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Komatsu PC 300-8 Govenor control problem

daterplant

Well-Known Member
Joined
Mar 7, 2010
Messages
52
Location
australia
Occupation
earthmoving repair business owner
I've got a problem with a Komatsu PC300-7 governor control, in engine rpm auto, the engine rpm works fine with any operation of the hydraulics (bucket, boom,stick and swing) returns to low idle when not used, however when you use travel forward or reverse either track/s, the engine rpm drops low idle then hi idle like hunting all the time while the governor control knob is set 100% turn the control to about 90% or below and it works fine, turn the control knob back to 100% hunting starts again, you can see the throttle control linkage engine side, going from full rpm to idle then back to full rpm only when travel is activated and throttle set at 100%.
Anyone come across this before?
 

707

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Joined
Mar 20, 2011
Messages
85
Location
Vancouver, B.C.
Occupation
Heavy Duty Equipment Technician
Im not a 100% sure on the PC300-7 but i know the 200-7 have a strut type of cylinder in between the linkages. Usually ends up failing and causing a hunting issue at the high end of engine rpm. You can easily spot this by simply grabing the cylinder and checking for any lash. Change out that strut and it should fix your problem. Be prepared for the price however...its in the $350 neighborhood.
 

John C.

Senior Member
Joined
Jun 11, 2007
Messages
12,865
Location
Northwest
Occupation
Machinery & Equipment Appraiser
As I recall in the earlier models Komatsu would give you more engine speed and an higher relief valve setting on the hydraulics when you use travel. I don't know if your machine has manual linkages working the speed control on the fuel pump but I used to run into the issue of the throttle lever hitting the high idle stop screw before the computer figured out it was at high idle. The consequence was the extra amperage draw by the motor pushing forward triggered a safety function in the computer to quit pushing and pull back. Once that was cleared it tried again giving you the hunting issue. I used to open the hood and watch the linkage while someone operated the machine to confirm the problem. If you do this, be safe and hang on tight to something. Falling off a moving machine is not something you want to do, ever.

The problem was usually worn linkages that someone figured they would just adjust a bit not knowing that the adjustments were critical to maximum performance.
 

Steve 650

Well-Known Member
Joined
Mar 23, 2013
Messages
83
Location
Canada
a special function for traveling (computer controlled) is making 100-200 higher rpm. When you hit the travel pedal and the rpm is already set a max high rpm, it will try to give 100-200 more and will make the linkage to hit the stop screw. You don`t wanna hit that screw. Ensure the max rpm is set and adjust when doing travel operation. You don`t have to make the entire machine to move, just be gently with a travel pedal to make the pump to stroke, and will make the 'higher travel rpm function' to work.
 

daterplant

Well-Known Member
Joined
Mar 7, 2010
Messages
52
Location
australia
Occupation
earthmoving repair business owner
Thanks guys
You all hit the nail on the head, it was the linkage causing the problem.

Looking at the linkage it didn't look to bad, but there was some wear in it, now knowing that the rpm. is slightly higher in travel helped a lot.
Adjusted the linkage 3/4 of a turn shorter so it stops short of the screw sorted out the problem.
We have ordered a new spring strut and ball joints for either end, and yep about $350.

Thanks again.
 

DK88

Senior Member
Joined
Jan 19, 2011
Messages
320
Location
Ontario
Occupation
Field service tech.
Usually one can just adjust it then, turn the little chamber spring thing so where the bottom was will now be at the top cause they wear a groove in it and by turning it 180 u can get a little more life out of it...
 
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