M4900 Slow Throttle Response/Low Power

[Tx Jim]

Rob L
Actually I intended to state to remove return line at inj pump. I wonder if lift pump(PN 17121-52030) on inj pump has failed?

 

[Rob. L]

I found the issue, finally! I was taking apart the covers to look at the linkage and I found these 2 "adjustments". I don't know what they are- but they definitely have an impact on the RPM. Someone had taken that cover off and tightened them down tight- which limited the RPM. Crazy, after all of the stuff I did to this tractor, it was something so simple! Anyway, I have attached a pic of what I am taking about. Could someone who knows, tell me what they are and how I need to adjust them? By the way, I am getting about 2800 RPM now and the throttle is much more responsive!

Thank you all for taking the time to help me!

-Robert

 

[kuboman]

That looks to me to be the max fuel adjustment. Don't know why anyone would turn it down to limit power. That adjustment is meant to be specific to that engine. Which is why it has the tamper proof cap on it. Getting the proper adjustment really requires it to be on a test bench but you can do it carefully. Just don't over fuel it. Basically turn it out till you see some black smoke when its working hard.

 

[Rob. L]

Thanks for the reply. So, its the one with the cap I need to adjust? The bolt next to it does nothing? After it was running better, I shut it off because I didn't really know how to properly adjust it I didn't want to mess anything up. Also, when you say "working hard", are you talking about full RPM or the tractor working under a load (with an attachment)?

-Robert

 

[kuboman]

Maybe I misunderstood you. Which bolt do you adjust? I thought you meant the one under the tin tamper proof cap.

 

[Rob. L]

No sir, you understood correctly. When I was loosening the bolt (next to the tamper cap) for a cover, it started spinning the tamper proof cap- that is when the tractor started running much better. I didn't know if the bolt adjusted something as well- or if it was just there to hold the cover on. Also, after you make the adjustment on the bolt with the tamper proof cap, how do you hold it in place?

-Rob

 

[kuboman]

Let me understand you. Did you adjust the bolt under the cap? Or just loosen bolt beside it? The tin cap will turn free. It is not solid to the bolt. It has to be pried off. Once it's off you will see the actual adjusting bolt. If all you did was loosen the bolt beside it and it started running better then something else is going on.

 

[North Idaho Wolfman]

There is 2 fuel injection pump control adjustments:
On the front of the motor is the governor adjustment, set it to max rpm, or under, setting it too high will destroy the engine!
The other adjustment is on the rear of the injection pump mounting area of the block, that adjusts fuel, if it's not blowing black all the time or bogging down when worked (it might blow some black when worked, that is normal), don't adjust it.

the cover over the adjustment bolt is just crimped on.
The bolt on the side holds the stop solenoid bracket and maybe all the way to holding the front cover too.
It's just a rubbing the cover because someone has changed it with the wrong bolt.
On the adjustment there should be a lock nut to keep the bolt from vibrating in or out randomly.

 

[kuboman]

I am betting the bolt was replaced with one that was too long and contacted the fuel rack.
I doubt the fuel adjustment has been tampered with.

 

[Rob. L]

When I loosened the bolt it caused the tin cap, as well as the bolt underneath the tin cap to start spinning. The tin cap does not spin free on this tractor- it spins the bolt inside of it also. And I believe you also answered my question. The only bolt that adjusts the fuel is the one with the tin cap- not the bolt beside it.

Please excuse my ignorance on these matters. Like I said before, I don't have a tremendous amount of experience with diesel engines. I have learned a lot from this one though!

Robert

 

[Tooljunkie]

Wait! Loosening stop solenoid allows engine to rev up? Incorrect or bad solenoid,or as mentioned bolt too long snd interfering with something inside.
Getting close to solving this mystery.....

 

[Rob. L]

I am getting closer to solving this! Thanks to all helping me out! I don't know- might be a combination of that bolt being too long and that fuel adjustment with the tamper cap. I just went out to confirm the bolt inside the cap spins too. I have a newer kubota out here I can compare the amount of smoke it produces when the throttle is increased.