MEP-803A Troubleshooting Question - RPMs cycle after warm up

[mindshark]

I'm a new MEP-803A owner - GOVPLANET auction - 2002, 2669 hours. Bottom Line Up Front (BLUF): I did extensive pre- First Start maintenance. Followed the TMs for everything. The auction inspection noted that the fuel shut-off solenoid was sticking. I was, and I replaced it. Batteries, oil, anti-freeze (drained all, blew out line, vacuumed out tanks etc.)

Start-up. Followed start-up procedures and it started...ran well. No smoke and smooth idle. With one exception, all gauges working. Output at the lugs as set - using 120/240 setting. HOWEVER, frequency meter showed 55 hz. Ran the genny for 10 minutes...idled well. I attempted to adjust the frequency control knob...no change up or down in frequency.

At circa 15 minutes run time, the engine idle and hz started to climb...slowly up to max frequency gauge, then it dropped and the gauge settled back to 55 hz. (I did not further mess with the frequency control knob during this time).

I did find and fixed a small leak in the fuel hose going into the injector lines. (I'm going to replace all the fuel lines - probably there since 2002.) Once repaired, I went through the start-up again with same RPM surge/droop. The surge/droop cycle measured 55 seconds between 55 hz - 65+ hz and back.

I'm hoping someone has seen something like this before so I don't kill my wife's shoe budget doing repair by parts replacement. Thanks

 

[Ray70]

Welcome to the forum!
First off you should know that these machines are not designed to idle. they are intended to immediately start up at 60hz ( 61.5 without a load ) you should never idle them down.
Have you done any load testing at all yet?
Seeing that you could not raise the engine speed at all with the control knob I suspect you may have had 1 or more cylinders not firing correctly.
Perhaps that cylinder began to fire, increasing RPM and HZ, but then died off again??
A video would help diagnose what is happening.
I suggest you first confirm the speed control know id working as far as it pulling the throttle lever further open.
Then I would start it and again try to bring up the engine rpm to 1800 rpm ( 60 Hz )
If you still have no response from the throttle, try putting a finger on the side of the head below each exhaust port and see if you notice 1 or more cylinders that feel exceptionally cooler than the others.
And again... video is worth 100 posts!

 

[mindshark]

Good info. I’ll reply after following your great suggestions.

 

[rickf]

Did you adjust the frequency control or the small voltage knob on the control panel? What you needed to adjust was the engine speed, that sets frequency.

 

[mindshark]

Thanks for that. I did figure out the difference between the frequency control and voltage knob. I decided to inspect the frequency control under the 120v receptacle. I followed the TM to adjust it. Unlock, press button, turn. My helper turned it and I watched at the governor. I believe that cable is broken. No movement on the governor end. I’m going to remove it on the weekend for a full function check.

 

[Digger556]

Two thoughts:
1) If your control cable is broken, maybe the input to the governor control is moving around on its own, causing your fluctuating frequency.
2) There is a speed droop setting on the governor that makes it more or less aggressive to changes in rpm. If it's set too aggressive, it can cause the engine to "hunt" for a stable rpm.