3240 rpm problem?

[cjb]

After using my 3240 for 30-45 minutes, the rpms go up and down. It has a hydrostat transmission. Does not do it in cruise. Any suggestions as to what my problem is?

 

[Bulldog]

When you say the rpm's go up and down what are you doing?
Are you going up a hill, flat ground, pulling a disc, plow, bushhog or what?

Not having any other info the first thing that comes to mind is a dirty fuel filter. When was the last time it was serviced?

 

[cjb]

It occurs no matter what I am doing. It only happens after the tractor is used for like an hour or so. It doesn't seem to occur in reverse. But, it does do it in cruise and forward. I didn't think it was doing it in cruise, but I checked that today and it does have the problem in cruise also. The loader and the lift arms operate as they should when this problem is happening. The tractor just goes fast and then slow, then fast, then slow. There is no problem with the fuel. It is really hard to explain this problem. But, any ideas about what is going on will be greatly appreciated!

 

[Bulldog]

Does it sound like the hydraulics are loading up when it does this or is it just something in the engine?

Does it feel like the transmission is slipping?

 

[cjb]

Seems more like hydraulics.

 

[KubotaTech]

Sounds like a fuel issue. Change the filter and make sure when you have the sediment bowl off that when you open the valve you have plenty of fuel flowing out. Also when it is running and starts to act up, look at the bowl and see if there is any diesel fuel in it. If you can see it sucking fuel out and the level is going down, there is a restriction between your filter and the tank.

 

[cjb]

I'll try that and see. Hopefully that is the issue.

 

[OkieDavid]

Sure sounds like a fuel problem. Could be a clogged fuel tank vent and after 30-40 min of operation you are pulling a vaccum on the tank. If the fuel filter doesn't fix it, next time it starts acting up- crack open the fuel cap. That will tell you pretty quick if it's not venting properly.

 

[Stubbyie]

Agree with fuel problem in some context.

May have particles / flakes in fuel tank plugging fuel pick-up.

Compare what happens if tank full or nearly empty.

Slight possibility could be a mat of biofilm due to contaminated fuel.

Other threads here have reported pine needles and oak leaves in tank sucked down against pick-up point.

Only certain way to clean tank if determined to be a problem is to pull it and wash thoroughly and triple rinse, last with a couple quarts of alcohol to remove soaps-detergents-cleaners to prevent fuel gumming on contact.

Please post back with your findings and repair for all to learn.

 

[cjb]

Today I replaced the fuel filter. Plenty of fuel entering fuel filter. The tractor still has the rpm problem. Removed the gas cap. That did not help. There is no 'error' message on the panel. Drove the tractor. The varying rpm problem does not occur in reverse or in cruise. Only happens in forward, does not matter what the speed. Any more suggestions?

 

[cjb]

Also, the hydraulics are working fine. The transmission does not seem to be slipping.

 

[cjb]

Also, the hydraulics and transmission seem to be operating fine.

 

[OkieDavid]

Thanks for the follow up. Now I am leaning toward contaminated fuel in the tank. Not sure if your fuel pickup is at the front or rear of the tank but here is my thinking.

A small amount of water is settling in the bottom of the tank. If the fuel pickup is at the rear of the tank, when moving forward- the water sloshes to the rear of the tank and gets picked up causing performance issues. As rpm drops, the governor calls for more fuel...a smidgen of good fuel gets picked up and then due to the governor opening, the engine races.....In reverse, the water sloshes toward the front of the tank and clean fuel is then picked up and engine runs fine.

One idea would be to park the tractor on an incline/decline depending on the fuel pickup location and "stick test" the tank with a piece of tubing....see if there is any moisture in the tank. If so, drain/clean/replace.

Not a scientific guess but a shade tree head scratching session of "what in the world can be causing this". ETA: I'm also sticking with cheap easy diagnostic testing methods...aka: rednecking it

 

[cjb]

We will try that. It is getting low on fuel, so I may just drain the tank and see what happens when new diesel is put in it. It is worth a try. A fella said maybe it is a forward solenoid on the HST pedal. I hope it's the fuel!!!

 

[cjb]

Drained the fuel tank. Put new diesel in it. The tractor still has the rpm problem, after it warms up. It only does it when the tractor has been used 40 mins. or so. Any more suggestions?

 

[OkieDavid]

Note: still just thinking out loud here but you mentioned the solenoid, don't know if it is possible but could you reverse the solenoids so reverse is forward and see if the problem persists? If it goes away then that would lend some credibility to the solenoid being bad. Obviously caution would be in order but if the solenoids are the same it could be used as a diagnostic tool.

I'm struggling with this one as it contains several variables (many of which you have eliminated so far). It strikes me as one of those that is a very simple fix once identified. When you say the rpms go up and down, what varience are we talking about?

 

[cjb]

For example: if I am trying to hold it at 2.4 mph, if the engine is cold, it stays right there. Once it gets hot and starts acting up, it will be 2.4, then 1.9 mph.

 

[kuboman]

You need to clarify is it the speed of the engine that changes or the speed of the tractor and the engine stays at a constant rpm?

 

[Bulldog]

Not sure if your tractor even has this but thought it was worth a shot to ask. Does it have a vent cock at the pump? If so is it close? If it's left open it can make the engine run bad or even die.

 

[cjb]

The L3240 in question is open cab rops model no AC. Today I again worked it until it got warm enough to act up. I tried it in low- medium and high, same problem. I tryed it with auto throttle and manual. In manual it worked as it should. In auto it has the problem except going in reverse or using cruise all the way forward,then it acts as it should.I noticed today in auto if I held the pedal down all the way, full throttle, it would stay constant at 6.7 mph, if I dropped off say 4.0 it would fluctuate say 3.6 to 4.0 up and down. This is engine speed and rpms. It is hard to explain but when it does this it feels like the wheels are egg shaped if that makes any sense.