Komatsu FG25ST-14:
K-21 starting and running problem

This truck was sent to our shop because another shop had been unable to solve a starting and running problem.
Though communication between the 2 shops is scant at best, the complaint was that the engine was usually difficult to get started requiring a long crank period and when it did finally get running it did not want to accelerate.
Upon arrival at our shop the reported condition would occur about 90% of the times we tried to start the engine.
Using our Hitachi diagnostic reader (SST) I found 3 stored codes:
P2138, P2122, and P0650.
The P065 was simply that the MIL lamp was missing from its position in the monitor panel (perhaps left out intentionally?)
The other 2 codes suggested to me that the APPS (which appeared to be brand new!) might not have been properly adjusted and given the proper "learning" procedure.
Using the SST data display I adjusted the APPS to the correct voltage range, then I ran the idle fuel learning exercise with the SST.
Doing this apparently "solved" the starting and running issues on this truck because since doing this, the engine starts quickly and accelerates readily every time it is cranked.
My concern is that I have no previous experience about what problems failure to adjust a new APPS and administer the learning procedure will cause. Our shop has never replaced an APPS without adjusting and "teaching" it so we don't know for sure if we have actually addressed the root cause or not.
All I know about the "original problem" that caused the other shop to replace the APPS with a new one is that the truck suddenly would only idle and would not accelerate.
Just wondering if there are any Komatsu or Nissan K-21 techs reading this forum that might have experience to whether the APPS settings could have been the problem ever since the other shop replaced it.
  • Posted 25 Apr 2012 02:11
  • Discussion started by L1ftmech
  • Tennessee, United States
Showing items 1 - 10 of 10 results.
I ran across several trucks that starts, runs fine but won't do anything other than idle or runs fine wide open then 2 minutes later, it will only idle no matter what.

Check the battery and alternator output voltage. Most likely the belt is slipping on the alternator pulley. Probably only has 11.5-12 volts output.

Tighten the Alternator Belt and recheck. You should have now a constant 14.3-14.4 volts. Problem solved!
  • Posted 7 Feb 2016 11:41
  • Reply by lance_d
  • Indiana, United States
We have a FG25ST-14 that won't accelerate. I did the manual learn and it seemed to be cured. After running lift a couple of minutes it started doing it again. No parts have been replaced.
  • Posted 13 Mar 2013 23:27
  • Reply by FORKLIFTDOC
  • South Carolina, United States
Anytime you move or adjust an accelerator pot, you must perform a manual relearn by key on 5 seconds then key off 10 seconds, key on 5 seconds key off 10 seconds (2 times), this will relearn the throttle and accelerator positions to the ECM. If it is not done you can have no acceleration and hard start.
  • Posted 30 Aug 2012 23:36
  • Reply by Steveray
  • Georgia, United States
Jplayer, thanks! And no joking, I do wish I could send them a bill, but the satisfaction of solving a problem they created themselves..........and then dead lined the truck for 5 MONTHS while they scratched various body parts..........stumped so badly they finally gave up and sent the truck to us...............as has been said elsewhere, absolutely priceless.

Now on this other issue of learning the ropes of this forum.
I have visited the forum for a few years periodically and finally decided to join up. I'm just gonna have to do my home work on the navigation techniques used here.
  • Posted 26 Apr 2012 00:49
  • Reply by L1ftmech
  • Tennessee, United States
L1ftmech,
of course i said that in jest about the bill... well i sorta did but all is well, no bill? okiedokie ;o)

click on MEngr's name in the header of his post and it will bring up his information on him with email address sir ;o)
  • Posted 25 Apr 2012 20:48
  • Modified 25 Apr 2012 20:48 by poster
  • Reply by Jplayer
  • North Carolina, United States
John Player Jr
_________________
LiftOne, LLC
Charlotte, NC
Email: jplayer@liftone.net
Jplayer, of course I wish there was a bill to send them but as both our shops are just 2 of many in a national fleet network, there is no billing to be done.
MEngr, to me url means Uniform Resource Locator, commonly known as "website address".
Signature without CIE?
What the heck is CIE?
  • Posted 25 Apr 2012 14:58
  • Reply by L1ftmech
  • Tennessee, United States
Liftmech;
url is Signature without CIE=
  • Posted 25 Apr 2012 10:59
  • Reply by MEngr
  • Missouri, United States
L1ftmech,
no cryptic answers here buddy
to answer your question about any further damage that may occur from a mal adjusted pps?
other than it not wanting to run correctly? none that i know of.
The pps and the tbs were not aligned so it didnt know what to do... plain and simple :o)

installing a pps is a fairly simple thing if done by a professional with the right tools. I've seen too many techs try to play it by ear or eyeball it and thats just not possible and get it "right".
I'll bet you they did this and got it wrong and couldnt figure it out. Being that all you did was relearn the system and it returned to normal pretty much tells the story doesnt it?

Send the truck back, send them the bill and smile and say "have a nice day" ;o)

Job well done.
  • Posted 25 Apr 2012 09:54
  • Reply by Jplayer
  • North Carolina, United States
John Player Jr
_________________
LiftOne, LLC
Charlotte, NC
Email: jplayer@liftone.net
MEngr, does this forum have a provision for private messaging? as I do not see your URL or e-maill address posted in your profile either.
  • Posted 25 Apr 2012 03:18
  • Reply by L1ftmech
  • Tennessee, United States
Liftmech;
You have working in your region the manager of technical service for the company that manufactured the engine you are in question about. If you had your url posted in your forum profile I could tell you how to contact him for an answer.
  • Posted 25 Apr 2012 02:43
  • Reply by MEngr
  • Missouri, United States

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