Kohler 50RZGB Intemittent low speed

[DPeterik]

Model# 50RZGB s/n 2100715

This unit has an intermittent run issue. Once in a while during an exercise start the unit will start but only runs at 900-1000 rpms and then will shut down on "aux fault". But once it is reset it does not happen again for a while, and you manually start or test start from the transfer switch and it will start and run fine. A couple of weeks to a month later it will do it again.
This is a LP liquid system. The converter had leaked coolant and was replaced with OEM. Both fuel shut offs were replaced at the same time.
Mixer moves freely, mag pick up is good.
Have any of you Kohler techs come acrosss this before? If so any diagnostic tips. I only have the operators manual and wiring diagrams, no service or diagnostic manual.
If some one has a service manual for this I would apreciate it, as I have more of these units I service.

Thanks

Dave

[Jim Rankin]

electronic governor? I am assuming so from the mention of a magnetic pickup. Have you checked and perhaps removed and replaced all the connectons to the control board, throttle actuator and magnetic pickup?

When you exercise it does it pull a load?

[Mikey4026]

Does it have an external linkage from governor actuator to throttle lever?
I ran into a generator doing the same thing back when I was a service tech. The minimum throttle screw had fallen out, the throttle plate was sticking in the closed position and the governor could not overcome it. Putting in a new screw with a jamb nut solved the problem. I adjusted it to open the throttle just enough to prevent sticking.
Something easy and simple to check.
Regards
Mike

[EricWood]

Dave,

Those intermittent problems are a PITA to troubleshoot. Like intermittent driveability issues with cars.

Sounds like it doesn't come off of idle, when the event occurs. As Jim eluded to, I would start by inspecting the MPU for chunks of iron. May be flecks in there flying around, and randomly get stuck across the magnet, shorting it out, but rusty enough that the air turbulence of the flywheel teeth eventually blows them off. Check the ohms of the MPU, clean, readjust, and check MPU cranking voltage. Ohms should probably be anywhere between 180 to 250ish ohms. Cranking voltage should be in the ballpark of greater than 1.5 volts AC.

If MPU is clean, then perhaps the governor connections need looking at, or else the governor controller output drivers are failing. That will be a hard one to diagnose unless you can get symptom to repeat while you are there. I don't know if repeating numerous starts/stops would get it to occur for you while on site or not. Use two meters, one to monitor MPU voltage (AC), and the other to monitor actuator driver voltage.

Don't know if this has separate governror controller and actuator or not. Could be something as simple as Mikey mentioned, too. Also, if an integrated governor (such as a Woodward L-Series), check the butterfly plate for signs of that greasy, oily residue. Maybe sticky enough in cold weather to "glue" it shut momentarily, until vacuum breaks it free. The fact that it can only happen once, and usually after a period of sitting static, tends to make me think it might be something mechanical like this.

eric

[DPeterik]

This unit has an LC50 Woodward integrated controller/actuator. I have downloaded the software for this, but have to wait for the adapter harness, since Kohler did not install a RS-232 serial connector to the controller. I am going to reprogram it and monitor it as it runs under load.
I will let you guys know what the issue was with this.

[Mikey4026]

Dave

I suspect you may have an intermittent MPU signal, as the gen at least will start.
Once you get connected to the governor, the software will show you why it is not coming up to speed if you can create the problem. If you don't find any MPU problems look into the settings.
Setting up the L series can involve quite a lot of fiddiling, there are a lot of settings.
I would recomend looking at the settings on one of your other units and comparing them. Save a file from a gen that does not give you any trouble and flash it into the troubled unit if all else fails.

My information may not be totaly correct as I have not touched one in two years and am working from my feeble memory. Gunny can offer more information and can put you in contact with someone that is an L series wizard if all else fails.
Good luck
Mikey