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Kohler 20RZ surge/hunts at startup


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  #1  
Old 11-05-2018, 12:49:09 PM
Zephyr7 Zephyr7 is offline
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Default Kohler 20RZ surge/hunts at startup

I’m thinking this might be too high gain on the speed controller, but since it’s a bit of a PITA to get to that thing I thought I’d seek the wisdom of the forums first.

Here’s the deal: one of my two 20RZ gensets just showed a screwy issue for today’s exercise run: it would hunt a LOT right after startup. Then settle down, then hunt a LOT. It kept doing this for maybe 5-10 minutes and settled down when it got up to operating temperature. Voltage was pretty stable the entire time, but frequency was in the 55-65 range during the hunting. You could see the actuator on the throttle crank it open and then swing back a forth a fair bit (way more than the normal small jitter) while it was doing the hunting/surging.

I’m thinking the gain needs to come down a bit on the speed controller but it seems odd to me that it got more stable and settled down completely when it warmed up all the way. This is an NG unit and the block heater is failing so it’s starting cold (I’m guessing outdoor ambient temp so around 50* today).

Any ideas of things to check besides fiddling with the gain? I don’t see any loose connections or chewed wiring. This unit has been solid for about two years since I found the squished plugs that were causing misfires before.

Bill
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  #2  
Old 11-05-2018, 01:18:50 PM
LWB250 LWB250 is offline
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Default Re: Kohler 20RZ surge/hunts at startup

I would check the regulator vent to see if it's obstructed. Governor gain settings don't change or drift significantly over time, it's most likely a fuel system related issue.

Dan
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Old 11-05-2018, 01:29:06 PM
Zephyr7 Zephyr7 is offline
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Default Re: Kohler 20RZ surge/hunts at startup

Regulator vent is clear. Engine sounds ok when running. Iím thinking about checking the mag pickup since Iíve seen them get weird before they fail in the past. The only thing strange to me this time is that it gets ok once it warms up which makes me think mechanical.

It has been pretty wet and rainy the past several days. Maybe just something was damp? I did check the air filter though and that was fine, and dry.

Bill
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Old 11-06-2018, 03:56:39 PM
Zephyr7 Zephyr7 is offline
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Default Re: Kohler 20RZ surge/hunts at startup

I ran the unit again today and it did the same thing several times. I canít find any mud dauber gunk in the regulator vent (although they did fill up some unusued bolt holes on the engine castings), and nothing seems chewed, damaged, or clogged. I popped off all the spark plug wires to see if I had any bad connections and they all look clean without carbon trails. Hmm.

I opened up the control cabinet and backed off the gain a bit, maybe one position worth on the pot so itís maybe 1/3 from the car counterclockwise position. That seems to have stabilized things. Iím going to have to check things with my manometer when the weather is better. Today is rainy and quite windy so I just wanted to get things working quick.

The strange thing is it did stabilize when it came up to operating temperature (maybe 7-10 minutes or so), which doesnít sound like a regulator issue. I was thinking maybe some moisture condensed somewhere due to the weather, but the early runs should have dried things out so that I wouldnít see the issue on later runs but it made no difference.

Throttle linkage all seems to be solid.

Bill
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Old 11-06-2018, 04:00:51 PM
I like oldstuff I like oldstuff is offline
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Default Re: Kohler 20RZ surge/hunts at startup

Are you sure it's not too lean? Can you fatten it up a bit to see if that helps?
*Dry fuel engines also can surge if too rich. Just mess with the mixture and see if it improves.
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Old 11-06-2018, 04:15:47 PM
Zephyr7 Zephyr7 is offline
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Default Re: Kohler 20RZ surge/hunts at startup

Quote:
Originally Posted by I like oldstuff View Post
Are you sure it's not too lean? Can you fatten it up a bit to see if that helps?
*Dry fuel engines also can surge if too rich. Just mess with the mixture and see if it improves.
I have to check the procedure to adjust the mixture on this unit. I think itís the big spring loaded screw on the right of the throttle assembly but Iím not 100% sure. I tried moving that screw about 1/4 turn either direction while the unit was running poorly and it made no change. I also need to check supply side gas pressure with my manometer.

The only thing I know changed is that the block heater no longer keeps it reliably hot. The block heater seems to work when it gets really cold out (below freezing), but not at all when itís warmer than that. It used to keep the engine around 80-100 all the time. And I can say that the unit has run reliably without the block heater since the block heater quit early this year and weíve run on generator a few times since.

Bill
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Old 11-06-2018, 04:35:57 PM
Birken Vogt Birken Vogt is offline
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Default Re: Kohler 20RZ surge/hunts at startup

Check the timing also.
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Old 11-06-2018, 05:31:09 PM
Zephyr7 Zephyr7 is offline
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Default Re: Kohler 20RZ surge/hunts at startup

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Originally Posted by Birken Vogt View Post
Check the timing also.
Do you think the timing being of could make a problem that would be pretty bad cold and gone when warmed up?

The unit doesnít even have 500 hours on it so I never thought to check the timing belt. I suppose someone before me could have messed with it though. I bought it used.

Bill
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Old 11-06-2018, 05:48:08 PM
Birken Vogt Birken Vogt is offline
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Default Re: Kohler 20RZ surge/hunts at startup

These units did like to jump timing belts but I never heard of one that did and still ran at all.

What I meant was ignition timing. I have found it advanced or unstable leading to speed regulation problems more than once. Open up the distributor and see if the head of the shaft is stable inside the bushing and all that.
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Old 11-06-2018, 06:36:40 PM
Zephyr7 Zephyr7 is offline
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Default Re: Kohler 20RZ surge/hunts at startup

Quote:
Originally Posted by Birken Vogt View Post
What I meant was ignition timing. I have found it advanced or unstable leading to speed regulation problems more than once. Open up the distributor and see if the head of the shaft is stable inside the bushing and all that.
This is one of the newer units with the electronic ignition module. As far as I know, it has no adjustments at all. There must be a crankshaft position sensor somewhere, I could check that. Iím thinking itís up in front somewhere hard to get at. Whomever designed the belt guard on this thing didnít think too much about accessibility. I was really glad I had my extra long 1/4Ē extension bars when I replaced the thermostat. Some of the fasteners on the guard are pretty hard to reach.

Bill
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