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Kohler 20RZ - HELP! - Electronic governoer RPM loss after unit warms up.

Adaptel

Registered
I have a 2003ish Kohler 20RZ generator that I picked up used about a year and a half ago for use at my home where I have frequent power outages. It had 220hrs on it, has a Ford 2.5 propane engine, DEC 3+ controller, propane fueled, RS-485 serial remote annunciator, and connects to my main panel with an ASCO transfer switch. Before I installed it, I went over it top to bottom, replacing head gasket, timing belt, PCV valve, plugs, wires, oil, & coolant. This generator has served me EXTREMELY WELL since I have installed it, but last week I was outside while it was going through its bi-monthly exercise run and it sounded strange. I popped the control panel and noticed that the freq meter was bouncing around 40-50hz instead of rock-solid at 60 where it had always been. I was busy and thought I would look at it later.

Well, last night I lost my power, the generator kicked in, and everything in my house powered back up within 30 seconds. After about 10 minutes, the power kicked off again, came back on for about 10 seconds, went off, and was cycling like that constantly. I ran downstairs and killed the main breaker to prevent damage to my electronics. Well, the generator was once again running too slow.

My unit is the newest revision of the 20RZ and in addition to the DEC3+ controller, it has the fully electronic speed control system where a electric solenoid controls the throttle plate. I have reproduced the problem several times now and am scratching my head. If I let the unit completely cool down and fire it up, I get perfect voltage and Hz (measuring exactly 1800rpm using a digital timing light). Once the unit warms up, the RPMs start falling off slowly and if I let it run for 30min, they will drop as low as 900-1000rpm. I have checked my propane supply/pressure which is rock solid at 10.5inH20, put a scope on the magnetic pickup and the signal remains clean and steady while cold and warm......but cannot figure out why this is happening!?!?!?! I can manually move the throttle arm and get the engine to come back up to speed but have no idea where else to check next. Bad solenoid? Bad governor controller?

I don't want to randomly start throwing expensive parts at this problem and if anyone has suggestions of what to check next, it would be GREATLY APPRECIATED! Does anyone know of any documents that cover the electronic governor troubleshooting in detail? Thanks in advance.
 

Isaac-1

Registered
Last Subscription Date
01/12/2014
My gut feeling would be drop out on the magnetic pickup, but you say you put a scope on it, so I am not sure. Did you check for drop out on the ignition side? Also does the electronic speed control try to keep the throttle wide open when it looses speed, or is it closing it making the engine slow down?
 

Adaptel

Registered
My gut feeling would be drop out on the magnetic pickup, but you say you put a scope on it, so I am not sure. Did you check for drop out on the ignition side? Also does the electronic speed control try to keep the throttle wide open when it looses speed, or is it closing it making the engine slow down?
I suspected the magnetic pickup at first too, that is why I carefully watched its output from when it starts up cold and runs ok, to when it warms up and starts to slow down. The signal is rock solid in both conditions. I have also used my timing light to watch for missfires on all four cylinders, and the spark is solid too (I can easily detect a misfire with the digital rpm meter on my timing light).

When the engine starts losing speed, the throttle is definately not wide open but just the opposite. The actuator starts slowly closing the throttle and I can bring the speed back up by manually moving the throttle arm open again. Do you know what kind of signal controls that actuator? Is is voltage controlled or Pulse-Width-Modulation? I guess the next step would be to watch the signal being fed to the actuator to see if it doing what the controller is commanding, or if the controller is sending the actuator bad data.

One other thing I thought was strange. I don't know much about Ford EDIS ignition, but under normal operation, my timing light indicates 1800rpm when connected to the 3 cylinders closest to the front of the engine. Strangely, when I put the clamp on the cylinder closest to the alternator, it reads 3600rpm. Is it normal for only one cylinder to be generating a "wasted spark" and the others not?
 

Adaptel

Registered
UPDATE: I decided to perform a vacuum test by putting a vac guage on the intake manifold. I am not sure how this relates to the governer, but the one thing I do know for sure is that I have a problem with the engine....most likely in the head/valvetrain. Even when cold and running at 1800rpm, the vacuum needle is bouncing violently between 38 and 52kPa. I am assuming that I have sticking valves or worn guides which gets worse as the engine warms up. I have a really good machine shop locally and was thinking of pulling the head and having it rebuilt because something definately is very wrong. Is my thinking sound? Opinions?
 

