MEP-114A GPU

Hello group, my partner snagged a MEP0114A GPU for me to fix and get running (was retrofitted with a 28v DC starting unit for aircraft by Hobart for probably the Air Force, the Hobart tag has a contract and NSN number). He purchased from an airport FBO that had it sitting in their boneyard for a few years because "it didnt work anymore" and that was about all the information they gave me on it. I slapped two new batteries in it, it will start up but struggle a little bit, like there's no fuel pressure/fuel flow.
Low pressure oil light is lit on the main panel, i plumbed a gauge in to the engine to verify pressure and there's 60psi at idle. I couldn't hear the lift pump running with switch in RUN, so applied 24v directly to it and it will sluggishly run but wont make a difference on how the engine runs, my next step is to change both filters since i don't know how old they are, but i'm wondering is the Low Oil Pressure fault trying to kill the engine? Running in Battle Short doesn't change how it runs.

So that's problem number one, getting it to start and run consistently, problem two is no generating juice. When i move the operation switch from IDLE to RUN, it doesn't always rev up to operating RPM so i'm thinking the switch needs to be replaced? Will test that later, but it is a Mode II genset so it's all controlled electronically.

I'm trying to dig into the manual but it's a lot and my partner(he's a business guy, not a mechanic) wants this thing operational ASAP, but at a minimum wants it properly diagnosed as soon as possible, so i want to come to all of you in the community with way more experience in the genset for help, rather than comb over the manuals for options that may or may-not actually fix or help fix the problem. I have a regular full time job and this is on the side so can't really spend my whole day combing through manuals and testing.

So for now, two things, consistent start/run cycles and genset field excitation. It's an old military diesel so theoretically, as long as that injection pump has fuel flow that engine should run top notch (and when it's running, the thing sounds mint)

Oh and the airport FBO we bought it from decided it needed to be white (i guess back when they bought it) and removed the data plates on the outside of the MEP unit, so all i have is the engine tag.

EDIT: Thanks for helping me with the 114A identification.

Low oil will come on when the unit is placed in run (no pressure). After you start it flopping the reset switch should reset the fault light.

I would start with fuel. Filter condition and possibly gummed up pumps

Now that I've had more caffeine, there are 2 fuel pumps plumbed in series. Then the water seperator and primary filter. This goes through a solenoid valve to a tank then the 2nd filter to the injection pump. To get the pumps to run without the engine, switch the set to run and the battle short to on. You should hear some clicking(the clicking should be asymmetrical, if you hear just a steady click(similar to a ticking clock) it's likely only 1 pump is contributing to the flow))(fast if there's fuel flow, slow if it's building pressure). Ideally if you haven't opened anything up in the system slow clicking. Open the drain for the water separator and the clicking should speed up. There's a good chance your pumps need cleaned out (don't worry they are easy)

If you are having starting issues and it seems to be starving of fuel I would look at the 2nd filter and check the check valve on the injection pump. Did they leave all the diagram plates inside the doors?

Are you running from the set tank? Or Aux fuel?
Have you downloaded all the TM's from the TM forum here in SS?

Like Scoobyshep has told you, start with the fuel system. If its been sitting a long time, I would not screw around. Order two new filters and take the fuel system apart. Clean in from start to finish. Including the Day Tank. Take the E-Pumps out, tear them apart and clean them good. Use something to take the diesel lacquer off the parts. Make sure the pumps run well, by hot wiring them on the work bench. Make sure they are the RIGHT pumps. Lots of pumps LOOK the same, but are not. This is not rocket science. A few hours work and you will KNOW its right. At the end of the day, this is the only way you can feel safe that its done, and done right.

There is NO IDLE to this set. It is supposed to run, loaded or unloaded, at its rated speed. If you have no output, then you should have no reading on the hertz meter?

