New to me PU798A (Mep-803a on a LTT-TQG high mobility)

[Daybreak]

Howdy,
The unit might have had some wet-stacking when I picked it up. It is all cleaned off inside and outside. The unit starts and works great with any load up to 133%

 

[AOR]

I have a question regarding the wet stacking. I am not sure how much my particular unit has wet stacked. It runs well without any smoke or soot. The issue I am now having is that when I put a decent load on it the generator will stall out.
I can run all of my shop lights and one ac unit which brings it to about a 50% load then when I add a second AC unit the engine will stall out. I can see some wet fuel on the side of the engine leaking from the muffler gasket. My good Mep803a units will run both AC units and all of the lights at about 80% load
I am planning to remove the exhaust manifold and check it out but my time has been limited. Any thoughts on my particular situation?

 

[DieselAddict]

I have a question regarding the wet stacking. I am not sure how much my particular unit has wet stacked. It runs well without any smoke or soot. The issue I am now having is that when I put a decent load on it the generator will stall out.
I can run all of my shop lights and one ac unit which brings it to about a 50% load then when I add a second AC unit the engine will stall out. I can see some wet fuel on the side of the engine leaking from the muffler gasket. My good Mep803a units will run both AC units and all of the lights at about 80% load
I am planning to remove the exhaust manifold and check it out but my time has been limited. Any thoughts on my particular situation?

The way to test for wet stacking is to add load a little at a time. Starting an AC unit is way too much load at once. You need to find that point where it struggles and hold it there till it clears then bump it up a little. 500w increments using space heaters is a good way to go. A load bank is even better if you can get access to one.

 

[87Nassaublue]

You got a sweet generator out of this deal. Gotta Love it!

 

[87Nassaublue]

Howdy,
OK, If my unit is the standard example of genset being sold.... you really need to do a 1-2 hour load test to clean out the pipes. I removed my muffler, and removed the exhaust manifold. I manually scrapped out the pathways in the head. Cleaned out the muffler as best as I could. Obviously the generator was run very lightly loaded in its prior life. When I pulled the exhaust manifold off, it was almost totally plugged with thick gooey carbon. I soaked the manifold overnight and then pressure washed it. Put it all back. Hooked it all up, started it up, and carbon flecks flew all over, ran a few minutes and then started loading it up. Got to 50% for about 15 minutes and the smoke just kept coming. Brought it up to 100% and it just kept smoking and black liquid dripping. After about 15 minutes here, the smoking was clearing up. I brought it up to 120% load, and it smoked some, but kept humming along. Stayed at 120% for 15 minutes, and then backed down to 75% load, now the exhaust is starting to clear up. Stayed here 30 minutes, went back to 120% for 15 minutes, sound and exhaust really looking much better. backed down to 75% 15 minutes, then down to 5% for a while. I then started turn things on and bouncing around with loads, the sound is much better, and now just a hint of smoke when a new load is added. I went up 25% at a time up to 125%. The whole generator is running smooth and not smoking like it first was. I gradually reduced everything back to 5%, opened the ac interrupter, waited a few minutes and then shut down. The MEP-803a is a very solid 10kw prime generator with a surge rating which I do not know the exact range, but it just kept running.
View attachment 556574
Halfway through at 120% load
https://youtu.be/FnWCyex-eGM

That thing doesn't even seem to struggle at all at 120% load.

 

[87Nassaublue]

By the book, 25% should be 1250 watts on a 5kw genset. That sounds reasonable to me to create enough load to keep heat building and pressure high. I don't think the manual would say to run at 25% based on loading it over it's rated running, when the max loading could vary.
You could put in a sensing circuit that switches on a 1300 watt device when normal load drops too low.

Ratch, can you tell me where you found that information? Normal math would indicate a 10 kw unit. I'd like to understand how they came up with that calculation.

 

[87Nassaublue]

Wet stacking has been a power generation problem for ever. The MEP-002 to MEP-006 sets had the same problem, if not worse. The military always allotted a generator much bigger then the job required. With good reason. Most units did not, could not and will never master, fingering loads. Most people have no idea how, and even when done right, it only takes one or two fools with a coffee pot and a microwave to spoil the figures. I once went to a communications site that had problems with the gen sets maintaining loads in the winter. After I took a pair of side cutters and clipped off the plug ends of four heaters, the problem went away.

Haa, it's something how you have to cut the wires to keep people from digging stuff out of the trash and putting it back into service. You should have also bashed the heaters with a hammer! LOL

 

[87Nassaublue]

I would take a picture for you guys, but now a days that is risky. The MP's and the security wiesel's like to find people who use a camera on post! Oh yeah, that got real interesting for me once in Bamberg.

Yeah, Andover, Ma. About 45-50 sets along with lots of trucks and trailers.

Well, then, you have to know about the place at the bottom of the steps that sells the Rauchbier! Man that was some good stuff!

 

[Haoleb]

I am picking up one of these same combinations this coming Wednesday.. All this talk of wet stacking makes me think I should check into that while I am giving it a once over. Now I am trying to figure out how I can load it up decently for an extended time. Most of my major appliances (except dryer) are gas.

 

[Daybreak]

I am picking up one of these same combinations this coming Wednesday.. All this talk of wet stacking makes me think I should check into that while I am giving it a once over. Now I am trying to figure out how I can load it up decently for an extended time. Most of my major appliances (except dryer) are gas.

Howdy,
Don't fret about it. You purchased the unit. The best thing you can do is prep it good, and run it loaded to make sure you have cleaned out the pipes. That should be done whether it shows signs of wet stacking or not. That way you know when you need to use it, it will work when you need it too.

Electric Oven? The electric oven, stove top etc, can be used to put a lot of load on too.

