The infamous Well Nut info

Daybreak

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Howdy,
Take a look at the pictures. The well nut is actually a nut assembly covered in rubber (nitrile in our case)

You have a hole in the plastic fuel tank. The fuel line has a threaded fitting on it, these threads reach the nut assembly on the far side of this little well nut. When it starts compressing, kinda like a rivet, it smashes the rubber out to the sides and seals the hole. This is also where folks get in trouble. They want to make sure it is tight. That is when that extra turn makes the rubber split, and you have to start all over. These well nuts are encased in nitrile rubber, the fuel line pipe threads is what they are saying to put a little form-a-gasket 2. Obviously fuel rated Teflon tape works too.

When the well nut starts to squish.. yes it has a tendency to turn the whole assembly. I was able to put a large flat blade screwdriver on the edge of the large washer and a little of the well nut edge to hold it until it tightens and grabs the hole.

Remember 40 inch pounds... it really does not seem like its tight, but, mine are all holding. (used a small craftsman, inch-pound torque wrench)
A-3816 nitrile well nut 5.jpgA-3816 nitrile well nut 4.jpgA-3816 nitrile well nut 3.jpgA-3816 nitrile well nut 2.jpg
 

Daybreak

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Howdy,

I am happy to help the community with the extra A3816 nitrile well nuts I had purchased. I am glad I was able to get them out for a decent price.

I did not realize they ____________ were moving the well nuts along for $20.70 each. wow... aua

:-D
I am sold out.
 
Last edited:

Daybreak

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Howdy,
I do not have any more well nuts.

I can only say, you need to verify that the sleeve material is made out of Nitrile (buna-n) You can find well nuts all over. But, since this is in contact with diesel fuel, you need the correct material.
 

Haoleb

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I am looking at replacing my non leaking (yet) fuel drain well nut on my 803. Maybe it is obvious but not to me, It seems like everyone removes the fuel tank to install a new one? Seems to me I should be able to just get the old one out, clean around the hole inside and out then just install the new one from the outside. Am I missing something here?
 

Haoleb

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Daybreak

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Thanks, I did see that one but the 803 is a little different, the fuel drain is on the outside in the skid area. Seems like I could just put a socket or crows foot on there and tighten it down no problem.
Howdy,
Do NOT do that!
That will make it split.
The MEP-803A uses 2 A3816 well nuts. The fuel drain is external which you can easily see. The same principal applies about tightening. Yes, if you have a leak, you will want to drain all the fuel out of your unit. Loosen the fuel drain well nut, and it should come right out. Clean around the hole, and with your fingers and rag, right around the inside of the whole too. Place your new well nut in position and tighten to the SPEC 40 inch-pounds. You done.

The MEP-802A has the well nut fuel drain inside kinda under the oil drain valve. If you look inside your 803, you can see the little cut out notch. The lower header is used on both the 802 and 803. That notch is where you would find it on a 802.

Neither unit needs the fuel tank removed for replacing the well nut.

Both units use a well nut on the top of the tank. That one is accessed when you take the front panel off to get too. If you have the front panel off, you can replace the fuel return line there, and check the well nut for over-tightening, or age.

Re-read the thread and PS mag article too.

I believe if you need a A3816 well nut, you should contact member Chrispny.
 

dav5

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Howdy,

OOPS.
Hi Mike, I just got home with my 803 [not the one I won unfortunately] I haven't had time to give it a once over but for sure the wellnut for the fuel drain is pulled out. Luckily I have a wellnut for the top of the tank. Do you know if it is the same one for the drain line? Do you know what sealant goes on the threads? Would you advise adding some silicone in case the tank hole has been damaged?
Thanks again for all your info.
 

lurch44

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Dav5
The well nut is the same for the top sending unit and the bottom fuel drain. I had just gotten replacing mine. I bought 2 from GMG. Just remember 40 inch pounds.I just wiped out the inside of the hole.
 

NormB

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I got lucky.

Was replacing the batteries the other day (Optima yellow tops - prior owner put in some cheap garden center tractor batteries about a year old now - genset would start, take an hour to recharge. Optima? Starts FASTER, recharged in less than ten minutes), got to thinking about the lower well nut and saw the "cutout modification" on the frame had already been done for me. I'd bought a couple of the seals last summer when I bought the generator as it seemed like a good idea at the time.

Don't need to replace 'em right away, but it's like the superstition of not expecting a fire 'cause you have a fire extinguisher in your truck (two, actually, for more "insurance"... now that I think of it, I NEED one for the generator, too).

Thanks to everyone who's posted/updated this thread.
 

Daybreak

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Howdy,
The MEP-802A and MEP-803A use the same 2 well nuts. Guyfang also added that the well nuts are used on the larger units as well.

A-3816 well nut with nitrile rubber sleeve.

The only location for a tiny dab of sealant would be on the threads only. The well nut goes in the hole, and the pipe then starts screwing into that which starts to squish the well nut which closes and seals the hole. The area around the hole just needs to be clean.

The well nut is used around the fuel drain and at the fuel return line in top of the fuel tank.
 

Daybreak

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Howdy,

When the folks drain the units, sometimes they take a shortcut and yank the fuel drain plug out. You might even be able to save the well nut. Simply hold the well nut, and turn the fuel pipe to take it off. Put the well nut back in place and put the fuel pipe piece in and tighten. 40 inch pounds...
 

Another Ahab

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Howdy,

When the folks drain the units, sometimes they take a shortcut and yank the fuel drain plug out. You might even be able to save the well nut. Simply hold the well nut, and turn the fuel pipe to take it off. Put the well nut back in place and put the fuel pipe piece in and tighten. 40 inch pounds...
So, it sounds like the threads of the well-nut actually cut INTO the pipe piece (unthreaded) as it twists into place, is that the mechanics of it?
 
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