MEP-114A GPU

Guyfang said:

Then there is no need to fool with the Main gen and excitation system. Or not?

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If i had to guess, the AC from the wires im pointing at(which are doubled onto the wires going to the main connection terminal) goes into the 28vdc control box and is stepped down…

I'd say that's the case

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Thats what it looks like to me. You might even get the maintenance manual and schematics from Hobart. But thats not something I have ever seen.

So you are still going to need the main gen to provide voltage to the Hobart box.

Well it's good to keep in mind the overall list of things to do first things first we need to get the engine stable

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Well the filter canisters were deff nasty, water inclusion and stuff, only the rear pump is working, easy options for jut removing them and going to a more readily available shelf item that functions the same? Also, best gasket replacement for the canister lip?

There are off the shelf options available that will function however tearing the existing pumps apart and cleaning them cost you maybe a couple hours of time a drop in replacement fuel pump can run in the hundreds. If your dead set on just replacing them let me know when you want to do with the old ones I would gladly take them.

The last time I did fuel filters I used wix filters and they came with the square cut gaskets

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Scoobyshep said:

There are off the shelf options available that will function however tearing the existing pumps apart and cleaning them cost you maybe a couple hours of time a drop in replacement fuel pump can run in the hundreds. If your dead set on just replacing them let me know when you want to do with the old ones I would gladly take them.

The last time I did fuel filters I used wix filters and they came with the square cut gaskets

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So the one that isn’t running, if i take it apart and clean it then it should work again? That has literally never happened to me with fuel pumps haha. I have gasoline sitting in the filter housing overnight to help clean it.
On another note, how important is the bus fuse on the back of the alternator?

azreark1 said:

So the one that isn’t running, if i take it apart and clean it then it should work again? That has literally never happened to me with fuel pumps haha. I have gasoline sitting in the filter housing overnight to help clean it.
On another note, how important is the bus fuse on the back of the alternator?

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Of all the sets I've worked on that had that model of fuel pump I think I've only had one that was not salvageable.

I recently cleaned up a set for a friend that were so varnished up I had to use high pressure compressed air to blow the Piston out of the pump, and once everything was cleaned it worked like a champ.


Somebody designed to fuse there for a reason so if it were me I'd continue using it. If I had to make a guess I'd say it was more for alternator failure back feeding.

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No Bus fuse, no battery charging. The set runs on 28 VDC, so if the battery charging alternator is non op, and the batteries are low, what do you think will happen?

Be advised that running this gen set long periods without sufficient loads, will cause Wet Stacking like you have never seen before.

Guyfang said:

No Bus fuse, no battery charging. The set runs on 28 VDC, so if the battery charging alternator is non op, and the batteries are low, what do you think will happen?

Be advised that running this gen set long periods without sufficient loads, will cause Wet Stacking like you have never seen before.

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So when i very first got it running, the charge voltage was one of the first things i checked and it showed like 34vdc, i had to manually turn down the output to like 26v. I have a feeling the alternator needs to be replaced since even after lowering the output it had voltage creep past the regulator.

So you know how the saying goes about the lowest bidder? This is the kind of crap from a mechanic of the lowest bidder...


Something wrong with this picture...see the color? lol i was surprised to see it that bad especially since we're in the desert


And thank you so much for the pointer about pulling the whole fuel system apart, changing the filters was on my list but i probably wouldn't have gone into the separator and pumps if yall hadn't said anything. Have the pump that wasn't running apart and the inside looked about like this picture of the separator bowl



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Do not forget the Day tank. And when its out, test the FL-1 and FL-2 on the float switch.

Been there and done that with a full fuel system take down and cleaning. But if you skimp, there is always, at least for me, the thought that I don't KNOW if its clean the whole way through. And in the old days, if I did not come home smelling like diesel, my wife would have thought I was out fooling around.

This could be an air leak too. We saw it often it Patriot. Mechanics did not take the time to LOOK/FEEL when hooking up these lines. Good find. This looks like the line to a fuel pump to me.

Yeah i think youre right for it being an air leak source, and also correct on the location, that is from the fuel selector to the first pump.
So cleaned out everything, new filters and it will run. Remember that IDLE/RUN toggle on the front i told yall about? Well it will change the rpm from low speed to operating speed so not sure what thats about, its also finnicky and i will have to toggle it up and down sometimes to keep at operating rpm. When running and start switch held and Voltage/Amp knob on L1-L0 i get 120vac on the genset gauge, toggle CKT BRKR switch to CLOSE and i get 120v on each leg measured at the main connection point, HTZ gauge reads 0 though, will that only show a reading when its outputting a load?
When it cools down im going to pull the head off the injection pump and see how it looks since it seems to be hunting up and down a little…might also be because theres no load? Give me some input on that one.
Going to throw some diesel cleaner in the tank, just for piece of mind for the long run.
Regulator in alternator is shot i think, at operating rpm the output is 32vdc and i have the manual voltage adjuster on it turned all the way down.
The front side fuel pump was bad, tore it down, cleaned it and tried to test it straight from the battery and nothing, even tried beating the shit out of it and no joy, rear pump works great though and is currently installed all by itself. Yall know the approximate working fuel pressure this should be at? Probably going to a COTS option entirely.

Now on to the 28vdc box. The tag says Input is 3-phase, 200v, 400htz so i switched the genset to L3-L1 which gives me 200vac on the gauge but no reading on the hobart box for DC input.

Just for some misc info, unit has 820hrs and got it for $500. Add 2 new batteries, new filters, and a handful of cans of brake cleaner and seems (at least for the AC genset side) i have a good running generator.


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The frequency gauge should be before the output contactor so it should indicator frequency even if the main contactor is off. I would avoid idling this set the avrs are not very happy with low frequency. I've never played with the 400 Hertz gauge however I know the 50 60 hertz gauges are known for malfunction so you might just have a bad gauge

So…what can i plug into this other than a coffee maker(from a previous post lol) that incan test without burning it up, any ideas? Haha


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azreark1 said:

So…what can i plug into this other than a coffee maker(from a previous post lol) that incan test without burning it up, any ideas? Haha


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Pretty much anything without a motor would be the general blanket statement.

Heaters and incandescent light bulbs really don't care about frequency. If you're talking about stress testing this thing you're going to need a lot of load.

Yeah i don't think i have access to anything but an airplane that could actually stress test this unit.

azreark1 said:

Yeah i don't think i have access to anything but an airplane that could actually stress test this unit.

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I built a heater for my 004 which consists of three water heater elements that I just submerge in a tank of water. Without factoring in the frequency you would need about six to put close to a full load on this thing

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So the GPU box is a Hobart TR-1528, snagged a manual and was going through it. The panel is missing a switch so referenced the manual and viola, its the main contactor switch...well thats a good place to start on why there's no DC output from the box haha.