Mower dies when engaging blades

[Findthehumorinthings]

This is a Scotts by John Deere.

Things done and checked:
1. PTO: pulled pto off my other mower and switched out. Same behavior using known working pto at full throttle.
2. Compression check: one cylinder at 138 lbs and the other at 130lbs.
3. Spark: Pulled each spark plug wire while running. Strong spark on both observed jumping from wire to engine body.
4. Deck: pulled belt off pto. Engaged pto running the motor. Pto engages fine. Put belt back on pto. Engage pto at full throttle. Motor dies.
5. Hook yard trailer filled with dirt to mower. Drive it all over the yard, including inclines. Pulls like my other mower.

I’m totally stumped. It’s like something binds that I cannot detect using inspection techniques.

 

[Bertrrr]

Is there a deck spindle binding up or a bad bearing somewhere ?

 

[Findthehumorinthings]

Is there a deck spindle binding up or a bad bearing somewhere ?

I put a v-belt pulley on a drill motor and ran the deck. The small cordless drill was running the deck, albeit at relatively low rpm’s. The deck doesn’t ‘seem’ to be binding.

Is there any correlation between stator output and reduced engine power? I have a new battery on the mower. Just trying to think of anything that reduces power under load.

 

[Bertrrr]

I've never seen this but if you can spin your deck by hand - I would spin each one individually and see how it sounds and feels - you can tell if one is dragging or not. But having said that and you're confident there is nothing binding there, pull your PTO wires off and run a separate 12vt wire to it without going through the switch - let it run at full throttle and then touch hit it with 12 volts from the battery and see what happens just to eliminate the switch assembly . I guess it's possible the switching assembly could be causing this but can't imagine how.

 

[StarTech]

Model number would help but it might the reverse cutout switch stuck in reverse mode or short in the wiring to the switch.

 

[Findthehumorinthings]

Model number would help but it might the reverse cutout switch stuck in reverse mode or short in the wiring to the switch.

Thx for the suggestion. To eliminate a switch issue and the pto itself, I pulled the deck belt off the pto, ran the mower, engaged the pto, and it ran fine. Specifically when the deck belt is on the pto it dies when the pto is engaged. Hand checked the deck and pulled it with a hand drill with a vbelt pulley. Runs the deck fine, albeit at low rpm.

 

[Findthehumorinthings]

Going to try the other suggestion to feed a separate 12v to the pto from an external battery.

Btw, regarding model info: This is a Scott’s 2048. Original motor threw a rod. I have a 22hp out of an LA145 in it.

 

[PTmowerMech]

Does it bogged down and die? Or die's like you turned the key off?

To make sure it's not being drugged down by something on the belt (pulley, belt guide, etc etc) pull the pto and push it in pretty quick like. Then very quickly before belt stops turning, pull the pto again. if it still dies, then you might check your alternator output. If it's fine, you may have something sucking too much juice somewhere else.

 

[bertsmobile1]

Dies like you turn it off or dies like it runs out of fuel ?
If the wiring / battery is not good & the PTO is drawing too much current or has a short then the fuel solenoid on the carb will shut off .

 

[Findthehumorinthings]

I tried the recommendation to use an external 12v source for the Pto. Mower runs the deck fine.
Appears to be a safety switch.
So one by one I’m bypassing each switch.
- shorted reverse switch. Side effect is the relay buzzing.
- bypass the seat switch by sliding a piece of plastic between the middle pins.
- shorted the switch on the side of the hydro
- checked the pro switch for off and on across all 3 sets of pins.
- disabled the fuel bowl cutoff and pulled that wire.

The key wire that changes when the motor cuts off is a black wire to the motor. I think that wire is the ground out for the spark coils and one wire to the fuel bowl cutoff.
When I check that wire to ground, it’s direct to ground with the ignition off, open with the ignition in the run position. And goes back to not quite totally short (small amt of resistance) to ground with the pro switch pulled up.