no grounds. When I disconnect the wire plug to the clutch the engine continues to run when I turn the pto on. The battery voltage drops about 1 volt when I hit the starter. Oddly, the battery voltage does not drop even though the pto starts to turn the belts a little before the engines quits. I attached the wiring diagram form the manual if that helps. I am at my wit's end!
Fuddyduddy1952
Elite Member
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Here's how I would troubleshoot it. The PTO clutch has two leads, black and blue wires. I'd unplug it. Then (not running of course) use two clip leads, one to ground, other battery +positive. Just for a second or two and you should hear it click (engage) each time it gets power. Now I'd start mower and connect again. Caution! Of course you have to be careful doing this! Harbor Freight sells a clip lead set...you may want to make long ones so you can try it while in seat.
If this works and engine doesn't cut off you know clutch and drive system is fine.
Then looking at diagram next is PTO relay. It gets power from PTO switch, however, all those safety switches like brake, seat and control lever switches must be good and engaged to work otherwise motor cuts off.
My guess is it's one of the safety switches either bad or not engaging as it should.
If this works and engine doesn't cut off you know clutch and drive system is fine.
Then looking at diagram next is PTO relay. It gets power from PTO switch, however, all those safety switches like brake, seat and control lever switches must be good and engaged to work otherwise motor cuts off.
My guess is it's one of the safety switches either bad or not engaging as it should.
WranglerX
Super Member
As Fuddyduddy says, check all the switches....
I have done all the checks suggested here as well as other internet sources, with no answers. Today I powered the clutch on with a separate battery, (not connected to the tractor) and it still shut down the engine. The clutch spun until the engine stopped. (belt was off) This is my son's mower, so I can't scrap it!
oldnslo
Super Member
Is the engine stopping like turned the key off or lugging and dying?
From what you describing with separate battery I suspect lugging and dying. If yes to the lugging then you have other issues like mechanical binding in clutch or deck if belt is connected. Possibly bearing going bad in clutch, etc.
If deck is connected could be engine running a little lean or governor is a little sluggish on response, etc.
From what you describing with separate battery I suspect lugging and dying. If yes to the lugging then you have other issues like mechanical binding in clutch or deck if belt is connected. Possibly bearing going bad in clutch, etc.
If deck is connected could be engine running a little lean or governor is a little sluggish on response, etc.
Richard001
Veteran Member
In post #6 the OP said that the belt to the deck was not in place.
Richard001
Veteran Member
When you applied power to the clutch from a separate battery, was the connector that goes to the clutch still connected ?
No, it was not connected the jump box was completely isolated.
