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PM260Z PTO shut off while mowing and now won't start

#1

F

fmorelli

This machine has the Kohler OHV. Motor runs great - rebuilt it two years ago. Rebuilt deck as well, most electronics replaced. Fuel system replaced. Has run well for a good while.

Was mowing last week and PTO shut off about 10 minutes into the mow. Motor and hydraulics continued running fine. Ran the mower back from the field to the house and shut off. PTO is very hot to the touch. Went to restart the mower and would not start. The starter clicks and attempts to turn the motor, but it is as if the motor is being prevented from turning. After everything completely cooled, same result - starter attempts to kick the motor but no advance. Note the mower ran fine after the PTO shut off. Deck spindles/pulleys turn freely.

Battery full charge, PTO checks at 2.5Ω so not shorted. PTO switch seems fine (continuity when raised for engagement). PTO clutch is original. Any ideas?


#2

R

Rivets

Sounds to me you either have a battery which will not take a charge or a charging system which is not working properly. First thing you have to do is have battery load tested at your local mechanic or auto parts store. The battery may read 12.6VDC but will not hold a charge.


#3

F

fmorelli

Rivets said:
Sounds to me you either have a battery which will not take a charge or a charging system which is not working properly. First thing you have to do is have battery load tested at your local mechanic or auto parts store. The battery may read 12.6VDC but will not hold a charge.
Click to expand...
Sorry should have been more clear when I said new electrical system. New battery this spring, as well as new voltage regulator. Battery was also put on a charger, registered full charge 5 minutes after connecting.

The starter kicks hard. The crankshaft attempts to turn (like 1/4") and stops.


#4

M

MParr

Is your PTO clutch locked up?


#5

R

Rivets

Battery chargers may say fully charged, but that will not tell you the condition of the battery. Having it checked is the first thing to do when these symptoms occur.


#6

H

hlw49

Put a 5/8 wrench on the crank shaft bolt and try to turn it by hand. Try to tighten it if you turn it with rotation you can loosen the bolt and it needs to be torqued to the proper torque. Like MParr said your clutch could be locked up.


#7

F

fmorelli

OK here's the story in case it helps someone else.

Mower ran fine, shut down PTO, rode back to the house and shut off. PTO extremely hot to the touch. Once cool, motor which had been running great refused to start. PTO tested 2.5 ohms but would short on a back probe. So PTO was bad. Replaced PTO. Crankshaft locked up, would not turn. Dumped oil, significant copper shimmering in oil. Here's what we figure: crankshaft bearing was letting go, crankshaft got hot enough to roach the PTO (which recall was hot to the touch). Once the bearing cooled it seized. This is why motor ran fine, but then would not start once cold.

New CV742-3023 ordered up and will install next week.


#8

R

Rivets

I would take a second look at what may have caused your problem, because a couple of things don’t add up for me. First, heat rises so for a crankshaft to get hot enough for the heat to travel down through oil, (you said you dumped the oil and I’m assuming it was the proper amount) and into a spinning clutch, then burn out the clutch doesnot compute. Bearing s in oil don’t burnout, so by your description it would have to have been the rod or upper bearing to go. If it got that hot, you should have had oil everywhere, caused by the rubber oil seal failing with that amount of heat. With that ampunt of heat the top seal would go first. Second, if I recall properly a CV740 series engine doesnot have any copper bearings, nor can I remember any copper used inside the engine. You should find out where that “copper“ came from. I’m not saying that PTO’s don’t burn out or engines don’t fail. What I’m saying is your assumptions as to the cause is very hard to accept. If it were me, I would have opened the engine up to verify the cause before ordering a new engine. Might have been repairable, as a new clutch and new engine is an expense that may not be you the payback you expect. Just my opinion, and could very possibly be totally off base due to age, sniffing fumes, and an occasional drink, just don’t want anyone else making the same expenaive assumptions.


#9

F

fmorelli

Rivets said:
I would take a second look at what may have caused your problem, because a couple of things don’t add up for me. First, heat rises so for a crankshaft to get hot enough for the heat to travel down through oil, (you said you dumped the oil and I’m assuming it was the proper amount) and into a spinning clutch, then burn out the clutch doesnot compute. Bearing s in oil don’t burnout, so by your description it would have to have been the rod or upper bearing to go. If it got that hot, you should have had oil everywhere, caused by the rubber oil seal failing with that amount of heat. With that ampunt of heat the top seal would go first. Second, if I recall properly a CV740 series engine doesnot have any copper bearings, nor can I remember any copper used inside the engine. You should find out where that “copper“ came from. I’m not saying that PTO’s don’t burn out or engines don’t fail. What I’m saying is your assumptions as to the cause is very hard to accept. If it were me, I would have opened the engine up to verify the cause before ordering a new engine. Might have been repairable, as a new clutch and new engine is an expense that may not be you the payback you expect. Just my opinion, and could very possibly be totally off base due to age, sniffing fumes, and an occasional drink, just don’t want anyone else making the same expenaive assumptions.
Click to expand...
Thanks for the input, most appreciated. I pulled the motor this morning. Plan to open it up and check. 50 ft lbs of torque on the crankshaft and it would not turn, with no belts on it. Something seized. I'll see what it is today. You are correct heat rises. But it also propagates across material. I'll report back on what I found; agree 100% on others reading later.


