Kubota D1105 Engine - Slow RPM Response to Throttle

[loggin]

Best way to flush is fill and drain a couple of times with hydraulic fluid. Might be a little pricey but is still the best way. As TractorTech mentioned if you can drain the cylinders this will help and may only require a one fill and drain.

Hope this helps!!

 

[dlundblad]

I’ve always considered the D1105 to be a tad slower throttle wise. It’s one of the first things I noticed on my zero turn. Have you heard this machine in good working condition? (Can’t tell what it is.)

It’ll be interesting to see if the fluid and filter change helped. I would think the system’s hydraulic bypass should have prevented any lugging though. Much like picking up too heavy of a load with a FEL and it not moving despite an open loader valve, it should have just bypassed.

 

[Godhungry777]

Hydraulic oil and both suction and return filters have been replaced. No change.

 

[Bavarian]

That sounds gutless.
To me it seems it has some ticking in the engine. Did you check the valves? Next step after that is a compression test.

 

[Godhungry777]

UPDATE

My apologies to all for the delay. It has taken me forever to get hold of a Diesel Compression Tester with the adapters i needed.

So to update:
INJECTOR PUMP > I got the Injector Pump professionally rebuilt and calibrated by our local Bosch injector/pump specialist - no change to over revving, lack of power and bogging under load.

COMPRESSION TEST >
The manual says compression should be 412-469 PSI (Rebuild under 327 PSI)
My results:
Cylinder 1 - 380PSI
Cylinder 2 - 410PSI
Cylinder 3 - 320PSI

So all are below operating range and one below rebuild indicator.

Is low compression also going to cause the slow RPM response to throttle movement?
Or are there still other issues (eg governor) that I'm dealing with for that?

 

[Jerry/MT]

The whole fuel system has been gone through.
Here's what I've done so far:

• emptied and cleaned fuel tank (had water, rust and gunk)
• replaced fuel filters (clogged with water and gunk from tank)
• replaced fuel lines (lines were brittle) - had injector pump and injectors tested - tested ok
• bled injector lines
• replaced engine oil and oil filter
• replaced thermostat and coolant (thermostat was stuck open)
• air filter had already been replaced - exhaust is clear
• checked governor spring, forks and flyweight. Warn but nothing broken or missing

• checked governor spring, forks and flyweight. Warn (sic)but nothing broken or missing

Worn parts? If there is slack in the parts in the pump, you might expect a slow response to throttle movement. Once you set the throttle and the engine accelerates to final rpm, does it hold speed accurately? If the speed wanders with no load I'd expect the governor part of the control is weak.

I looked at the video and it seems to respond to the throttle movement with no load satisfactorily. What am I missing?

However it is not responding to load increase properly. It should droop maybe 100 rpm not 1000 rpm. You are down on compression on two cylinders so that can partly explain the drop but something is amiss. Either the max fuel flow is inadequate or the load is beyond the engine power in this condition. I didn't see any black smoke on acceleration or on load application so I suspect the max fuel flow is not correct. But your engine is worn also. Sorry I can't pinpoint it to a single problem. I would ask the pump rebuilder to comment on the max fuel setting and make sure that is correct as well as the wear in the governor.

If it's not in the fuel control, then you'll need to get the engine compression within spec for all cylinders.

 

[Godhungry777]

FINAL UPDATE - PROBLEM SOLVED
Ok. So after replacing the entire fuel system, the problem was where we first started - the governor flyweight sticking.
NB. For future reference, see my earlier video of the engine running with the throttle plate off so the governor fingers are visible. My original questions in pursuing the governor were to see if anyone knew if the movement of the governor fingers should be noticeable (

). I wasn't sure if the governor adjusting the throttle slide would be big enough to see it move if it was just making very minor adjustments to the slide.
I would now suggest that if you don't see the fingers move under changing load conditions, you should head to the governor flyweight first.
I have no regrets in replacing and repairing the entire fuel system along the way. Everything that was repaired or replaced was in terrible condition and I couldn't believe it was running at all in the condition they were in.
Thank you to all for your input along the way. It's been a great education.
Let me know if you have any questions about the process.