My first MEP generator (MEP-802a), oil pressure gauge not working

My first MEP generator (MEP-802a), new issue

Hi everyone! First off this site has been a wealth of info, as I'm just getting started with MEP generators and .mil surplus in general. So big Thanks to all the contributors out there!

I picked up a non-running MEP-802a off Craigslist for cheap. The previous owner indicated it had a broken master switch and a fuel leak from the tank area. All the pieces were present minus batteries, so I picked it up.



This unit is older with the plastic master switch shaft. I was able to fabricate a new shaft and save the switch. The fuel leak turned out to be the return line, which was broken at the tank fitting and on top of the engine. $15 in parts and some new batteries and she fired right up and got to work making electricity. I added a fuse to the A1 regulator and have a MOV on order.


Everything works except the oil pressure gauge. It is stuck at 50 psi and I'm not sure if it's the gauge or sender. Does anyone know what the ohm range is for the sender unit so I can test it?

Thanks!

Looks like a sweet deal if the hours are low and it works for you.Manuals.Everything you're looking for are in the manuals which Guyfang has gracefully placed in this forum.In other words I don't have a pat answer to your question, but am redirecting you to the source.Smart that you did the quad fuse and MOV mods.Look into making screens to cover the mouse entry ports (air cooling holes), it's a good investment.Good luck.

Page (PDF reader) 114 Paragraph 2-41.2 in the -24 TM to test the meter. Also make sure the wires are hooked up right.

Digger556 said:

Everything works except the oil pressure gauge. It is stuck at 50 psi and I'm not sure if it's the gauge or sender. Does anyone know what the ohm range is for the sender unit so I can test it?

Click to expand...

They are the US common 240-33 ohm variety.

Sounds like its time to replace all the return lines and possibly the fuel tank well nuts. How much did you get it for?

Guyfang said:

Page (PDF reader) 114 Paragraph 2-41.2 in the -24 TM to test the meter. Also make sure the wires are hooked up right.

Click to expand...

Doh!

Thanks. Meant to mention that. Wiring. Connections. ALWAYS assume first the connection is wonky, check for corrosion, missing wires, etc. I've replaced/repaired two wire connectors on my 802a already. Amazingly they didn't affect operation. One was from a sender by the dead crank switch on the side of the engine (it has a "spare" wire looped back and held down with a zip tie) one of the paired connectors bottom left side of photo, other was on the other side of the engine (it's been two years, I don't recall).

Vibration, heat, corrosion, metal fatigue, things wear out and/or break.

Reminds me of an Austin Healy Sprite I owned about 40 years ago. That car was a piece of... work... but it would nothing would ever wear out. Things BROKE long before you could run 'em enough to show any signs of wear. And don't get me started on Lucas electrics or I'll share horror stories of a Norton 850 Commando and Whitworth threads and breaking down near Tucson only to have a world-traveling pair of Brits on a Triumph motorcycle help me troubleshoot and find a loose connector in the headlight shell.

Wear and tear. It's part of the inspection list in the manuals.

NB

Guyfang said:

Page (PDF reader) 114 Paragraph 2-41.2 in the -24 TM to test the meter. Also make sure the wires are hooked up right.

Click to expand...

pjwest03 said:

They are the US common 240-33 ohm variety.

Click to expand...

Thank you both!

That is exactly what I needed. And thank you for helping me learn to navigate all these TMs

Bmxenbrett said:

Sounds like its time to replace all the return lines and possibly the fuel tank well nuts. How much did you get it for?

Click to expand...

$800 + $15 for fuel line and quad circuit fuse setup. The hour meter says 206 hrs on the unit. Judging by its condition, it seems plausible. The unit is very clean on the inside and nothing is missing. Given what surplus and Craigslist units are selling for, I'm feeling pretty good about what I paid.

Thats a great price. Nice steal.

Got the oil pressure gauge working. I threw a mechanical gauge on the engine and it registered 48 psi hot. The gauge in the panel was just stuck. Banged on it a few times and cycled it from 0 psi to running psi and it seemed to loosen up and start working properly.


However, I have load tested the generator a few times and the engine bogs down and wants to stall if I exceed 6000 watts resistive. I pulled the dipstick and there is some pressure on the crank case indicating blowby. The engine appears to be getting enough fuel as indicated by the exhaust. The exhaust plumbing looked good when I picked it up. Wasn't concerned about wet-stacking. ( I should disclose I live at 5200 ft. The nameplate derates the unit at 8000ft, but is it realistic to get full output (plus) at 5000 ft?)

That being said, I'm not sure what I should do with it now. I don't know how much of a problem the blowby is, although reading the forum, it sounds like a big deal.

Suggestions? I don't have much money into it, but I'm also still shopping for a MEP-803a.

Look in the TM for governor adjustment. Adjusting that should get you up to 7000-7500watts but that's about all she's going to do.

jamawieb said:

Look in the TM for governor adjustment. Adjusting that should get you up to 7000-7500watts but that's about all she's going to do.

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Understood, but still concerned about blowby. (should I be?)

If you take a typical 3% loss per 1000' of altitude you are going to be down about 15% in engine output in comparison to being at sea level.

The generator is RATED for 5kw. Sure you can dip into its over-design but its RATING is 5kw.

At sea level I can get between 6.5kw and 7kw out of a good running unit. As an example if we take 6.5kw and subtract 15% (~1kw) and you are down to 5.5kw - 6kw.

If you are getting 6kw out of your unit at 5000' I personally think you are doing OK. Run it as much as you can and see if the situation with the crank case pressure lessens.

Digger556 said:

My first MEP generator (MEP-802a), new issue

Hi everyone! First off this site has been a wealth of info, as I'm just getting started with MEP generators and .mil surplus in general. So big Thanks to all the contributors out there!

I picked up a non-running MEP-802a off Craigslist for cheap. The previous owner indicated it had a broken master switch and a fuel leak from the tank area. All the pieces were present minus batteries, so I picked it up.
View attachment 741199


This unit is older with the plastic master switch shaft. I was able to fabricate a new shaft and save the switch. The fuel leak turned out to be the return line, which was broken at the tank fitting and on top of the engine. $15 in parts and some new batteries and she fired right up and got to work making electricity. I added a fuse to the A1 regulator and have a MOV on order.
View attachment 741203
View attachment 741204
Everything works except the oil pressure gauge. It is stuck at 50 psi and I'm not sure if it's the gauge or sender. Does anyone know what the ohm range is for the sender unit so I can test it?

Thanks!

Click to expand...

Where is that sending unit for the oil pressure gauge located?

Its the round item hanging down from the T fitting near the dead crank switch. Number 7

While you are undertaking this troubleshooting, its a great time to add a manual oil pressure gauge to your machine, right at that T. Its been documented here on SS. I don't recall the thread, but I added one to my personal machine a number of years ago and its an excellent backup for not that much money (think the whole add on was like $75 or under).

Here is what it looks like in my machine.

That looks like a great idea!

Got everything working now, but there's no power going to the main panel where you hook up the leads. The 120 convenience receptical works, but not anything in the main box. I am a new 802A owner with an IQ around 60...lol...so maybe I am missing something...If I could make sense of the TM on these, I'd be a happy camper.

Have you flipped the AC Interrupt Switch to closed on the gauge panel? Thats how you tell the machine to send power to the lugs. If you have, does the bulb above the switch light up?

This thread is a blast from the past.

I'm up to 4 units now, haha