MEP803a Rough Idle

[hooligan327]

First, I wanted to say thanks to all those who selflessly contribute their knowledge here. I'm pretty new to owning/operating one of these machines. I've had the genset for a couple years at this point but I just recently started using it to charge our off grid battery bank. It's been working pretty well. I have been charging our batteries at 10k watts which from what I've gathered is an appropriate amount of power to pull from this machine to avoid wet stacking issues. Recently it's been running rough when there's no load applied. This is especially true during cool down, but also happens sometimes at start up. The genset is outside and it's been cold. The genset is equipped with a hydronic coolant heater. When it's cold I run the heater for a couple of hours before I start the generator, usually the coolant is around 150 degrees when I start it. I keep the batteries plugged into the onboard battery tender when it's cold as well. I'll attach a link to a video of it running without a load. I would be interested in hearing thoughts on what might be going on here. Thank you in advance. https://www.youtube.com/shorts/BK1sCRliTNs

 

[Light in the Dark]

When was the last time you drained or changed out the water fuel seperator, or primary fuel filter? Do you filter your fuel before it goes into the machine, to remove excess water?

 

[hooligan327]

Changing out the fuel /water separator is on the list for today. It's currently -10 out there so I'm hoping it warms up a bit. I haven't changed it since I've owned it. I was told that it was new when I bought it. The fuel is filtered twice before it gets to the machine. I wasn't able to buy the cartridge fuel filter locally so I have to order it.

 

[Light in the Dark]

Well you might want to check your input feed lines for ice buildup too, especially when you note the issue often occurs with cold starts too.

 

[hooligan327]

Well you might want to check your input feed lines for ice buildup too, especially when you note the issue often occurs with cold starts too.

I'll take a look. Most of the time when it idles like that, it does it after it's been running for a couple hours, the batteries are full and the inverter is no longer loading the generator.

 

[Light in the Dark]

Well being a brushless head, there should be no mechanical reasons on that side (unless there is something failing... but you would know pretty quickly if so) so its probably air or fuel related. The beauty of diesels... only so many issues can cause poor running.

 

[hooligan327]

I just wanted to follow up on this. I finally got around to replacing the fuel filters and the air filter a few weeks ago. The water separator was a bit of a chore, as others have mentioned. I have a diesel-fired coolant heater (I think part of a cold weather kit) on my genset which offered interesting complications because it's mounted close to both the air filter and the two fuel filters. I did use a vice grip chain wrench which seemed to make the water separator part easier than anticipated.
After replacing everything the generator still has the same symptoms. After it's been running with a load on for a while and you open the contactor the engine surges (not sure if that is the correct term, see link to video in previous post). It will continue to do that if you reapply the load or if you shut it down and restart it. Any thoughts or suggestions are welcome. Thank you in advance.

 

[Ray70]

Very strange, it sounds like it's surging rapidly, like the governor droop setting is too sensitive, but I don't really see any swing on the Hz meter, unless the fluctuation is too fast for the gage to react??
I'd read the TM and look at the droop adjustment procedure, there's a hex key adjustment bolt inside the from timing gear cover that you access through a threaded plug near the throttle lever. You may want to investigate if your governor is oversensitive.

 

[hooligan327]

I guess that I should add. On a cold start, it starts and idles well. Also, when it was cold and I was using the engine heater on it, it also started and idled well,

 

[Guyfang]

Got to admit, never heard one like that.

When its running like that, show us a film of the L5, (Fuel Cut off Solinoid).

 

[Ray70]

I'm hoping that by "Idle" you mean running at operating speed, but at no load?
That is fairly Typical of a machine with an oversensitive governor. They do tend to start normally and run fine when "cold" then start acting up when they are at operating temperature. Usually you see the issue more predominantly if it's under a decent load and you disconnect the load, it then has a hard time stabilizing the engine speed and it hunts around, revving up and down slightly.
I assume your frequency gage is operating correctly? ( I once had one that would read up to about 60 than go no higher. Turned out there was a rectangular magnet ( possibly part of the assembly process ) inside the gage that was physically blocking the needle from going past 60Hz.

 

[hooligan327]

I ended up having to charge my batteries this morning. It took a bit more than usual to start the generator (it was 31 degrees out), but it ran flawlessly for 2 1/2 hours. Here is a video of it when the inverter disconnected and there was no longer a load on the generator. https://www.youtube.com/shorts/uWA3gJ97SxI

Also, I know that the temp gauge is not working, that just happened. I noticed that it stopped working after I had changed the filters. Maybe I bumped something or accidentally disconnected something, but I haven't had time to look into it. I have one of Kirk's autostart units on the generator and that still registers the correct temperature, so maybe it's just the gauge?

 

[Ray70]

Just a couple more questions, was there a load on the generator in the beginning of the video? If so, how much?
The load meter was reading zero and I could hear the same cyclical engine sound both before and after you hit the circuit interrupt switch.
Also, there was no change in HZ reading so I assume there was no load on it??
I was expecting the engine performance to change when you hit the circuit interrupt switch, assuming that was what you meant by disconnecting the load.
Or are you saying the engine performance changes when power is disconnected by the interuptor, even when there is no load on it?