Vanman

Subscriber
Last Subscription Date
07/10/2019
Is the throttle holding steady while the manifold pressure is fluctuating? Or is that electronic governor causing it?

Keith
 

Adaptel

Registered
I wanted to post to say that I did get this problem sorted out and my 20RZ is now working perfectly. It proved to be a lesson in buying a used piece of equipment and how you can never know the quality of work that has been done on it in the past. The vacuum test problem told me that I needed to tear down the motor and find out why the intake manifold vac readings were fluctuating so wildly. Well, someone had obviously taken the intake manifold off in the past and when they reinstalled it, they had the gasket crooked and punched two of the bolts through the gasket. The gasket became brittle and sections of it on cylinders 1 & 4 had broken free and were missing. These missing pieces likely got ingested into the engine. Problem #1 was that I obviously was dealing with an intake manifold leak.

I took the head off and cyl4 was caked in oil and there was actually a blob of oil hanging between the gap in the spark plug (I am assuming this is why I was getting a weird double-rpm reading on my timing light on this cylinder). I took the head to my local machine shop and I had bent exhaust valves on cylinders 1 & 4. They also said that the oil seals on all the valves were quite dried out and have lost their flexibility. I had them do a complete valve job including replacing the bent valves. While I was waiting for the head to be rebuilt, I decided to remove all the cylinders, hone the bores, and replace the piston rings. Bent valves & bad oil seals = Problem #2.

While the engine was completely apart, it allowed me to see something that was hidden. Behind the intake manifold, there is a large grounding point with about 5 wires bolted to the block. It had lots of corrosion on it. I traced these wires and one of them went to the electronic governor brain box that controls the throttle actuator solenoid. I cleaned all these connectors and coated them with anti-corrosion goo. Bad grounds = Problem #3.

So, I am happy to report that my 20RZ is good as new and running better than it ever has before. I have run it for 5 hours and it stays at a rock-solid 1800RPM and puts out a perfect 60Hz voltage. Thanks for your helpful input.
 

Isaac-1

Registered
Last Subscription Date
01/12/2014
I am glad you have your problem sorted, and thanks for the update for the rest of us.
 
I wanted to post to say that I did get this problem sorted out and my 20RZ is now working perfectly. It proved to be a lesson in buying a used piece of equipment and how you can never know the quality of work that has been done on it in the past. The vacuum test problem told me that I needed to tear down the motor and find out why the intake manifold vac readings were fluctuating so wildly. Well, someone had obviously taken the intake manifold off in the past and when they reinstalled it, they had the gasket crooked and punched two of the bolts through the gasket. The gasket became brittle and sections of it on cylinders 1 & 4 had broken free and were missing. These missing pieces likely got ingested into the engine. Problem #1 was that I obviously was dealing with an intake manifold leak.

I took the head off and cyl4 was caked in oil and there was actually a blob of oil hanging between the gap in the spark plug (I am assuming this is why I was getting a weird double-rpm reading on my timing light on this cylinder). I took the head to my local machine shop and I had bent exhaust valves on cylinders 1 & 4. They also said that the oil seals on all the valves were quite dried out and have lost their flexibility. I had them do a complete valve job including replacing the bent valves. While I was waiting for the head to be rebuilt, I decided to remove all the cylinders, hone the bores, and replace the piston rings. Bent valves & bad oil seals = Problem #2.

While the engine was completely apart, it allowed me to see something that was hidden. Behind the intake manifold, there is a large grounding point with about 5 wires bolted to the block. It had lots of corrosion on it. I traced these wires and one of them went to the electronic governor brain box that controls the throttle actuator solenoid. I cleaned all these connectors and coated them with anti-corrosion goo. Bad grounds = Problem #3.

So, I am happy to report that my 20RZ is good as new and running better than it ever has before. I have run it for 5 hours and it stays at a rock-solid 1800RPM and puts out a perfect 60Hz voltage. Thanks for your helpful input.
Why do you suppose you had bent exhaust valves? if the motor jumps time does it bend the valves?
 
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