, but i'm wondering is the Low Oil Pressure fault trying to kill the engine? Running in Battle Short doesn't change how it runs.
No, the oil pressure has nothing to do with engine speed or smoothness.

the operation switch from IDLE to RUN, it doesn't always rev up to operating RPM so i'm thinking the switch needs to be replaced?
There is no idle. So what position are you talking about? Switches rarely go bad.

but it is a Mode II genset so it's all controlled electronically.
This is a rare bear. Not a lot of sets were made. If it is a Mode two, then its NOT a MEP-005A. Its a MEP-104A. Very scarce. Probaly only members in the forum are LuckyD and I, who have ever seen one.

So for now, two things, consistent start/run cycles and genset field excitation. It's an old military diesel so theoretically, as long as that injection pump has fuel flow that engine should run top notch (and when it's running, the thing sounds mint)
Lets just start with getting it to start and run. Excitation can wait. Also, if you do not hold the S2, (Start Switch) up in the start position long enough, the gen set will NOT make power. So once it hits operating speed, hold it a few seconds longer.

Take a picture of the Electric Governor and Magnetic Pickup. It would be nice if you took one shot of the data plate on the E-Governor, so I can see the part number. Take some other shots of the inside. Maybe we can see something you cant.

Scoobyshep said:

Now that I've had more caffeine, there are 2 fuel pumps plumbed in series. Then the water seperator and primary filter. This goes through a solenoid valve to a tank then the 2nd filter to the injection pump. To get the pumps to run without the engine, switch the set to run and the battle short to on. You should hear some clicking(the clicking should be asymmetrical, if you hear just a steady click(similar to a ticking clock) it's likely only 1 pump is contributing to the flow))(fast if there's fuel flow, slow if it's building pressure). Ideally if you haven't opened anything up in the system slow clicking. Open the drain for the water separator and the clicking should speed up. There's a good chance your pumps need cleaned out (don't worry they are easy)

If you are having starting issues and it seems to be starving of fuel I would look at the 2nd filter and check the check valve on the injection pump. Did they leave all the diagram plates inside the doors?

Click to expand...

They left the diagrams, all they did was paint the outside, interior is still OD Green. So with direct power the pump towards the rear(control panel) runs, but the front(towards radiator) does not. Bought new filters today so will test that. With start switch in RUN and BATTLE SHORT-ON, neither run.

Guyfang said:

Are you running from the set tank? Or Aux fuel?
Have you downloaded all the TM's from the TM forum here in SS?

Like Scoobyshep has told you, start with the fuel system. If its been sitting a long time, I would not screw around. Order two new filters and take the fuel system apart. Clean in from start to finish. Including the Day Tank. Take the E-Pumps out, tear them apart and clean them good. Use something to take the diesel lacquer off the parts. Make sure the pumps run well, by hot wiring them on the work bench. Make sure they are the RIGHT pumps. Lots of pumps LOOK the same, but are not. This is not rocket science. A few hours work and you will KNOW its right. At the end of the day, this is the only way you can feel safe that its done, and done right.

There is NO IDLE to this set. It is supposed to run, loaded or unloaded, at its rated speed. If you have no output, then you should have no reading on the hertz meter?

, but i'm wondering is the Low Oil Pressure fault trying to kill the engine? Running in Battle Short doesn't change how it runs.
No, the oil pressure has nothing to do with engine speed or smoothness.

the operation switch from IDLE to RUN, it doesn't always rev up to operating RPM so i'm thinking the switch needs to be replaced?
There is no idle. So what position are you talking about? Switches rarely go bad.

but it is a Mode II genset so it's all controlled electronically.
This is a rare bear. Not a lot of sets were made. If it is a Mode two, then its NOT a MEP-005A. Its a MEP-104A. Very scarce. Probaly only members in the forum are LuckyD and I, who have ever seen one.

So for now, two things, consistent start/run cycles and genset field excitation. It's an old military diesel so theoretically, as long as that injection pump has fuel flow that engine should run top notch (and when it's running, the thing sounds mint)
Lets just start with getting it to start and run. Excitation can wait. Also, if you do not hold the S2, (Start Switch) up in the start position long enough, the gen set will NOT make power. So once it hits operating speed, hold it a few seconds longer.

