L39 TLB still running poor

[medarocket]

I have a 2007 Kubota L39. 820 HRS maintained. This issue started 3 years ago but doesn't interfear with my work 80% of the time. I can use full function of my backhoe and loader and never know there is a problem. I run into a problem when I have useing high RPM's on a road ride or brush hogging. This engine's full RPM's when running good are 2900. When I have the issue it falls to 18-1900 and still burps and smokes. If I were to never exceed 20-2200 RPM's it will run good all day long never know that there was a probem. This also is not an issue on or 15 mins after a cold start. It will run flawlessly any cold start and 15 mins after. A month ago I had it run like a top for an hour brush hogging really heavy grass usually like 2600 RPM's. The last 15 mins should have taken 5 but it started acting up. When It acts up I can back off to an Idle for a moment and it will not hesitate back to full 2900 RPMS for about 20 30 seconds then it will burp and fart again. There is a lil more visable smoke when it occurs but more noticibly is the fumes that i can smell. So because I have a few more brush hogging jobs to do and I cant stand it running bad anymore I pulled it all apart.

1. Drained Fuel tank from line from filer houseing - no inconsistant flow no hesitaion on 7 gals of fuel

2. Removed line from tank to filter houseing and blew thru it both ways.

3. Removed tank clean fuel thru it x 5 and dumped. Very little debis in tank for 5 years of use, A few grits of sand and a small sliver of grass. No water No sludge. Blew tank out wiped inside with a rag new fuel and Dumped one last good luck time.

4. Removed every return line blew thru with compressed air both ways.

5. Removed line to injection pump, same thing both ways.

6. Replaced fuel tank blew line on tank side into filter housing when it was conneceted to get the housing clear.

7. New O-ring on filter houseing new O-ring on fuel bowl. Brand New fuel filter

8. Replaced with new fuel

9. Let air excape fuel bowl and tightened.

10. Blead line to injection pump good fuel flow to there.

11. Replaced inner and outer air filter brand new

12. Starting was tricky and took my dad and I 20 minutes cracking injectors and it felt like too long for fuel to get there.

once I got it running I let it warm up idleing for 5 mins. Then went full throttle 2900 RPMS while I cleaned up tools and such. It screamed unloaded for 20 mins not a sign of an issue. Went down the road for 5 mins no issue back up the road and this is no major grade just barely not level and it came back up 4 mins no issue and just as I was confident it was fixed It started burping again and back to 18-1900 RPMS. Sounds like its starving for fuel looks like its starving for air. When you run it for only 15 minutes on a cold start you would never know theres an issue.

It has nothing to do with the temp guage, temp guages shows operating temperature in 5-8 mins. I believe its when the compartment gets fully up to temperature.

I have tried everything I can think of. I have tried running it without the fuel cap no difference. I have had it act up going down a hill for few hundered yards then turn back up hill and it run great. other times It runs good down hill turn around it and runs terrible. But what is consistant is the 18-1900 RPMS. It never has stalled or ran bad below that. I really thought I was going to find a leaf or something in the tank and I would have never put it back on if i didnt know that there was nothing in it. I could see the whole bottom of the tank with a flashlight thru the sending unit hole.

So because I feel like I wasted my whole day with the same results I started with I am upset and tired and here.

I cant wait to be able to solve this issue, thanks in advance

 

[Breeze]

I read your post and it seems like you have done a lot to try to solve the problem.

The absolute basics:

A diesel engine requires fuel, air and compression and proper timing to bring the three together at the exact right time.

I'd toss compression problems in your situation.

Likewise, it doesn't sound like lack of air, although a disruption of air flow at higher rpm would not allow for proper combustion of fuel.

I don't know how injectors with issues react at higher rpm/load. It seems to me that if they are good at 2200 rpm, they would be good at 2900 rpm?

While you have focused on fuel starvation, your comment about smoke would indicate excess/unburned fuel? Is there any increase in crankcase level caused by fuel going South, through the rings? It seems as if higher rpm/load is causing excess fuel in the cylinders. You could try adding an injector cleaner to the fuel, just for grins. I'd probably also revisit the air intake, just to make sure it is breathing properly.

Perhaps someone with greater fuel pump/injector knowledge will chime in or someone with greater knowledge period will have a different guess.

 

[medarocket]

Today I used the tractor again brush hogging and it was terrible. It seems that when its hot its worse, honestly in the shade in the afternoon it was a lil better I could only get about 1500-1700 out of it and still running poor. Not even enough power to get it to cut good. This job when the tractor is running good not even perfect takes be an hour and today it took 2.5.

Once it gets to the point where its acting up it will have a problem even without load on it. I also popped the hood with it full throttle when it was not acting up and starved it for air with my hand. a storm of smoke rolled out as it should and then recovered perfect immediatly. As i did this it did not duplicate the sound or feeling that occurs when it is acting up.

I also did this when it was acting up. It did not seem to increse the bogging beyond what it did the first time just starved it for air and tried to power thru it while it smoked again.

I really cant see how air is the factor.

One thing i find odd with regard to fuel is when i was brush hogging and I got a bit of ground or a heavy wad of grass and it loaded up the tractor and bogged it down from being over loaded, after the load surge the tractor seemed to run good for a few seconds or nearly perfect.

I would think that when I loaded up the PTO that it would require more fuel... so when that load is released its nice that it comes back to normal but how if there is a restriction of fuel and it is starving for fuel to begin with and you ask for more it somehow is getting it and then gets enough for it to surge almost back to full RPMS.

Is there a way an injector or the injection pump could be intermittantly having trouble.

