MEP-002 problems

[GPrez]

Bought one of these last fall and messed with it briefly, but never got it to start. It turned over just didn't fire. Jumped back on it Saturday, and got it to fire. It idled nicely for a few minutes and then I disconnected one of the batteries to put back in my truck thinking it would run on it's own and it died. I immediately reconnected the lead before the motor completely stopped, but it still died. I tried restarting it with both batteries linked creating the required 24-volts, but it did nothing. After a few minutes I noticed the breaker at the 120V AC plugs was tripped as was the breaker on the control panel. I reset both, but the one on the control panel continues to trip every time I turn the switch to prime & run.

My first thought is perhaps the fuel pump is shorted out. Anyone else have a similar problem? Do the batteries have to be connected for these to run after they have started?

Does anyone know if these can be converted to 12volt like I did with my CUCV?

 

[mistaken1]

Did you download the TMs and read them?

I am not an expert by any means but I do know that idling the generator destroys the voltage regulator.

I do believe running the unit without batteries is not good for the charging system.

You would have to change the starter to 12V and the charging system to 12V and I assume (could be wrong) the generator field to use 12V. Someone who knows more will clarify.

 

[yamabro]

I think that would be more work than what it's worth. Any particular reason why you want to convert the gen to 12 v

 

[steelypip]

^^^
What he said. Download the TM and read it. Particularly read the operating instructions.

You can get TM-5-6115-584-12 here: Search for MEP-002A.

Operating instructions are on Page 1-2.1 (page 37 of the PDF). See also the instructions on page 1-5 (Page 43 in the PDF).

These sets are designed around the assumption that you will operate them exactly according to the TM procedure. Do it differently and get unpredictable results up to and including expensive component failures.

Yes, the set knows if the battery is connected - DC voltage out of range will cause a shutdown. So will excessive cooling air temperature or insufficient oil pressure. There's an automatic starter cutout, so you hold the switch in the start position until oil pressure has come up enough that the set will continue to run.

As (not)mistaken1 noted, running the set much below about 1500 RPM can push field current beyond the limits of the voltage regulator and fry its output transistors.

If this set has any value to you at all, read both the TMs. I likewise recommend you skim the LO and parts manual.

And Yes, I'm sure it would cost more than the cost of a second garden-tractor battery to convert it to 12v, if it's even possible.

 

[GPrez]

I think that would be more work than what it's worth. Any particular reason why you want to convert the gen to 12 v

No reason other than only needing one battery to hook up to it when I need to use it. It was more out of curiosity than anything else.


As for the idling of the set I wasn't idling at low RPM's. I can't verify exactly what RPM I was idling at but I did have the throttle pulled out so I don't think the voltage regulator was the problem, but I'll check it. It was only about a minute before I disconnected one of the batteries. Was thinking in terms of a vehicle with an alternator, I guess I can't do that.

I have a CD with all the TM manuals for all the generators the military used. I'll get it printed out. I was just looking for some quick answers from someone who might have had a similar problem. Now where did I put those reading glasses.

 

[Speddmon]

^^^
Yes, the set knows if the battery is connected - DC voltage out of range will cause a shutdown. So will excessive cooling air temperature or insufficient oil pressure. There's an automatic starter cutout, so you hold the switch in the start position until oil pressure has come up enough that the set will continue to run.

These sets have no idea if the batteries have been disconnected or not. The ill effects you will see if the batteries are disconnected have probably already been noticed by the OP. When you disconnect a battery while the set is running, the DC voltage spikes and can damage the DC voltage regulator and can damage the capacitors for the fuel pumps as well.

The easiest way to check to see if the fuel pumps are causing the problem is to unplug them one at a time and see if the DC breaker still trips. If you find one of the fuel pumps was the cause of the problem, unbolt the capacitor from the frame of the generator and cut if loose from the fuel pump and tie the wires together eliminating the capacitor...it's not a necessity anyway. That will tell you if it was the fuel pump or just the capacitor for the pump.