 

[hooligan327]

Just a couple more questions, was there a load on the generator in the beginning of the video? If so, how much?
The load meter was reading zero and I could hear the same cyclical engine sound both before and after you hit the circuit interrupt switch.
Also, there was no change in HZ reading so I assume there was no load on it??
I was expecting the engine performance to change when you hit the circuit interrupt switch, assuming that was what you meant by disconnecting the load.
Or are you saying the engine performance changes when power is disconnected by the interuptor, even when there is no load on it?

There wasn't a load on the generator at the beginning of the video. At that point the batteries were full and the inverter stopped pulling power from the generator so there was no load on the generator at that point, the contactor was still closed (as you saw). For the majority of a charge cycle, the inverter is set to pull 10kw from the generator, for the last 20 minutes of the charge cycle the inverter is pulling about 5.5kw. I was going to take a video of the generator running with a 10kw load on it but like I said it runs flawlessly until the load is disconnected and then it starts running poorly. The generator will continue to run poorly if you reapply a load at that point. In fact if you reapply a load after it starts surging ( or whatever the correct term is for what it's doing) it runs really bad. Seems like it needs to cool down for a while before it will start and run well again.

 

[2Pbfeet]

There wasn't a load on the generator at the beginning of the video. At that point the batteries were full and the inverter stopped pulling power from the generator so there was no load on the generator at that point, the contactor was still closed (as you saw). For the majority of a charge cycle, the inverter is set to pull 10kw from the generator, for the last 20 minutes of the charge cycle the inverter is pulling about 5.5kw. I was going to take a video of the generator running with a 10kw load on it but like I said it runs flawlessly until the load is disconnected and then it starts running poorly. The generator will continue to run poorly if you reapply a load at that point. In fact if you reapply a load after it starts surging ( or whatever the correct term is for what it's doing) it runs really bad. Seems like it needs to cool down for a while before it will start and run well again.

Is it possible that you have an extra bolt/washer in the fuel cut off solenoid slide? The single bolt should move in the slot.

All the best,

2Pbfeet

 

[Ray70]

Is it possible that you have an extra bolt/washer in the fuel cut off solenoid slide? The single bolt should move in the slot.

All the best,

2Pbfeet

It probably has no effect related to his problem, but you're right, something is wrong with the way the FSS arm is bolted on.
Should be a single bolt ( usually with a black knob on the nut ) that's free to slide in the slot. That thing looks like it's got 2 bolts in it.
As long as the lever if full open when running it shouldn't cause the surging he's getting, but something definitely isn't right with the way it's mounted and should be investigated. Looks like a replacement FSS that's been put in it.

 

[Guyfang]

Spotted it too. And that might very well be the problem. For all intents and purposes, you are locking the Governor into one position. It can not adjust itself.

Look at these two documents.

 

[Ray70]

Spotted it too. And that might very well be the problem. For all intents and purposes, you are locking the Governor into one position. It can not adjust itself.

Look at these two documents.

I'm not following you... The FSS linkage doesn't move along with the governor / rack during operation, all it does is pull the "stop" lever out of the way inside the bock, allowing the governor to control the position of the rack.
He wouldn't be able to pull that 10Kw load if the governor was non-functional.
If the solenoid lever isn't able to fully open ( clockwise rotation ) the shut off lever, that will interfere with the governor and rack movement, but if lever can move fully clockwise the rack should work as intended.
Either way it needs to be corrected, I'm just not convinced that's his problem just yet.

 

[2Pbfeet]

I'm not following you... The FSS linkage doesn't move along with the governor / rack during operation, all it does is pull the "stop" lever out of the way inside the bock, allowing the governor to control the position of the rack.
He wouldn't be able to pull that 10Kw load if the governor was non-functional.
If the solenoid lever isn't able to fully open ( clockwise rotation ) the shut off lever, that will interfere with the governor and rack movement, but if lever can move fully clockwise the rack should work as intended.
Either way it needs to be corrected, I'm just not convinced that's his problem just yet.

Well, upfront, I know that you have way more experience than I do on these units. So take this as a dumb thought from someone new to these units, but here goes.

I believe that the reason for the slot in the linkage, rather than say a single bolt hole, is that the bolt onto the governor does need to move in the slot as the governor adjusts. I suspect that the extra bolt was put there to help fix governor so the unit could put out rated power. Since @hooligan327's unit is surging, and something isn't quite right with the governor control system, it occurred to me the bolt arrangement might be the cause. The flip side, of course, is that someone added the second bolt trying to fix some underlying and unsolved problem. Either way, I think that it would make sense to get the extra bolt out, and make sure that the single bolt moves freely in the slide, and see what happens.

Just my $0.02...

All the best,

2Pbfeet

 

[Ray70]

You guys are misunderstanding how that lever works. It's not part of the governor control system, it's the fuel on/off lever and only has 2 positions, full counterclockwise against the stop screw for fuel OFF and full clockwise against the other ( lower ) stop screw for fuel ON.
It does no move at all when the machine is running, regardless of what the governor is doing.
The reason for the slot is to allow the solenoid to fully retract when on and fully extend when off, without the lever causing it to stop part way through it's full range of motion. You will burn up the solenoid if you have power going to it but don't allow it to fully retract.
the solenoid has more "throw" than the lever does, which necessitates a slot for proper motion.