Ultimate well nut repair

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Daybreak

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Howdy,

An explanation;
The well nut leaks over time, age, eaten by military JP8, over tightened, or dry tank, or a shortcut taken to drain the MEP-803A fuel tank by yanking the drain out.

On the MEP-8xx generators you have 2 piped fittings on the fuel tank. 1 is on top for the fuel return line. 1 is for the drain line. The MEP-802A fuel drain inside the engine compartment below the oil drain valve. The MEP-803A has the fuel drain external along the bottom of the skid.

The unit uses a A3816 brass nut covered in nitrile rubber which is installed from the exterior. The pipe fittings screws into the unit and causes the rubber to squish out and seal the hole. The problem exist with the 40 inch/lbs torque. Go to tight and the rubber splits.

The 1/4" brass bulkhead fitting with viton seal is used in the rest of the world, especially in boating. A fuel cell with no leaks is absolutely mandatory in a boat. The bulkhead fitting passes that requirement.

The bulkhead fitting is exactly what Boatman69 calls this thread. Ultimate well nut repair. Something which should be a standard fix for the generators. It might take a little more doing, as you need a piece to be on the inside of the fuel tank. Creative ways will come to light probably thru this thread.

Some more picture are needed with the part together, and taken apart. With pictures of the washer, and where and why needs to be filled in.

A parts listing of all pieces to have on hand to complete the job.
 
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rogpike

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Kentucky
Thanks, I read some more about that after I read some of these posts. Was about to order 2 of the well nuts yesterday evening but went outside to check my genset. I was in the dark with a flashlight, but I could not find the thing (either of them) anywhere in the 803a. Do you have to remove something to see it? I am sure it is one of those things like my mom used to say (if it was a snake it would have bit you....meaning I was looking right at it).
 

Guyfang

Well-known member
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Rogpike,

We are going to have to work you up to speed on the -24P.

When in doubt, always check the -24P. Figure 17, Item numbers, 36, 37, 38. Page number, (PDF page number) 64.

Yeah, at night you need to know what you are looking for. You can find one of them, easy. The other, you need X-Ray eyes!!
 

rogpike

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Rogpike,

We are going to have to work you up to speed on the -24P.

When in doubt, always check the -24P. Figure 17, Item numbers, 36, 37, 38. Page number, (PDF page number) 64.

Yeah, at night you need to know what you are looking for. You can find one of them, easy. The other, you need X-Ray eyes!!
What I figured. Have not had time to read any manuals yet. I have however read a ton of forum posts.
 

boatman69

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So I started thinking about my 831a. No leaks but I was wondering about the well nut. And I'll be darned if lo and behold they come with the correct part I spect for the other generators. Imagine that!
 

robson1015

Member
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Location
New Concord, Ohio
I would love to see a detailed description with pictures of the tank fitting install. Complete with all parts needed and how everything goes together. I still have the rubber well nuts on my unit but eventually I know I am going to need to replace both. I have a pretty good idea of how this new well nut should work but alot of us still have questions about install and adapter needed etc....
 

Triton

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Location
Houston, Texas
I want to do this fix so I am collecting the parts, what fitting do I need to go to the bulkhead fitting? If I am reading this right I need a 1/4 inch npt male to a 5 AN male fitting, is this correct?
I love bullet proofing my 803!!!
Thx
 

Zed254

Active member
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South Hampton Roads, Virginia
Boatman69 indicated in post #1 that all you needed was the fitting with the O ring and a 3/4" flat washer. His pic shows the brass nut hiding the 3/4" washer, I believe. The O ring should be inside the tank sealing the fitting against the plastic fuel tank. It appears that Boatman69 did not need to purchase any additional fittings: it looks like he used what was on the machine that attached to the original well nut. At least that's the way I understand the installation.

Check out post #1. Follow the link to the fitting. Then click on the Technical Drawing.
 

Triton

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What got me started on this was his post #12, it led me to believe I need to get that fitting. I got the bulkhead fitting in today just want to get all the parts before I start. I did find out that there is no -5AN fitting
 

Zed254

Active member
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South Hampton Roads, Virginia
https://nationalstocknumber.info/part-number/MS51500A4-4S_008377073

From TM *ARMY TM 9-61 15-641-24P
AIR FORCE TO 35C2-3-456-14

I started looking for the well nut. A3816. That takes you to the parts for Figure 17.

40 PAOZZ PAOZZ 96906 MS51500A4-4S .ADAPTER STRAIGHT PIE 2
TO TUBE

So item 40 in Figure 17 on page 63/148 (pdf file) is the fitting you are interested in. Do a net search on item 40's part number MS51500A4-4S and you get the above link that describes the fitting. This is the fitting that is installed in the Well Nut of your MEP-802A.

I think you can re-use this part and the adapter will function as described in post 1.

Image is the wellnut I replaced on my 802. It shows the fitting in question.
 

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