Generators and Motors
[Home] - [HELP] - [Forums] - [Library] - [Photo Gallery] - [Groups] - [Classified Ads] - [Subscribe] - [Links] - [Books] - [Sponsors] -

Go Back   SmokStak > SmokStak® Vintage Electrical Equipment > Generators & Electric Motors General Discussion > Kohler Generators
Forgot Password? Join Us!

Notices

Kohler Generators Restoring, maintaining and operating vintage Kohler generators.

Kohler Generators

Kohler 12 Res Natural Gas Gen OS fault


this thread has 36 replies and has been viewed 5397 times

Reply
 
Thread Tools Display Modes
  #1  
Old 05-06-2015, 10:30:54 AM
Trekrider2001 Trekrider2001 is offline
Registered-I
 
Join Date: May 2015
Location: Woodinville, Washington
Posts: 60
Thanks: 4
Thanked 2 Times in 2 Posts
Default Kohler 12 Res Natural Gas Gen OS fault

This is my home generator set. It won't run now. It starts, kicks in like its starting and then stops. The display says OS, for Over Speed fault, but that has to be bogus as the unit barely started. Runs for about 1 second. Any ideas? My guess is that it is fuel starved, so I'm looking at the input. I have a dedicated regulator feeding fuel off a 2 lbs meter (the house has its own regulator). I put this in years ago when the gen was hard starting, hence, my current theory of fuel starvation. I measured the voltage at the gen fuel solenoid and see 12 volts. During cranking I see the voltage drop to about 9 volts but I have no min reading voltmeter so this is a close guess. My theory now is that the voltage drops too low for the solenoid and it cuts off the gas right when it needs it the most. The battery is now 8 years old but it tested OK when I took it into the shop, but I think a new battery will fix this. Anybody have a better idea?

Update: changed the battery, no joy... ideas please.
Reply With Quote
Sponsored Links
  #2  
Old 05-06-2015, 10:13:05 PM
Joe Batts Joe Batts is offline
Registered-II
 
Join Date: Jun 2009
Location: NJ
Posts: 57
Thanks: 2
Thanked 7 Times in 7 Posts
Default Re: Kohler 12 Res Natural Gas Gen OS fault

Check your gas pressure feeding into the regulator on the gen. It should be at or damn near close to 7-11" water column (26"=1lb.). Check your vents on the gen monted regulator to see if they're clear. Check to make sure the bolts mounting down the carburetor aren't loose as the gen mounted regulator needs to develop vacuum off the outlet of it to start fuel flow (you can usually just grab the air cleaner and see if it moves). Check your carb linkage to make sure it's free and not binding up (try running the throttle by hand if necessary to be sure the throttle is operating properly). 8 vdc or higher for battery voltage during cranking is usually fine. Check your plugs to make sure the unit isn't running on 1 cylinder (make sure plugs are seated and gapped properly - .030). Start here and let us know.
Reply With Quote
  #3  
Old 05-07-2015, 02:42:11 PM
Trekrider2001 Trekrider2001 is offline
Registered-I
 
Join Date: May 2015
Location: Woodinville, Washington
Posts: 60
Thanks: 4
Thanked 2 Times in 2 Posts
Default Re: Kohler 12 Res Natural Gas Gen OS fault

Ran through the check list above:
1) Gas pressure: I don't have a gauge, but gen has its own feed from the house. The main regulator is a 2 lbs system and the gen has it own regulator. So I adjusted that 2 turns higher and then one turn lower. No change in gen operation. I is now returned to what it was.
2) Vents on gen regulator and the utility one are all clear
3) bolts on carb all tight
4) carb linkage moves be hand and during the starting process
5) I replaced the Battery. With new battery I get ~10 volts at the fuel solenoid
6) I replaced and gapped the plugs to .030
Additional info:
A) when you look down the throat of the carb you see a disk. This is normally closed. during cranking, this opens fully. When it shuts down, this closes again. Is this correct? Your comment says that it should develop a vacuum, but as the gas enters under this disk, opening it fully would give you the least vacuum. What is that disk? In a gasoline carb, I would call it a choke and it should be closed during starting. Do NG carbs work the opposite?
B) I noticed that the oil level was a bit high so I drained out about 4 oz and now it is just at the full mark. But no change in the generator operation.
C) the snubber diode across the fuel solenoid measures 0 ohms in the forward and 5 M-ohms in the reverse when it is removed from the circuit. I take that as a good diode.
Reply With Quote
  #4  
Old 05-07-2015, 11:02:34 PM
Joe Batts Joe Batts is offline
Registered-II
 
Join Date: Jun 2009
Location: NJ
Posts: 57
Thanks: 2
Thanked 7 Times in 7 Posts
Default Re: Kohler 12 Res Natural Gas Gen OS fault

Yes, the butterfly goes full open when trying to start, the venturi in the carb helps develop the vacuum needed during cranking.

You could try checking for spark with an inline spark tester to make sure you have spark at both cylinders

Make sure you have gas flowing through the gas valve, the gas regulator on the gen has a removable plug on it, apply 12vdc to the gas valve & typically this would also be a great time to also hook up a gauge to read actual gas psi. Otherwise just check for flow.

