Stalling Mystery

[AndyM]

I am having a issue with stalling.

I start and run the tractor for an hour or so and all is good. Then it suddenly chokes up like its not getting fuel and stops. I have been able to restart it (so far) but once it starts to happen it's go home time.

Other Factors:
Working on a road that is fairly steep. When the tractor is freshly started work progresses fine for an hour or so then trouble starts.
Completed the 400 hour service @10 hours ago. New fuel filters, oil and filter, hst and filter. Cleaned air filter (changed at 200 hrs looks good). Changed rad fluid. Also shimmed up the hydraulics at that time to 2000 psi.
I keep the tank full and both filter and treat the diesel going in.
Algicide is on the way.
Engine temp is always 2 bars - never seen it higher.

What I have done;
Siphoned Most of the fuel out and replaced with new. Run for around an hour on two occasions (at which point it started acting up) and refilled with fresh fuel both times.
Checked seat switch - Ohms are fine (plus it usually quits when I am going UP not down)

I am no mechanic but if it was a fuel issue wouldn't it do it all the time? It's almost like something is shutting down when it gets hot.

Advice please.

 

[Roadworthy]

You can try disconnecting the fuel line from the tank and letting the fuel flow into a container. If the fuel continues to flow freely that's not the problem. If it stops or slows way down you have some blockage in the tank itself. I have an old pickup truck with fuel stoppage issues. Fuel seeps past the block over time and fills the line. Then the truck is fine for a couple miles before starving. So if the filter is good make sure it's getting fuel to the filter. Oh, and don't forget to bleed the air out when you're done. Diesels are real picky about that.

 

[BruceP]

Is there an electric 'lift pump' which moves fuel from the tank to the engine?

When my lift-pump started to fail... the engine would 'stutter' and sometimes stall out.

This is the type of lift-pump I installed on my tractor..... never had a problem since then

http://mooregoodink.com/wp-content/uploads/2017/05/17303.jpg

 

[RCW]

Start with simple things.

First, do you have a workshop manual (WSM)? If not get one at kubotabooks.com

So it stumbles before it quits, it’s not like turning the key off?

Do the flow test Roadworthy mentions, and let the fuel run a bit. Sometimes crap gets drawn to the tank outlet after a while causing starvation.

When it begins to stall, open the fuel tank lid; maybe it’s not venting and causing a vacuum.

If you had to guess, how full is the tank when this happens....full, near empty or varies? Are you always heading uphill when it happens? (This could be related to lift pump Bruce mentions.)

BX’s are also somewhat notorious for the metal tank outlet getting rusted up and causing a similar problem.

Just need to take one step at a time before throwing parts at it.

 

[AndyM]

Roadworthy
Can do on the flow but if it runs pretty regularly for an hour prior you have to wonder why it would suddenly (and fairly predictably) start stuttering, given its not that old (for rusting type issues). But the flow test is on my list.

Bruce P
No Idea but I will see what I can find out - If it does I wonder if its failing when it warms up? if that makes any sense at all.

RCW
Yes, I have a WSM download - little tough to make out the pictures but I do have it.
Yes, it stumbles before quiting and often recovers.
Comments on Flow test as above.
Tanks is Always topped right up (being on the coast I have been pretty religious about that.) Problem seems to start after I have used about a liter/quart or so. And always starts when the nose is uphill.

Thanks all - let me see what I can find out.

 

[D2Cat]

Loosen the fuel cap to make sure the vent is not plugged.

 

[Dave_eng]

Your one comment catches my attention: After and hour of use and nose uphill.

Often the tractor's design allows fuel to flow from the tank to the injection pump by gravity alone.

A pump is added to deal with lower than full tank levels and in addition to situations where the tank is lower than the engine such as going up hill.

The reason the pump is called a "LIFT" pump is because it lifts the fuel up to replicate gravity.

Check the fuse feeding the fuel pump. Check for power at the fuel pump when the key is ON. Check for steady fuel discharge from the pump or filter by opening the line.

Replace pump if fuel delivery is suspect.

When the tractor starts acting up turn around and back up the hill. You will find it runs better if the cause is as i suspect.

Dave

 

[AndyM]

D2
Will do

Dave_eng
You got my attention with that idea - seems to fit the facts. When it starts to act up the first thing I do is try to back down and get to the road on the flat (in case I can't get it started I want to get it to a point a truck can get at it). Usually it still sputters for a bit but then seems to straighten out.
Will follow up as you suggest.

Thanks

 

[Dave_eng]

D2
Will do

Dave_eng
You got my attention with that idea - seems to fit the facts. When it starts to act up the first thing I do is try to back down and get to the road on the flat (in case I can't get it started I want to get it to a point a truck can get at it). Usually it still sputters for a bit but then seems to straighten out.
Will follow up as you suggest.

Thanks

If you achieve success with whatever fix, please report back as it helps everyone.

Dave

 

[Russell King]

If it has an electric fuel shutoff you may want to see if you can disconnect the fuse or solenoid to see if that s somehow shutting off the fuel supply. Just make sure you know that you can shut your tractor down somehow without the automatic shutoff.

It may have a chaffed wire that gets shorted going uphill and when warm. Seems like a slim chance but may be easy to eliminate any possibility of that problem.

 

[AndyM]

I will spend some time on Wednesday trying some fixes - am out of pocket tomorrow. And for sure as soon as I get it under control all will know.