Once you get it running again, with BOTH batteries hooked up, check the DC voltage at the battery terminals, you should get about 28 volts +/-. If you are not getting above 24 volts then you have some DC voltage regulator issues, which I suspect anyway because the set didn't stay running when you disconnected the battery. The set should run on it's own without having any batteries hooked to it at all. The DC voltage produced by it's charging system will keep it running, but, like I said earlier it's not good to disconnect the batteries while it's running.

Do yourself a favor and do as the other above me have suggested, READ the TM's. I will go one step further and suggest an extensive searching and reading session on SteelSoldiers, because every symptom and guestion you have asked has been covered here before.

 

[PeterD]

... It idled nicely for a few minutes and then I disconnected one of the batteries to put back in my truck thinking it would run on it's own and it died...

Well, I do see two problems here:

1. Never ever idle a generator set. The regulator will try to create full output voltage, and at idle that is impossible. Result is that the regulator will burn out because it is trying to do the impossible.

2. Never disconnect a battery from a running engine. Doing so can damage the charging regulator, and other components.

 

[GPrez]

Thank you gentlemen. Hopefully my impatience did not do too much damage. I'll find out soon enough.

For the record Speddmon I did search this section before posting, but very little popped up. I'll try using different words and see what I find.

 

[Isaac-1]

Don't take it too personally, it is just every couple of weeks or so we seem to end up with a new MEP generator owner in here that has killed his new to him, most likely working generator by either idling it and killing the AVR output transistors or damaging the control/charging circuit by disconnecting the battery while it is running. You just had the bad luck to do both things. Maybe you got lucky and the damage is not too serious.

Ike

 

[Speddmon]

I'm not chastising you for asking questions. I'm simply saying, if you get an hour or so of free time search the site for general "MEP-002a" or "MEP-003a" threads and read them (or just scroll through the auxiliary equipment forum for posts). Most of them are people asking questions, and you can learn a GREAT deal by reading about other peoples mistakes/problems. I just helped gimpyrobb convert an MEP-114a over to a MEP-003a this past winter...he knew pretty much nothing about the generators beforehand, but he read every post he could find about them before we did the conversion and he ended up with a good deal of knowledge about his generator even before we put it together for him.

 

[GPrez]

I didn't take any of the comments personally. I've made mistakes before and I'll make them again, just not the same ones over again. Thanks for the suggestions Speddmon you are a wealth of information on these things from what I have seen. I did find a thread from earlier this year from a gentleman who after fixing his charging problem ended up with the same DC breaker tripping problem I am having, and he did the exact same thing to cause the problem (which made me feel better about myself ). He never posted the final solution so I PM'd him so that might help me narrow down my problem. Now I need to find some time to get back on it.

 

[GPrez]

Well I finally got back on it today, and got it running. Unpluged the fuel pumps till I found the guilty one and left it unplugged and it fired right up. It's producing 120V at the recepticals. I didn't check the 240V yet but I assume it is fine as well. I was so excited that I got it working that I forgot to check to see if it was pushing 28V at the battery connections as Spedmmon suggested, but I'll do that next time. It runs real smooth and the oil pressure came right up also.

 

[Speddmon]

good deal!! The fuel pump in question is probably good, I would remove the capacitor from it and see if it works or not. Probably will work just fine. The capacitor isn't really necessary on the fuel pumps anyway.

 

[steelypip]

Congratulations - You'll be very happy to have this handy beast sooner or later. I'm already paying attention to ads for cheap 3 phase welders...

One question for Speddmon - If the thing doesn't know if there's B+ or not, why did mine shut down when the jumper cables came loose during one test run? I know I get charging current both from the panel voltmeter and from battery state of charge after a run.

Maybe it was just a transient? Just curious. It was this even that lead me to believe that no batteries would result in a shutdown.

 

[Speddmon]

You can't really trust the panel volt meter at all, they are not terribly accurate. There is a procedure in the TM to test the charging circuit to make sure you are getting the full 6.5 amp charge. But I would guess that your voltage regulator is probably going south on you. I have one that sometimes charges and sometimes doesn't...just one of those things.