L3901 won't start

[Shooterrich]

Hello All,

I've owned my Kubota L3901 for about 2 years. It has 103hrs.

My wife drove it out of the pole barn, moved some plants in the bucket to another location on the property, shut down the tractor, and then couldn't get it started.
I walked out to it. I jiggled the F/R pedal back and forth. It started right back up. I pulled it in the pole barn. Before fully parking, I leaned forward to see how close the bucket was to what was in front of me and the tractor shut down due to the seat switch. I couldn't get it to start back up.
I turn the key, the dash lights turn on, but it doesn't attempt to turn over.

I think I've visually inspected all of the safety switches (seat, PTO, F/R pedal switch). I checked the fuses. The battery is not dead. The starter is good.
Should the seat switch click when pushing it up and down?

Yesterday while inspecting it and trying to start it I noticed that there is a PO336 code coming on. I researched that a bit and it seems that code may come on if the tractor shuts down abruptly. I'm not sure, though.

I haven't checked anything with a meter. My father-in-law will come over with one later and help me.

The owner manual isn't much help. I ordered a WSM off of Ebay. I should have it Friday.

I did have a problem with the tractor shutting down last year a few times. I "think" it had to do with rough terrain or some such. I can't remember. In that case I just let it sit for a while and wiggled the seat switch and it started.

Any help would be appreciated!

Thanks!

 

[D2Cat]

You probably just need to adjust the seat switch a tad!

 

[Dave_eng]

This is what I see in the L series DTC codes for P0336.

I do not have any knowledge and am just giving you what I see.

Dave

 

[rk1475]

Had the same problem with my L3800. Turned out to be the HST pedal needed the adjustment backed off. Try putting in neutral, and giggling the HST pedal while turning the starter. That's all it took when the Kubota guy came over.

 

[North Idaho Wolfman]

Go to Kubotabooks.com and get the WSM right now for free if you want to.

Sound like you might have a engine position sensor or wiring issue, but then again I think they throw that code on a Malstart too, so your issue could be from something else like PTO seat HST pedal, switch, maladjustment or failure.

You said you looked at the PTO lever but did you engage and disengage it?
Could very well be the issue.

 

[Shooterrich]

You said you looked at the PTO lever but did you engage and disengage it?
Could very well be the issue.

Yes, I worked the lever a few times. I jiggled it, tried just holding it back, etc.

 

[Shooterrich]

You probably just need to adjust the seat switch a tad!

Is there an actual adjustment that can be made or do you mean whack it with a hammer?

 

[Jim L.]

lugbolt is the member who has a handle on this problem.

I believe that it has to do with the RPM dropping below a set threshold with the key still ON.

The code is stored in the ECU, and can be reset by a dealer.

You might also check to see if your machine has the computer program upgrade to minimize this issue.

While you can check the PTO switch, seat switch, HST switch; on your model they go through the ECU. I would not mess with the seat switch unless electrically disconnecting it to ohm the actual switch itself.

Since the code is showing, I would tackle that first as it will prevent the machine from starting.

 

[thedevilyoulove]

Go to Kubotabooks.com and get the WSM right now for free if you want to.

Holy smokes I paid over $100 for my WSM hardcopy and now I just downloaded the exact same thing in .pdf for free

Thank you so much, kind sir!!!

 

[Shooterrich]

Since the code is showing, I would tackle that first as it will prevent the machine from starting.

So the code appearing could prevent the tractor from starting?

 

[Jim L.]

So the code appearing could prevent the tractor from starting?

Yes, that's what other L3901 operators have reported.

Also, having the crankshaft code displayed causes other things to happen such as lower power output. I would call my service guy and see if they can come out with their magic box and reset the ECU. Also find out what version of software should be up to date for my serial number.

 

[Shooterrich]

I spoke with my dealer today. He emailed me the process to clear fault codes.
He told me that the code was probably due to an abrupt engine stoppage (I think we knew that).
He also told me the code wouldn't prevent the engine from starting but to clear it anyway and call him if the code appears frequently after I get the tractor running.
He said the reason it won't start is probably due to the f/r pedal switch.

I reset the codes and still can't get it started. I guess I'll keep looking into the switches.

 

[Jim L.]

For troubleshooting only, I would take the three switches which go into the main ECU and make them look as normal. The switches are: PTO, seat, and HST pedal.

In the WSM electrical section, it describes each of these switches and whether they are normally open or closed. On the harness connector to a switch, I would temporarily provide the closed or open condition, setting that up with the power off.

Checkout of the switch itself is done by disconnecting the switch from the wiring harness connector and testing it isolated. This is to prevent damaging the main ECU.

Looking forward to what you find.

 

[baronetm]

I had a similar issue with my L3901 tractor quitting and not re-starting. The tractor would not crank and all dash indicators worked as they should and there were no codes.

As a diagnostic tool my dealer had me crank the engine while wobbling the HST treadle pedal it always restarted.

The final repair is in the following thread in my case. Since the repair I have experienced no issues.

http://www.orangetractortalks.com/forums/showthread.php?t=39550&highlight=quit

good Luck

 

[Shooterrich]

I got it started. It was the HST pedal switch.
The lever is not pushing the button in far enough.
I started it by placing a piece of pvc between the lever and button to push the button in further.
I think I need to thread the switch housing in farther. I don’t think you can adjust the lever.

 

[baronetm]

Before adding shim check the placement of the HST switch lock nut. If the lock nut is located on top of the bracket it is assembled incorrectly from the factory, From your photo that appears to be the case. The lock nut should be on the bottom of the switch bracket allowing the switch to sit closer to the switch actuator.

See the Kubota parts drawing for L3901H, Electrical, B10600 Switch/Sensor Rear. See the placement of the jam nut in assembly 060.

 

[whitetiger]

You are correct, the only adjustment is to loosen the jam nut and screw in the switch a turn or so and retighten the lock nut.

 

[lugbolt]

Yes adjust the HST neutral switch.

Don't adjust the seat switch.

P0336 won't cause no-start condition. It'll run with it unplugged. The system will ignore the crank sensor and then use the cam sensor, although, the engine will run a little "off" (sounds weird if you really listen to it), and sometimes with a failed or unplugged crank sensor, they'll fail to.....or improperly regenerate.

There was an firmware update for the P0336 code, but it's an old bulletin from, I think 2013 or 14 and it only applied to certain serial numbered tractors. It'd be worth a call to a dealer and ask them if yours is eligible.

IF/when the engine is "lugged" below 600 RPM (with the "old" firmware), it would sorta confuse the ECU and set a P0336 code. The "new" firmware decreases that threshold to, IIRC 200 RPM and adds a time delay to it, so if it's below the threshold for X amount of time, that's the only way it'll throw a code. There's more to it (a LOT more) but for this discussion's sake, that's all we need to know. Basically you have to kill the tractor "just right" to generate that code with the updated ECU program. That or unplug/damage the sensor itself.

 

[Shooterrich]

If the lock nut is located on top of the bracket it is assembled incorrectly from the factory, From your photo that appears to be the case. The lock nut should be on the bottom of the switch bracket allowing the switch to sit closer to the switch actuator.

You are correct. The jam nut was installed incorrectly by the manufacture.
I loosened the switch. I took off the jam nut. I rethreaded the switch into the bracket and threaded the jam nut on the opposite side of the bracket.
It's odd that it took 100hrs of use for this to be an issue... you'd think I would have had starting issues all along??

 

[Shooterrich]

Thank you for all the help and replies!