Strange RPM Loss?

[Racer71]

I have 80 hours on my L3400HST. When driving from here to there the RPM will just drop. I'm talking a drop from 2,300 to 1,000 in one or two seconds. When I lift off of the HST pedal the RPM will come back up and I can continue on.

This has happened several times. It is just when I am driving and not working the tractor hard. It seams to happen when I am going up a slight grade. The engine can be hot or cold. It is full of fuel. I don't see any water in the fuel filter.

Where should I start looking?

 

[dillo99]

I notice the same thing when driving in heavy snow in high gear (also up a small hill) - I assume it is just that the engine can't handle the load and the drop in rpm's is basically the machine headed toward a stall. If I ease up on the pedal the rpm's rise.

 

[Racer71]

I am using the middle range and I have driven over this area several times without an issue.

 

[john_bud]

Just thinking out loud here...

You have 80 hours, so I am assuming you already know that when the engine starts to bog down, you lift off the hst peddle to allow the engine to recover, so I won't go there.

You've gone over the same area before, and I am assuming again that the ground is in about the same condition. Not a big sucking mud pit now.

Have you done your 50 hour service, changed the filters and cleaned the return screen? There may be a blockage. (Doubtful, but maybe)

I wonder if the governor is operating freely? Take a look around and see if there is any thing that may be keeping the gov from working. Do you hear the engine labor and see black smoke out the exhaust? That would be expected if the governor was giving full fuel and it wasn't enough to keep up the pace.

Best advice is to have a chat with the dealer as it's still under warranty and they should fix it up quick.

jb

 

[PSDStu]

Ditto what JB said about looking at the fuel system, fuel filter etc...

I had a RPM loss problem over the summer while doing some major bush hogging work and discovered that the dual element air filter was filthy and the radiator screens were plugged pretty good.

After replacing the air filter, fuel filter, and cleaning radiator screens real good the normal power returned.

Might not be your problem....but these are some simple things to look at first.

Stu

 

[Soundguy]

I also agree.. I'd look to see if there is black smoke when the engine rpm drops.

Does it sound like a lug down ( should make smoke ).. or a fuel starvation issue ( no smoke.. )..


Soundguy

 

[Racer71]

Right now I am thinking a fuel starvation or bad fuel. I am not seeing the black smoke and I am over loading the engine. This has happened over several (5?) jugs of fuel.

The engine recovers in 1/2 to 1 second after I lift off of the HST pedal and I can go on my merry way.

Does this have a mechanical govenor or is it all electrical?

 

[john_bud]

I am not sure but I thought it was mechanical. But, don't take my word on it !

jb

 

[Soundguy]

Can't answer on the governor either.. but most tractor engine governors are mechanical.. but who knows these days.... I work on old stuff mostly!

If it is lugging down and not able to keep rpms up and not making smoke.. that really makes me thing fuel starvation... as the gov is not keeping the rpms up.. or trying to by revving the engine up and making smoke. Also doesn't seem to be a breathing problem, as that should make rich smoke as well.



soundguy

 

[john_bud]

I checked the manual for the L "10" series and they have mechanical governors. BUT, they don't list any adjustments. Just make sure it is free and the spring is attached.

The mechanism is inside the engine....

jb