Best method
grab copies of all the TM's for the unit. Read them and understand the start-up procedure.
Have the normal replacement parts. Oil, Oil filters, fuel filters, fuel, batteries, meter to check voltages (besides gauges) proper wire, proper house interlock or another safe method for generator power to the house. While the unit is running, watch the engine compartment for leaks. Listen to the sound at no load, and loaded.

If the unit is similar to mine, the trailer is all aluminum. Take zip ties to mount lights. Make sure the brakes are released. Look under trailers forum and look at the height of the lunette, and pintle used for vehicle. Go prepared for airing tires, checking hubs for heat during travel, and check the unit a 1 mile down the road after recovery to verify it is all good to go.

There is a wealth of information here in the forums.

 

[Haoleb]

Thanks, it is very similar to yours but the trailer looks a little different. Luckily I should be able to just back right up to it with my CUCV and hook it on and go. Already got the pintle hook and the stock military trailer plug. And I am lucky I only have to go a few miles down the road to my house from where it is now on back roads. Definitely planning to go completely through it as you have before cranking her over. Once I get it i'll start my own thread to document the revival!

 

[Guyfang]

Thats a good idea. New thread. That way you, and us can focus on your set. When a thread gets to long, and has to many side issues, it makes it hard to remember just what the original problems were. Pictures help also.

 

[Ray70]

Hello everyone. I just joined the 803A family myself, picked up a pair of 803A's on trailers from Chambersburg PA last week. Got the both up an running very easily but after load testing them it seem I've got a few minor issue.
One unit runs great a loads up well to 75% however, when I remove this load and then apply a large motor start load ( 7.5HP air compressor) the gage will peg all the way up and begin to bog down. It does not trip the overload contactor. (Note: my Mep-003A will start this compressor with little difficulty )
The other unit will take about a 70% load then trip the overload ( although the light that comes on is the short circuit light not the overload )
So I'm assuming I need to first play around with cleaning the switch contacts, then measure the resistors for the overload relay. Then take a look to see if someone crossed the overload and short circuit light wiring? ( both units are Letterkenny resets ) Lastly I may have to investigate carbon buildup in the exhaust.
Any additional suggestions on why the overload would trip early on one and not trip at all on the other would be appreciated. Also, Battle short switch is in normal position. Not sure if I should try turning it on and retesting the unit that trips early to see how it reacts??

 

[Guyfang]

One unit runs great a loads up well to 75% however, when I remove this load and then apply a large motor start load ( 7.5HP air compressor) the gage will peg all the way up and begin to bog down. It does not trip the overload contactor. (Note: my Mep-003A will start this compressor with little difficulty )

Try loading this set up to 75% and letting it run several hours. Then bump it up to 80-85% and let it rip. Continue until it runs well at 115-120%. And let it run a while. See if that helps.


The other unit will take about a 70% load then trip the overload ( although the light that comes on is the short circuit light not the overload )
So I'm assuming I need to first play around with cleaning the switch contacts, then measure the resistors for the overload relay.

Assuming will get you in trouble every time! That doesn't mean you should not do the switch cleaning or resistor measuring. Just do not make up your mind as to whats wrong before you look into it some more.


Then take a look to see if someone crossed the overload and short circuit light wiring? ( both units are Letterkenny resets )

This doesn't sound right to me, but check it out. In fact, you may have a short circuit someplace. Dont assume!


Lastly I may have to investigate carbon buildup in the exhaust.

If you load it up the way I explained for the first set, you will not have to look into it. It will be done. Just start at about 60% with this one. Shorter load times the first two time, then let it run a while. See if it trips out again. If at all possible, use a resistive load. A heater or something like that.


Any additional suggestions on why the overload would trip early on one and not trip at all on the other would be appreciated.

See if the wires that are wrapped through CT2 are wrapped IAW the wire schematic. Have seen this before. Set trips out too soon, because the reading from CT-2 are false. But first load it up.


Also, Battle short switch is in normal position. Not sure if I should try turning it on and retesting the unit that trips early to see how it reacts??[/QUOTE]

Keep in mind, almost all safety features are bypassed with it is on. The use of the S-7 is to be carefully considered. First load the sets up, then go from there.

 

[DieselAddict]

+1 on everything Guyfang said. Until it will pull a steady 120% resistive load it isn't working correctly. High inrush loads like motor starts require a generator to be in top operating condition.

 

[AOR]

I currently have 4 Mep-803a units and I sold 2 others. Of the three good ones none of them will run my 7.5hp Ingersol Rand air compressor. When I tried the generator engine would bog down almost to the point of stalling but the compressor would not get up to speed to I did not want to damage anything so I stopped trying. I contacted IR and they said do not plan on a 10kw Generator running this compressor. . IR said we need a 65KW to run that 7.5hp compressor. We measured the amperage the compressor pulled on start up and for split second it was pulling 240 amps then it would drop down to 36 amps. We also noted when it was new in 2004 it was pulling 160 amps. It's possible your compressor is also pulling more juice to get it going as the capacitors get older and used more. Let me know what you find out on the other ones as I am having somewhat similar issues.

 

[JRM]

even my 2hp well pump pegs my 803 past 100% for a second

 

[Guyfang]

Are we talking about three phase compressors?

 

[DieselAddict]

I expect we are talking single phase which is a bigger challenge.

On the plus side they may be able to change the starting capacitor and/or put in a different unloader to reduce the starting power required. Those things are maybes though and would require some experimentation. At best I expect it to be 60/40 against it working.

 

[Guyfang]

What is it with the lack of three phase in the states? EVERYTHING here in germany is three phase. Makes it so much easier. And if you have a high start up amperage, you simply use a star/triangle start circuit.