Take a picture of the Electric Governor and Magnetic Pickup. It would be nice if you took one shot of the data plate on the E-Governor, so I can see the part number. Take some other shots of the inside. Maybe we can see something you cant.

Click to expand...

Thats a lot of good points. Some diesel injection pumps will pull past INOP pumps so wasn't sure if that applied to this model. So this is the problem with getting something second hand, the IDLE-RUN switch i'm talking about looks like its the LOCAL-REMOTE switch in the manual, IDLE and RUN is how previous owners have labeled it.
Scrolling through the forum today i did learn about holding the switch in START to excite the system, so at least now i know that.

azreark1 said:

They left the diagrams, all they did was paint the outside, interior is still OD Green. So with direct power the pump towards the front(control panel) runs, but the rear(towards radiator) does not. Bought new filters today so will test that. With start switch in RUN and BATTLE SHORT-ON, neither run.

Click to expand...

For everyone's sanity, the radiator is the front and the control panel is the rear.

These fuel pumps are extremely simple and I highly recommend you take them both out apart and clean them. You typically can run on one BUT that's if they are the correct pump. There's a flow through and a non flow through model. The look the same but one will not allow fuel to flow if it's not running. The correct pumps are flow through.

If you are replacing filters (you absolutely should) you need to take a good hard look at all of the system. I recently got a set that lost an injection pump due to fuel contamination. When I found evidence of water intrusion into the secondary fuel filter is when I took a closer look at the entire setup. I found that the water separator had been plumbed backwards rendering it completely useless. So I always look now I don't trust what others have touched in the past.

azreark1 said:

Thats a lot of good points. Some diesel injection pumps will pull past INOP pumps so wasn't sure if that applied to this model. So this is the problem with getting something second hand, the IDLE-RUN switch i'm talking about looks like its the LOCAL-REMOTE switch in the manual, IDLE and RUN is how previous owners have labeled it.
Scrolling through the forum today i did learn about holding the switch in START to excite the system, so at least now i know that.

Click to expand...

Do something quick for us to help eliminate further confusion. Look at your hertz gauge. What's it's reading range? Around 50-60 or is it closer to 400?

Engine wise it doesn't change much but if it's in the 400s then this set is fairly useless unless you're working at an airport

Scoobyshep said:

Do something quick for us to help eliminate further confusion. Look at your hertz gauge. What's it's reading range? Around 50-60 or is it closer to 400?

Engine wise it doesn't change much but if it's in the 400s then this set is fairly useless unless you're working at an airport

Click to expand...

It is a 400hz unit, and yes we are at an airport. The usefulness of the 28vdc 1000amp starting power is the end use of the unit, there is no planned usage of the AC generation power.

Ok. Thanks for clarifying, engine wise not much changes but electrically it makes a difference. As Guy pointed out, this is not a 005a but a 104a.

Sent from my SM-S908U using Tapatalk

Then its not a Mode 2 set. Its a MEP-114A....................... If its 400 hertz, its a MEP-114A

So the only thing you want this set for is its 28 VDC charging system?

Guyfang said:

Then its not a Mode 2 set. Its a MEP-114A....................... If its 400 hertz, its a MEP-114A

Click to expand...

Damnit I fat fingered it..

As soon as I saw airport, I knew its was a MEP-114A. I can tell you some real funny stories about 400 hertz equipment.

Guyfang said:

As soon as I saw airport, I knew its was a MEP-114A. I can tell you some real funny stories about 400 hertz equipment.

Click to expand...

I can imagine, motors running at 6.667x rated speed

Not long!

I worked in the Hawk/Patriot ADA world, for the best part of 20 years. We were 400 hertz.

Guyfang said:

Not long!

Click to expand...

But exciting!

In a duck and cover kind of way

One good thing about it, the coffee pot worked well on 400 hertz. The Missile systems used 416/Three Phase. On the radars there was a 120 outlet, but it was 400 hertz. So we always had hot coffee in the field, without having to run a five or ten KW. Ooooooooh how a drill could run!!

Guyfang said:

So the only thing you want this set for is its 28 VDC charging system?

Click to expand...

Yep only to start airplanes, that's it.

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