Kubota L3700 won't start

[stoyan79]

The tractor has only 33 hours, bough new in 2011.

I was cutting grass with my 72" cutter and noticed when grass is dense the RPMs would drop, the tractor has lost power and was sputtering. In few minutes, didn't have power to spin the cutter again, so I drove it back to the garage.

I figured it was fuel issue, so I changed the filter and bled the system. Tractor will only start with bleeder screw open, if I close it, it dies.

So I figure plugged hose. Got all fuel out and cleaned hoses with air. Drove to gas station, got new fuel and filled the empty gas tank with new fuel.

Now tractor won't start even with bleeder screw open, although it sounds like its trying to start with bleeder screw open. When screw is closed it doesn't even try.

Figured bad gas cap. Tried to start with gas cap off. Didn't work.

Figured plugged air filter. Tried to start with filter off. Didn't work.

I am out of ideas. Please help.

 

[stoyan79]

After doing some research on the net, next things to inspect would be:

1. Safety switches.
2. Fuel shut off solenoid.
3. Wiring in dash.

 

[art]

If the engine cranks then it isn't the safety switches. Fuel shut off could be the problem but unlikely as it was still working when you drove it back from the work. Might have to bleed at the injectors to get it to come to life. With the bleeder screws open it should NOT help your problem.

 

[LD1]

I still think it is fuel issues with the bleeder or contamination, since that is where the issue started, it is unlikely to be a safety or wiring.

Just went through a similar situation. The tractor wont run with the bleeder open. And it wont bleed with it closed. What I ended up doing to get mine right again was only open the bleeder about 1/4 turn and it would start and run pretty rough and slow like it was going to die. I would then close the bleeder and it would rev up again for a moment and start to loose power again like it was going to die. Then I would open the bleeder a little again, and then close again. Just kept playing with it till it would finally stay running with the bleeder closed.

Not sure how the manual calls to bleed it. I was out in the field when it happened. So sorry I cannot be more help. Bout all I can say is try to get it running again, and then just keep playing with the bleeder. That is if you are SURE you got all the contaminated fuel out of the system.

 

[k0ua]

This is what the manual says.:

 

[stoyan79]

I think you guys are right - it must be air in the system!
The air however has been bi*ch to remove.

I had a bright/stupid idea today, which seemed to bring some progress.

The tractor kept cranking and cranking and it won't start at all, so I created a bit of pressure in the fuel tank, by putting a blow gun connected to my air compressor in the fuel filler hole and not letting much of the air to escape by closing the gaps with my hand.

I did this with the bleeder screw open all the way. I did not put too much pressure, just a bit to push some fuel thru the lines.

Anyhow, every time I did this, the tractor would start, but would run only for few seconds and then die. It won't start again until I created pressure in the fuel tank again.

 

[Chilly807]

I'm going to have a look at the service manual, there may be a "boost" pump before the main injection pump, not just gravity feed. If so, that pump may have gone south.
I changed the filter in mine a few weeks ago, it was a pig to get the air out. I was close to bleeding the air at the injectors when it finally cleared up. They're not easy to get at is all that stopped me from going that route. The engine uses so little fuel at idle, air can take a long time to be pushed out.
You may have an issue with the stop solenoid not releasing the fuel rack completely for the first problem (lack of power), however the fail to start is most likely air.

 

[LD1]

I am still betting air too. Just keep at it.

I have had my filter out a few times now for cleaning. Never ever had an issue. Never even had to crack the bleeder before, just make sure the filter bowl gets completely full, (and even overflow a tad) prior to tightening all the way and locking in the air.

BUT....the last time, got air trapped. And it was a bear as Chilly states. Was on a job to and though I was going to have to pull off. Started loosing power as you mention. Though I was just hitting really dense patches of grass. Pulled the filter and cleaned it thinking I may have gotten some moisture or something. Made another round and it got worse. To the point I could hardly move the tractor as it had no power. Pulled the filter again and had a bear of a time getting it started again. Took about 15 minutes of playing with that bleeder and the throttle pedal. In the end, I think my lack of power was because the bleeder was just a tad loose. Cause I could easily replicate the symptoms of low power and slow reving by just cracking that bleeder. Make sure you get it seated good when you finally get her running again.

 

[k0ua]

In this procedure, the tank is FULL of fuel right? as in above the fuel return line? I am thinking this is important.

 

[stoyan79]

I didn't think of that.

In this procedure, the tank is FULL of fuel right? as in above the fuel return line? I am thinking this is important.