Check your speed sensor on the opposite side of the engine coming out of the fan shroud will be a red & black wire, disconnect those wires & check AC voltage during cranking. Should be about 3.0 vac or higher.
Reply With Quote
  #5  
Old 05-08-2015, 08:46:51 PM
Trekrider2001 Trekrider2001 is offline
Registered-I
 
Join Date: May 2015
Location: Woodinville, Washington
Posts: 60
Thanks: 4
Thanked 2 Times in 2 Posts
Default Re: Kohler 12 Res Natural Gas Gen OS fault

Red an black wires measure 3-4 volts when cranking. I tried to remove the plug on the square box after the regulator (the one where you plumb for NG or LP). It is so tight, I fear I might break something if I force it. I don't have a gas pressure gauge anyway. Spark must be there because the engine "starts" and runs for about 1 second then shuts down with the OS fault code.
Reply With Quote
  #6  
Old 05-08-2015, 09:34:54 PM
Joe Batts Joe Batts is offline
Registered-II
 
Join Date: Jun 2009
Location: NJ
Posts: 57
Thanks: 2
Thanked 7 Times in 7 Posts
Default Re: Kohler 12 Res Natural Gas Gen OS fault

OS or overspeed means the engine speed is too fast (more than 3600 rpm). Just looking at this complaint, I would be concerned with if the engine is somehow getting stuck mechanically to go too fast or is there some kind of control problem doing it. If you try to run the machine by hand, can you keep it running? If you put a voltmeter that reads frequency on it across L1 & L2, is this a legitimate overspeed? Does it actually shut down at around 70 hz like it's supposed to? If it runs ok by hand, I would begin checking the stepper motor, 38.5 ohms across 1a, 1b & across 2a, 2b. Check pin connections at the controller, stepper motor plug, etc. If these check ok, we might start looking at a controller.
Reply With Quote
  #7  
Old 05-08-2015, 11:18:42 PM
Birken Vogt Birken Vogt is offline
Email NOT Working
 
Join Date: Sep 2009
Location: Penn Valley, California, USA
Posts: 2,201
Thanks: 2
Thanked 731 Times in 518 Posts
Default Re: Kohler 12 Res Natural Gas Gen OS fault

Another possibility is that the overspeed sensing part of the unit has gone flaky and is killing it right away before it can come up to speed.
Reply With Quote
  #8  
Old 05-08-2015, 11:39:24 PM
LWB250 LWB250 is offline
Registered-III
 
Join Date: Oct 2008
Location: Tampa, FL USA
Posts: 1,403
Thanks: 27
Thanked 438 Times in 379 Posts
Default Re: Kohler 12 Res Natural Gas Gen OS fault

I don't think you have a fuel problem, but just as a data point:

If you suspect a vacuum problem or a clogged vent/bad secondary regulator, remove the air cleaner and choke the mixer with your hand by covering it during cranking. This will increase the manifold vacuum substantially and help to open the regulator.

Dan
Reply With Quote
  #9  
Old 05-08-2015, 11:53:41 PM
pegasuspinto pegasuspinto is offline
Registered-III
 
Join Date: Oct 2006
Location: Floyd, AR, USA
Posts: 2,788
Thanks: 334
Thanked 1,324 Times in 859 Posts
Default Re: Kohler 12 Res Natural Gas Gen OS fault

+1 on getting a speed reading for real. In any case, over speed is a shutdown fault and there won't be any delay. That is why it quits. Either it is overspeeding or the control thinks it is.
Reply With Quote
  #10  
Old 05-09-2015, 12:02:42 AM
Trekrider2001 Trekrider2001 is offline
Registered-I
 
Join Date: May 2015
Location: Woodinville, Washington
Posts: 60
Thanks: 4
Thanked 2 Times in 2 Posts
Default Re: Kohler 12 Res Natural Gas Gen OS fault

Thanks! I'll try the hand choke in the morning. As to the over speed going flaky, where it that measured? Seems I would have to take half the thing apart to even get at the sensor.

---------- Post added at 09:02 PM ---------- Previous post was at 09:00 PM ----------

And I really don't think the thing is actually going overspeed. It barely has enough time to even start, let alone go too fast.
Reply With Quote
Reply

Bookmarks


Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

F o r u m Jump

Similar Threads Chosen at Random
Thread Thread Starter F o r u m Replies Last Post
Kohler Fault Shutdown Indicator Light Richland Kohler Generators 4 03-13-2015 11:18:05 PM
Kohler com6 over speed fault Dankariniemi Kohler Generators 6 04-22-2014 01:20:25 PM
Kohler model com6 over speed fault Dankariniemi Onan Generators 2 04-11-2014 03:00:23 PM
Kohler 10CC61 overspeed fault smokinyoda Kohler Generators 27 03-20-2014 04:18:48 PM
Kohler 10RY Throwing Fault Codes rdweninger Kohler Generators 20 04-04-2012 07:52:39 AM


Use "Ctrl" mouse wheel to change screen size.
All times are GMT -4. The time now is 06:10:40 AM.

Smokstak and Enginads site search!


All use is subject to our TERMS OF SERVICE
SMOKSTAK® is a Registered Trade Mark - A Community of Antique Engine Enthusiasts
Copyright © 2000 - 2016 by Harry Matthews P.O. Box 5612 - Sarasota, FL 34277