One thing to add to the Bogging situation is that when at full RPMS, the first sign of trouble is a little miss, then another miss. every second or 2 then more and more while losing RPMs Its no a sudden 100 % missfire and your down to the low point it slowly loses power more more untill it feels as though its running on 2 cylinders.

Hope something here will help figure this out.

Thanks

 

[Kytim]

My bet is a sticky injector. Just a feeling.

 

[kuboman]

Your tractor will have a mechanical lift pump. Either electric or engine driven. I would check it. If it is an electric pump I have had them cause problems. They can be very intermittent and hard to diagnose. The engine driven mechanical will either work or not.
You problem sounds fuel related to me and if you have not trouble shot the lift pump then I would for starters.

 

[medarocket]

Your tractor will have a mechanical lift pump. Either electric or engine driven. I would check it. If it is an electric pump I have had them cause problems. They can be very intermittent and hard to diagnose. The engine driven mechanical will either work or not.
You problem sounds fuel related to me and if you have not trouble shot the lift pump then I would for starters.

This tractor is gravity fed to the filter housing and out to injection pump no lift pump.

This problem has been ongoing for like 3 years. Hasnt really gotten worse or better in the same situations. In the winter its almost non existant. I dont know if that can help detrermine the chance of it being an injector.

 

[kuboman]

This tractor is gravity fed to the filter housing and out to injection pump no lift pump.

Are you sure??? Have not seen a kubota yet that does not have a lift pump. It will be on the side of the injection pump if mechanical, or somewhere inline if electric.

 

[kuboman]

Just checked online and yes it has a mechanical pump on the side of the injection pump.

 

[Kytim]

Ding, Ding, Ding. Looks like we may have a winner!

 

[medarocket]

Just checked online and yes it has a mechanical pump on the side of the injection pump.

Ok that is possible, thought that was all considered the injection pump. But when i take that hose off to it, it flows good to that anyway...i would guess 1/3-1/2 gallon a min free flowing thru filter... doesnt seem like it has to pull it at all and you said that the mechanical ones will either work or not, no itermittant issues.

So wouldnt that eliminate the lift pump as the culprit?

 

[kuboman]

Ok that is possible, thought that was all considered the injection pump. But when i take that hose off to it, it flows good to that anyway...i would guess 1/3-1/2 gallon a min free flowing thru filter... doesnt seem like it has to pull it at all and you said that the mechanical ones will either work or not, no itermittant issues.

So wouldnt that eliminate the lift pump as the culprit?

Most likely, I would pull off the outlet(pressure) hose and make sure it has good pressure when you crank the engine.
Other than that you may have sticky injectors or delivery valves in the IP. Have you tried a good dose of injector cleaner/lubricant? If not I would try that for a few hours.

 

[medarocket]

Most likely, I would pull off the outlet(pressure) hose and make sure it has good pressure when you crank the engine.
Other than that you may have sticky injectors or delivery valves in the IP. Have you tried a good dose of injector cleaner/lubricant? If not I would try that for a few hours.

On the first 2 hrs of brush hogging yesterday I did for the first time try that Diesel 911 that was reccomended. That was in the first 2 gallons of fuel I put in it after the work. I ran that as low as i dared and then thru a fresh 5 gallons in that was again untreated. NO difference in performace with the treatment.

 

[Apogee]

I would second the lift pump.

The other thought that comes to mind is the possibility of either a crack in the fuel supply line or possibly the fuel filter housing leaking air. Bottom line, an air leak someplace before the injection pump.

My gut still says to me lift pump. You noted "12. Starting was tricky and took my dad and I 20 minutes cracking injectors and it felt like too long for fuel to get there." I would start with the lift pump and if that doesn't fix it, then I'd pull the injector pump and take it to a shop to be checked.

I recently ran into an issue with my B9200 where the fuel valve on the filter housing had been bumped about half closed. I have no idea how it happened, but anyway, it acted just as you describe. It would idle and run fine at low rpm, but as soon as I started to do any real work with it, it would start surging and missing. It had been doing it for several weeks and I figured it was a plugged fuel filter and I just hadn't gotten around to changing it. I was in the process of finally checking to figure out the problem when I found the little valve on top of the filter housing turned partially off and waalaa, problem solved.

Good luck!

Steve

 

[Apogee]

You might also check out posts #12 and #36 from this thread:

http://www.tractorbynet.com/forums/parts-repairs/232471-another-kubota-wont-start-fuel.html

Are you bleeding per the instructions in the manual? It sounds like there is a specific procedure that is a bit different, hence why I asked.

It might be well worth grabbing a shop manual for it if you don't already own one. Messick's is a good source for reasonable money. And yeah, Kubota is very proud of their manuals from a $ standpoint.

Steve

 

[medarocket]

I got it to bleed on like 2 gallons maybe that is why it took so long but it did run flawlessly going up the road. I have never seen a diesel run good at all if it was not 100% blead. I never looked up or researched how to bleed it, just did as I have gotten every other diesel to start... i would love for that to be the problem. I know that when i would turn the bleader on the pump that it would nearly die and ran terrible at an idle but when i closed it it would run perfect. So my thought was it was blead.

Am I wrong?

Does anyone have the exact bleeding insturctions for this engine?

 

[Scrounger]

Seems most Kubota's have clear fuel filter housings? Have you looked at that container to see that it is full of fuel when you are in the middle of the problem?

I'm also thinking that temperature is involved as you indicated? Seems weird it never acts up in cold weather? With that said, I'm leaning toward injector pump or injector. Any chance of removing the injectors & cleaning them?

Keep us posted?