 

[AndyM]

Ok, to follow up. I pulled off the under armor I bought and noticed the fuel pump wires were wrapped outside the fuel lines - rerouted them in behind just in case Russell Kings idea of a wire chaffing might be a problem. -Went to work (uneventfully) for over an hour. Just about the time I was heading back (nose Downhill) , it sputtered again and ran a little rough but did not stall. Tried the open the fuel tank cap - didn't seem to help or hinder as near as I could tell. Kind of sputtered all the way home.

I still suspect the fuel pump as mentioned by BruceP and Dave_eng and would like to test it by detaching the hose out of the fuel pump, ignition to on to see if it's flowing. Good idea or bad? ( I continue to think if it runs fine for an hour fuel must be getting out of the tank ok, no?)

I priced the pumps on Amazon and thought for the price I would just change it out and be done with it (they are cheap). But, I am still under warrantee so using OEM would seem prudent - priced it at $225 loons!! (Waiting to hear from my dealer so not sure if it's a warranteeable item. ) Messick is $130 in real money. Any comments on why the edelbrock Bruce P mentioned or the Amazon cheapy is a bad idea?

 

[Dave_eng]

Ok, to follow up. I pulled off the under armor I bought and noticed the fuel pump wires were wrapped outside the fuel lines - rerouted them in behind just in case Russell Kings idea of a wire chaffing might be a problem. -Went to work (uneventfully) for over an hour. Just about the time I was heading back (nose Downhill) , it sputtered again and ran a little rough but did not stall. Tried the open the fuel tank cap - didn't seem to help or hinder as near as I could tell. Kind of sputtered all the way home.

I still suspect the fuel pump as mentioned by BruceP and Dave_eng and would like to test it by detaching the hose out of the fuel pump, ignition to on to see if it's flowing. Good idea or bad? ( I continue to think if it runs fine for an hour fuel must be getting out of the tank ok, no?)

I priced the pumps on Amazon and thought for the price I would just change it out and be done with it (they are cheap). But, I am still under warrantee so using OEM would seem prudent - priced it at $225 loons!! (Waiting to hear from my dealer so not sure if it's a warranteeable item. ) Messick is $130 in real money. Any comments on why the edelbrock Bruce P mentioned or the Amazon cheapy is a bad idea?

The pump test you mention is OK. You just want to open the line where it is possible to not end up with diesel fuel spilled everywhere on your machine smelling for days. If you open it at the pump have some spare hose so you can direct the flow (if any) into a container.

Dave

 

[AndyM]

Dave, thanks will do.
Andy

 

[Russell King]

If under warranty this should be covered I would think.

The non OEM cheaper pumps reportedly will fail faster than OEM but could be used to eliminate that possibility and if proven to be the issue just get OEM and put it on the shelf and aftermarket pump will never fail.

 

[AndyM]

Good point - buy one just for the test.

 

[lugbolt]

If under warranty this should be covered I would think.

True.

BUT...there is a catch.

In order for a tech (dealer) to diagnose, he's gonna have to duplicate the problem, and verify that it is indeed a problem or whatever. If it only does this after an hour of running on a hillside, the tech is not at all likely to operate the tractor on a hillside for over an hour. If for instance they find a failed electric pump, Kubota only pays X amount of time to replace that pump. I don't know what the rate is, but for instance if it's 1/2 hour, that's all hes gonna get out of the job...if tech/shop has to run/operate it over an hour to get it to act up then change the pump, they lose their backside on the labor. They know this ahead of time and there are two things that are almost guaranteed. One, they ain't gonna be real motivated to spend an hour out there operating the tractor long enough to get it to act up and two, they're not likely to find a problem in the amount of diagnosis time that they're paid, then the tractor comes back as "cannot find problem", though it's likely there still is something going on.

This is where intermittent issues are VERY tough. I deal with this stuff too often. Unfortunately just like a lot of automotive stuff, intermittent issues are sent back to the owner and they're told "bring it back when it's actually broken". Sometimes the dealer techs can accelerate running conditions and "make it happens" sooner, but not always....

 

[AndyM]

Yes, it doesn't seem too likely they will just offer up a part sight unseen. Going to run my flow test to see what info that gives.

 

[AndyM]

Hopefully this will be the final chapter (but maybe not).

It turns out you were all right. I did my fuel pump flow test and (surprise) there was only a dribble of flow. Dealer tells me yes I have warrantee but no, the fuel pump is not part of the drive train. Ok I guess you have to draw the line somewhere.

Of course that begs the question - maybe the pump is not getting any fuel. So, I undo the line prior to the lower fuel filter and, virtually no flow is getting to the pump. Charge up the compressor and blow back to the tank to see if I can clear any obstructions. Good news is I took the cap off prior; bad news is I wasn't smart enough to put a rag over the fill hole - diesel everywhere.

Good news I now have excellent flow. Decide I will drain the tank to see if whatever was blocking it come out. Note the flow is slowing - take off the cap, and the flow Increases - not venting properly. Take the cap top off and note some very small breather holes that are mostly plugged. Cleaned them; flow not too bad. Not sure if the 5 or 6 fir needles I found in the fuel would be enough to block things and have no idea how they got in there but I have found living around here fir needles are like dust in the desert - they get into EVERYTHING.

Put things back together and did a short test run - no issues but I will do the longer test tomorrow.

I learned a number of things, like listen to the OTT contributors - they know of what they speak. Thanks all.

 

[BruceP]

My Kubota has a filter between tank and lift-pump.....as well as filter just before the injection-pump on the engine.

Perhaps you just 'cleaned out' a filter? (shoving all the gunk back into the tank)