X750 random stall, restarts ok

[KennedyDiesel]

This is a 2013 or so model. Been running great as all Yanmar engines do, but began stalling at cold start. It will crank, and typically fire quickly as normal, idle a few seconds then shut off just like I switched the key off. No labor or sputter, just dies. Crank it again and fires right back up. Sometimes it repeats, sometimes it stays running. Sometimes it takes half dozen tries. I thought it might be the brake switch as cycling the brake pedal seemed to get it to go, but I think that turned out to be random luck of the draw. It is getting progressively worse to where now it will sometimes stall after running for a while.

I had a look at wiring, etc and soo nothing out of the ordinary. I'm kind of leaning towards the shutoff solenoid on the injection pump, but leery that it could be a safety control. I know there is an inhibit switch for the PTO that shuts it down when the coolant temperature gets high, but I have not seen where the switching or logic is located for things like this.

Recap: Start/stall with parking brake engaged. Has progressed to stalling occasionally during operation. I don't know that it has ever stalled with PTO engaged

Hoping someone else has had this issue and can shed some light.

 

[2manyrocks]

This may be a really bad guess, but is it possible that some safety shut off switch has become intermittent causing it to shut off randomly?

 

[KennedyDiesel]

If it was during operation I might suspect these as potential issues. I do have the seat switch jumped as well as the RIO since day 1, but I don't see how they would affect engine operation with the parking brake on. PTO will not come on with brake on either.

 

[2manyrocks]

FWIW, I jumpered my seat switch, too, but over time I think the jumper loosened up and sometimes my mower shut off.

 

[Richard001]

I'm kind of leaning towards the shutoff solenoid on the injection pump

I think your assumption is correct. If you can figure out which wires that go to the solenoid are for the hold coil. put some push pins into to the wire, connect a volte meter to them after the engine stops. Don't do anything else, just measure the volts.

If no voltage across the hold coil, you have found the problem. If you have voltage, then the problem is either the connector or the solenoid.

Richard

 

[KennedyDiesel]

I think your assumption is correct. If you can figure out which wires that go to the solenoid are for the hold coil. put some push pins into to the wire, connect a volte meter to them after the engine stops. Don't do anything else, just measure the volts.

If no voltage across the hold coil, you have found the problem. If you have voltage, then the problem is either the connector or the solenoid.

Richard

That is a great suggestion, but with the immediate restart a guy has to wonder if the power loss will actually show? It seems to be self resetting and almost immediate, like a poor connection. It has only ever shut down when running mid to full throttle a couple of times. I've not heard what I would consider a brief cut out/on either.

The PTO clutch has never disengaged during operation and I don't know that it has ever stalled while mowing.

I do wonder about the key switch as well.

 

[KennedyDiesel]

FWIW, I jumpered my seat switch, too, but over time I think the jumper loosened up and sometimes my mower shut off.

I used a piece of small gauge solid copper wire probably 20 or 22ga from an old fluorescent light fixture. I pushed it through the holes in the terminals of the switch. When the blades push on they fold the copper over and sandwich it tight. Also dielectric grease.

 

[jonsstihl]

I have had the overtemp switch trigger when my x758 had a bunch of dandelion seeds over the intake screens that I hadn't noticed. In my case it just shut off the PTO.

for the immediate restart when you cycle the key you are back on the start cycle of the solenoid instead of the hold.

when the engine is warm, and you start it as soon as you turn the key does it run longer than if you turn the key to preheat and wait for say 5 or 10 seconds before actually starting the engine.

 

[jonsstihl]

i realize this is an old thread and you probably fixed it by now but... any update would be appreciated. mine has been running flawlessly so far but you never know when that might change