PT 1850 mower stopped suddenly.

[BWSwamper]

Mowing today and the PT1850 mower stopped suddenly. It just spun down and stopped.

Blades and hydraulic mower motor turn freely.

At first I suspected PTO electric issue, but then noticed slight to moderate engine rpm drop when PTO switch was turned on.

No significant new leaks.

Any suggestions?

 

[ponytug]

When you switch the PTO ON/OFF,

• Can you see a change in the fluid flow in the tank?
• Does the hose to the mower flex?
• Can you feel the mower motor spin?

My guess is that the motor to mower coupling broke. Which mower are you running?

All the best,

Peter

 

[BWSwamper]

Thanks. This is with the 7 ft. three spindle Brush mower.

I'll check those all those items tomorrow.

I thought I saw the mower motor sitting still, but i was really just looking at the coupling. If the finger coupling broke I could have missed the top spinning.

Could you clarify what you mean by the mower hose flexing? These are pretty large diameter and don't pulse much when engaging normally.

The broken coupling fits with the timing of the event. I was mowing along a bank in a pasture with 2 1/2- 3 ft. Fescue and had just knicked a root.

 

[agjones]

If the coupling looks OK externally... Could be the set screw/key on the coupler.

 

[MossRoad]

Usually when I flick on my PTO switch, even at low engine rpm, the hoses to the mower will flex.

That's a good test to see of fluid is getting to the hoses.

 

[MossRoad]

If the covers are still on the belt and pulleys, look for a broken belt, too.

 

[BWSwamper]

Thanks guys. I'm going to be investigating all those issues this afternoon. I'll report back.

 

[BWSwamper]

Upper and lower halves of lovejoy coupler both fixed to their respective shafts. Hydraulic mower motor shaft can be rotated by turning the coupling.

Mower belt intact and all spindles turning easily simultaneously by moving belt by hand.

Rpm drops slightly when pto engaged.

3/4 inch main mower lines don't pulse or flex when pto is engaged, but I don't remember noticing much of that before as they are pretty stff and lay over the top frame mount of the mower.

 

[agjones]

Stuck relief valve?

 

[BWSwamper]

That was my next question. That was the only thing left on the Service FAQs for PTO not working. ("Trash in relief valve"). Except for a bad pto pump, but this pto pump hasn't made any noise and isn't leaking.

Where is the relief valve in question located, and how would one clean it out?

 

[BWSwamper]

If I've got things straight, these are the two relief valves on the top of the PTO control valve assembly on the right side of the chasis as one faces the front of the machine.

I guess the cleaning procedure is just remove them clean them out with something like WD40 and reinstall.

Is it okay to use starting fluid as a solvent in this case?

 

[ponytug]

Any non-aqueous solvent should be fine. Brake cleaner would be ideal because it is more forceful, and you can blast any trapped trash out of the relief valve/housing. Check the spring on disassembly to make sure that it didn't crack. (Rare, but it happens)

I hope that fixes it for you.

All the best,

Peter

 

[agjones]

The couple times I had this issue on different equipment, I never saw the suspect. But checking the relief valve and cleaning it solved the problem. So don't necessarily expect a gotcha moment.

+1 on the brake fluid. It's gone by the time you reassemble.

 

[woodlandfarms]

If you aren’t bogging the engine it’s probably a relief valve. My engine will pull through but you do notice a drag when the pto solenoid is engaged.

 

[BWSwamper]

Turns out the problem was that the PTO solenoid/plunger was bad. It was still making a clicking sound when energized, but apparently the plunger got hung up and wasn't opening. Terry at PT said it is rather unusual for that unit to fail suddenly, but that is what it was.

Thanks to everyone for the suggestions and tips.

During the process I did learn a diagnostic trick from Terry. In a similar situation, you can swap out the pressure release cartridges even though they have slightly different settings. One governs the PTO and the other the steering. So, if you've got steering and you swap out the pressure release cartridges and you still have steering, the pressure release cartridges are probably okay.