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.

 

[rickf]

Unlock and turn. The button disconnects the mechanism and is used to quickly push in to idle. Not something you want to do in this machine. So, turn counterclockwise to increase speed/frequency and clockwise to decrease. Do NOT use the button Once you have it set then turn the lock.

 

[mindshark]

Thanks so much to each of you for your sage inputs. Here's a quick update...after adjusting the set screws on the governor (they were totally unscrewed) and inspecting the frequency control cable, I'm confident that the frequency control setup works. Adjusted the Hz to 60 Hz on start up. Warm up, stayed at 60...then started cycling RPMs after about 5 minutes of warm up. As Ray70 suggested, I broke my mind and figured out how to post a video on this: https://www.youtube.com/shorts/U0DQdK6eLVg. Hollywood has nothing to worry about, but I think it does well demonstrating my quandary. I even figured out how to get closed captioning-old guy new tricks. Hope this looks familiar to someone so I can get an azimuth to pursue.

 

[mindshark]

Guess attacking the governor image where the frequency control cable connects w/the adjustment screws before I followed the dash 24 for adjustment might be of interest.

 

[2Pbfeet]

Glad to see you made progress. See post #6 above by @Digger556 about the "hunting" behavior, and adjust the governor per the the TM.

All the best, 2PbFeet

 

[Ray70]

The video is great, it really shows your issue in detail. The "cycling" you have going on is definitely not your typical governor droop out of adjustment, it's very odd how RPM's slowly increase, then abruptly drop right to 60 then repeat.
When the droop is adjusted wrong it will be more of a smooth rapid cycling up and down.
BUT.... I would still try adjusting the governor droop and see what happens.
It definitely seems governor related, it's just not what we normally see!
Good job with the video!

 

[Digger556]

After watching your video, I suspect something in the fuel rack, governor flyweight assembly, or injection pump(s) sticking or catching.

It's acting like the engine is getting slightly too much fuel, slowly increasing in rpm until there is sufficient force to "pop" the rack loose. Then it snaps back to nearly the correct fuel rack setting, and then the process starts over.

In your video, is the generator under load or not?

 

[mindshark]

I appreciate your thoughts. I was thinking the same. Frankly, the rack and metering pump problem is scarring me. I’ve seen a few vids, studied the TM, gone through some good posts here, but I feel like a pig starring at a watch.

At this point, I haven’t used a load. Essentially trying to get it to run first.

Separate, all the fuel lines were weeping. Cracks, eye. I replaced them, ran up the machine with good results…surge remains, but the moisture is gone.

 

[Digger556]

I appreciate your thoughts. I was thinking the same. Frankly, the rack and metering pump problem is scarring me. I’ve seen a few vids, studied the TM, gone through some good posts here, but I feel like a pig starring at a watch.

At this point, I haven’t used a load. Essentially trying to get it to run first.

Separate, all the fuel lines were weeping. Cracks, eye. I replaced them, ran up the machine with good results…surge remains, but the moisture is gone.

Fuels lines are notorious. Funny, my oldest 1994 unit had the least issues with lines, the newest 2011 had the worst line cracking.

The governor and fuel rack linkage are a little complicated, but not terrible. I would review the TMs, pull the front cover and exercise the linkages. You may need to pull the IPs one at time to verify none are sticking.