MEP-8xx fuel drain

[loosegravel]

I’m struggling with a retrofit fuel drain on these 800 series generators. I purchased some 3/4” bulkhead fittings with 1/4” NPT internal threads. The nut size for these bulkhead fittings is 1”. I also purchased some 3/4” ID neoprene flat seals and some 3/4” ID flat washers to back them up. The neoprene seals that I have are .125” thick. I’ve seen the retrofit kits and I’m just trying to buy my own parts to duplicate this retrofit. But no matter what I do, they leak. I’m using a neoprene seal and 3/4” ID flat washer on the inside and the outside. As soon as I tighten up the nut on the outside, the neoprene seal just squeezes out past the 3/4” ID flat washer. I’m open to suggestions

 

[Guyfang]

Read this thread.

Ultimate well nut repair

Thought I had a link to the washers. I dont see the harm in running a galvy washer personally

www.steelsoldiers.com

 

[loosegravel]

Read this thread.

Ultimate well nut repair

Thought I had a link to the washers. I dont see the harm in running a galvy washer personally

www.steelsoldiers.com

Thank you Guy. Someone is burning the midnight oil!

 

[kloppk]

You need a neoprene washer on both sides of the galvi washer that's on the outside of the tank.

Without the second neoprene washer fuel is sneaking under the outside neoprene washer via the threads, under the galvi washer via the threads and then leaking out between the outside of the washer and the flange of the brass fitting which aren't sealed. The additional washer will create a seal between the outside of the washer and the flange of the brass fitting.

You really should be using brass washers instead of galvi. There will be a galvanic reaction between the brass and galvi due to being dissimilar metals.

 

[loosegravel]

Wow! The above thread on well nut retrofits began back in 2017 and it's still growing! That's my problem I believe. I've been trying to use (2) 3/4" ID flat washers and (2) neoprene washers. (1) each on the inside and (1) each on the outside. When reading the super long thread though it appears that some are using a "nitrile" O-ring on the inside with no flat washer to back it up. I'm trying to lean on past experience for the best option. Someone wiser than me once said "you must learn from the mistakes of others, because you'll never have the time to make them all yourself." I have to agree.

 

[loosegravel]

Wow! The above thread on well nut retrofits began back in 2017 and it's still growing! That's my problem I believe. I've been trying to use (2) 3/4" ID flat washers and (2) neoprene washers. (1) each on the inside and (1) each on the outside. When reading the super long thread though it appears that some are using a "nitrile" O-ring on the inside with no flat washer to back it up. I'm trying to lean on past experience for the best option. Someone wiser than me once said "you must learn from the mistakes of others, because you'll never have the time to make them all yourself." I have to agree.

The other thing that has me confused is some of the photos in that thread are showing a metal surface on the outside where the neoprene washer seals. I thought that the 802's and 803's have plastic fuel tanks? That's what I'm dealing with anyway, plastic tanks where the well nut is recessed inside of a cut-out on the skid..

 

[loosegravel]

You need a neoprene washer on both sides of the galvi washer that's on the outside of the tank.

Without the second neoprene washer fuel is sneaking under the outside neoprene washer via the threads, under the galvi washer via the threads and then leaking out between the outside of the washer and the flange of the brass fitting which aren't sealed. The additional washer will create a seal between the outside of the washer and the flange of the brass fitting.

You really should be using brass washers instead of galvi. There will be a galvanic reaction between the brass and galvi due to being dissimilar metals.

Thanks for the suggestions Kurt. If I tighten the outside nut up against an additional neoprene seal, I believe it will simply distort it?

 

[loosegravel]

Thanks for the suggestions Kurt. If I tighten the outside nut up against an additional neoprene seal, I believe it will simply distort it?

BTW...they look like galvanized washers, but they're just the run of the mill zinc coated.

 

[kloppk]

Maybe use some RTV between the brass flange and the metal washer and on the threads under the outer washers.

 

[loosegravel]

Maybe use some RTV between the brass flange and the metal washer and on the threads under the outer washers.

I can certainly give that a try, thanks Kurt. One other interesting thing that I've noticed...at least while dealing with the 803A unit that I'm currently working on. The well nut hole is located very close to the bottom of the plastic tank, as it should be so that most of the fuel can be drained out. (I've found that I can remove the fuel drain well nut with 5 gallons or so of fuel in the tank by tilting the machine towards the opposite side of the fuel drain well nut opening) But it's located close to the curvature of the radius, so close that I'm wondering how anything could seal it up on the outside?

 

[kloppk]

... I'm wondering how anything could seal it up on the outside?

I guess thats why they used the original well nut. It would conform to the radius. It makes it's seal with the bore of the hole itself in the plastic tank as it expands.

 

[loosegravel]

I guess thats why they used the original well nut. It would conform to the radius. It makes it's seal with the bore of the hole itself in the plastic tank as it expands.

That was my guess also.

 

[Daybreak]

Not all bulkhead fittings are the same.
A proper A3816 nitrile well-nut works fine. Don't over tighten and split it.
The correct 1/4" Brass Bulkhead Fitting (Includes Viton O-Ring) works fine.

There are many options out there. The 2 items work. If you use something else, and have problems. That is on you.
The threads cover all the pertinent info
Fuel Tank Well Nut A-3816 info also Added pointers to Ultimate well nut repair