JD X749 Dying after 30-45 minutes

[Mike VS]

I don't know how the Yanmar fuel solenoid works but on my Perkins it has a rubber tip and is spring loaded. If you kill the power the spring forces it closed. If you remove it diesel will pour onto the ground. I thought that it has been replaced. If it can be removed without causing a diesel leak then that would be worth pursuing. In the end the idea is to try and eliminate everything but the injection pump $$$$. If you can see fuel in the sight glass then the problem must be closer to the engine.

Looking at a picture of the solenoid it looks like a simple pin that pushes in to shut off the fuel (or pushes in to turn on the flow). This tells me that what ever the solenoid pushes is inside the injection pump could also be broken. I tried doing a search for the solenoid but I found two that look like it but one had 2 wires while most had 3. If it does just have two then if it has power when it shuts off then it's not a safety interlock. I remember Mike saying he tested it but I don't remember how. I would try to rig up a light to the connector. If the light stays on when it shuts off then it's not an interlock.

With a 3 wire system you need to find out what the 3rd wire does. I would assume if this is the case that two wires would just be the power when the key is on and and ground. The 3rd wire come from the computer. If the key is turned off the relay would cut positive to one of the two wires. If the computer thinks it needs to shut the engine down it would do something with the 3rd wire (put power on it or turn power off). A simple multimeter would be very helpful to identify the wires and what they are doing. My simple test with a light would still work but you would need two, one for each wire.

With a 3 wire system you could buy a cheap aftermarket solenoid (hopefully not expensive) and remove the wire that goes to the computer from the connector. Try starting the engine. With a multimeter you could measure the voltage coming from the computer. If it's 12v then you could simply connect the 3rd wire on the solenoid to the battery and run it to see if it shuts off. If it's 0 volts then the engine should start with the wire disconnected and again you could run it to see if it dies.

I know this all reads like a 4" thick novel but that has been done is early posts. (#17)

"UPDATE> Ok, my test lights are complete and here are the results:
The white solenoid lead is the startup power. It does in fact come on with the starter and then go out. The red lead is the hold, and it also comes on when is running and stays on.
So, I finished cutting the grass this morning and was out of work for "overheat testing" so I started in and sat in my yard watching for the light bulb to go out when the engine died. Sure enough 30 minutes later it died and behold the light stayed lit until turning the ignition switch off. So my take is it's not the shut off solenoid but somewhere else, although if I had not just replaced it I would have suspected it to be bad."

 

[Diggin It]

So my take is it's not the shut off solenoid but somewhere else, although if I had not just replaced it I would have suspected it to be bad.

But what we don't know is if whatever that plunger is supposed to push or pull is working properly. That's what the guy suggesting removing it is going for. Remove it, let it hang (securely somehow, wire ties?) Leave it connected with your test lights. But you'll have to figure out how to start and stop the engine and how to prevent any oil and/or fuel leaks.

But if your under any kind of warranty, I'd let the dealer have a go before doing anything that might void it.

.

 

[Mike VS]

But what we don't know is if whatever that plunger is supposed to push or pull is working properly. That's what the guy suggesting removing it is going for. Remove it, let it hang (securely somehow, wire ties?) Leave it connected with your test lights. But you'll have to figure out how to start and stop the engine and how to prevent any oil and/or fuel leaks.

But if your under any kind of warranty, I'd let the dealer have a go before doing anything that might void it.

.

Warranty? I assure you this post would never have been started if I had one.
As for removing the solenoid, I'm going to try it when I can get out there and make that cover plate. There is no fuel involved only oil.

 

[crazyal]

You might want to remove it and turn the key to the "on" position with it plugged in to see which way it moves. If it pushes into the pump then it's probably not going to work. I think it's looking more and more like the injector pump. Maybe you can remove just the end of the pump where the solenoid is (maybe after mowing season is over). Or possibly talk to someone who rebuilds them to see if there's a solution that doesn't require a full rebuild.

 

[Mike VS]

You might want to remove it and turn the key to the "on" position with it plugged in to see which way it moves. If it pushes into the pump then it's probably not going to work. I think it's looking more and more like the injector pump. Maybe you can remove just the end of the pump where the solenoid is (maybe after mowing season is over). Or possibly talk to someone who rebuilds them to see if there's a solution that doesn't require a full rebuild.

You might be right... I sure hope not.
And the plunger pulls back.

 

[oldnslo]

If you have the old shut off solenoid can you just cut the plunger end off to create a test plug? Would have to figure out how to shut engine off though.

 

[Mike VS]

If you have the old shut off solenoid can you just cut the plunger end off to create a test plug? Would have to figure out how to shut engine off though.

Already ahead of you. I figured I'd hook up a SEPARATE hot wire to engage the plunger. It would not be in the electric circuit of the mower.

 

[dieselscout80]

If you were to drive for the same amount of time, but without the PTO engaged would it still die?

 

[Mike VS]

If you were to drive for the same amount of time, but without the PTO engaged would it still die?

Well, I have not driven around sightseeing, but last month I kept it running at the garage (w/o PTO) and it died at the expected time.

 

[Myz28u]

Again form memory, the shut off solenoid should be a three wire. One ground, one pull in circuit(high current) and one hold in circuit (lower current). Used to be red,black and white. The pull in coil activates with the key switch once the parameters are met and pulls the pin in on the solenoid letting the plunger in the injection pump move back due to spring pressure.
There is a timer circuit that shuts off the relay for the pull in coil after a few seconds. The hold in circuit should be activated and holding in the solenoid via a relay on the third wire. (Low current draw)This will stay held in until the key is cutoff,a safety switch/engine protection switch is opened or the hold in relay opens up for some reason.(like a bad relay getting hot).
Like I said this is from memory on this model from around 2012. So it may have changed.
Hope that helps.