#10

H

hlw49

Kinda scanned over the post didn't see what kind of mower this is on. That can make a difference. I recall several years ago the Kohler had a problem with the bottom main bearing due to the electric pto seeking ground and it would wiped the bottom main bearing out. Old model mowers with only one wire (hot wire) to the clutch it could do this. Is this mower that old? if the clutch windings shorted to ground it could this. Before you put a new engine on the mower I would find out why this happened. Would hate to see you ruin a new engine. Some mower manufactures put a diode in the pig tail or the wire before the pig tail. To stop the voltage spikes that a electric clutch can generate.


#11

F

fmorelli

hlw49 said:
Kinda scanned over the post didn't see what kind of mower this is on. That can make a difference. I recall several years ago the Kohler had a problem with the bottom main bearing due to the electric pto seeking ground and it would wiped the bottom main bearing out. Old model mowers with only one wire (hot wire) to the clutch it could do this. Is this mower that old? if the clutch windings shorted to ground it could this. Before you put a new engine on the mower I would find out why this happened. Would hate to see you ruin a new engine. Some mower manufactures put a diode in the pig tail or the wire before the pig tail. To stop the voltage spikes that a electric clutch can generate.
Click to expand...
2005 Gravely PM260Z 992047 first gen production (00101-01499).

Mine does seem to have the diode inline, but I can confirm.


#12

F

fmorelli

Ok ... decided I should dig into the electrical system some before going any further. I could use a second opinion or two on what I'm finding. The summary is that my 2 year old PTO switch seems to not be happy.
First I unplugged the diode and tested with multimeter ... tests as a one-way valve should.

Next I went after the PTO switch. Mine has 5 legs. Let me first post some pictures, then I'll say what I found:

PTO switch.jpeg

plug face.jpg

plug wires.jpg

wiring diagram.jpg


#13

F

fmorelli

Ok here is what I found, using above images. Paper diagrams are from original factory manuals that came with the mower when I bought it. On the PTO switch ... 3-9 works as shown in the diagram - continuity when disengaged. I'm not sure what the deal is with the numbers swapping in the "1 4 7" posts (maybe factory typo) but nonetheless NONE of those posts show continuity, whether the switch is engaged or not.

I provide photos of the wiring harness so we have all the information directly in front of us. What confuses me is the wiring diagram that shows the PTO switch (last photo). It is a 4-wire configuration, but it seems to me the PTO switch physical diagram does not map location-wise to the 4 prongs on the back of the switch. On the other hand the wiring color lines up perfectly, so unless I am reading something wrong I'm going to run with the wiring color on the diagram.

I suppose my question, assuming everything above is on point - if the "1 4 7" leg never shows continuity, what would I expect the mower to do? Thanks all for any insights!


#14

F

fmorelli

Working on reassembly and will provide a full report once I'm done.

When installing the sheave (pulley) for the hydro belt, on the crankshaft, the pulley is asymmetric (taller offset on one side). I've dug through Gravely and Kohler manuals and cannot find anything that confirms the orientation. Is the fat side of that pulley offset toward the engine or toward the PTO clutch? Thanks!


#15

M

MParr

www.gravely.com

Gravely Lawn Mowers | Commercial Lawn Mowers, Commercial Zero Turn Mower, Atlas JSV

Gravely’s high performance commercial lawn mowers, including commercial zero turn mower, walk behind, or stand on lawn mowers in addition to the Atlas JSV UTV.
www.gravely.com www.gravely.com


#16

F

fmorelli

MParr said:
www.gravely.com

Gravely Lawn Mowers | Commercial Lawn Mowers, Commercial Zero Turn Mower, Atlas JSV

Gravely’s high performance commercial lawn mowers, including commercial zero turn mower, walk behind, or stand on lawn mowers in addition to the Atlas JSV UTV.
www.gravely.com www.gravely.com
Click to expand...
Yes I saw the parts diagram. The sheave is raised on both sides - one more than the other. That shows one side so it's a guess which side of the sheave is drawn.


#17

H

hlw49

Put the sheave on the engine and the belt and see how it lines up with the pump pulleys.


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