In Tank FI Pump Solutions?

[Max Welton]

Someone on the type-3 list posted this:

http://blef.org/vw/t3/fueltankvent.jpg

And I snagged one from Joel Mitchell.

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Max

[Max Welton]

There's a problem with the Holley unit when used on the bottom of the tank. It leaks.

The foam, which sealed fine initially, started to leak. What happened was that the foam did not maintain the compression over time. Here's what it looked like today when removed.

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Here's how it looked originally:

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To be honest, I think the foam might also have squished down if used on the top of the tank. But it wouldn't have leaked liquid gas. If anything it would have leaked fumes.

I'm not done with this idea. Ordered this guy along with some an8 fittings. Should be able to mate it up with the Holley pump and Hydramat.

https://www.amazon.com/gp/product/B088T ... le_o00_s00

Max

[Max Welton]

Given the limited access I think I'll use zip-ties to attach the pump to the rod next time.

Not very good at waiting ...

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Max

[Max Welton]

Well the new pump hanger is in. Nice piece. But too big.

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I'm learning now that the 12-bolt pattern is a "standard" for such things. Is there also a standard 6-bolt pattern? Looking ...

Max

[Bruce.m]

The foam gasket looks to be neoprene or something like that. If the flange is fairly flat, perhaps you can cut out a replacement gasket from Viton rubber sheet?

[Max Welton]

Yes. I'll also modify the clamps so they can pull the hat down a little farther. Right now they can only get to about 4mm.

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That's the short-term plan. But the Holley hat has some other weaknesses I want to address.

Long term I have a line on a fresh tank that we can do some metal work on to flatten out part of the center bump (depression? ) to create a larger flat area so I can use the 12-bolt plate.

So this first effort will be considered a prototype. I love the Hydramat pickup and the pump so will keep those.

Max

[Max Welton]

While I'm working on getting a fresh tank, I'm trying to make this Holley hat to seal.

For new seal material I got some of this:
https://www.napaonline.com/en/p/FPG3045

Then I took some material off the dogs so they would pull the hat down (up?) farther to work with a thinner seal. To get some thickness, I made two seals to stack. I put it all together and put a quart or so of fuel in the tank. No leak. I'll check it again in the morning.

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Max

[Max Welton]

Didn't work. I think this material isn't soft enough to seal unless the surfaces are absolutely perfect.

I have some nitrile bonded cork and also some NBR on the way to try.

Stay tooned!

Max

[Ol'fogasaurus]

Max, have you tried the old way of checking for flatness?

Set some sticky paper and put it on the underside of the opening you are having fun with, this is to seal off any crap that could come into the tank.

Next spray a light coat of "machinist bluing" over the area giving you problems. Next take a straight flat file laying it flat and using the file with each end your hands lightly do cross-strokes over the area changing the direction on each stroke (this is to be sure you are not putting too much filing in one area). It shouldn't take long to find if and where any high or low spots could be.

It is an old trick, so I am posting it for what it is worth.

Lee

[Bruce.m]

I’d have gone with a small sheet of Viton rubber easy to get on eBay in thicknesses of 1mm and up.

[Max Welton]

The NBR arrived. It's around 1.25mm thick and very flexible. Came in a 12"x12" sheet. To get the thickness I want I stacked three layers.

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Lee, I was worried more about tiny scratches and such than flatness. But I'll remember the trick with the bluing. Thanks!

So what I've done is scruff the sealing area with a wire wheel and apply a skim coat of that seam-sealer I used before. Dries impervious to gas. It will grab only the first layer of the NBR so I can still remove the cover. Gonna let this sit for a while so the seam sealer can dry.

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Max

[GS guy]

Max, I fear the fuel tank metal thickness is too thin to stay flat while being clamped by the 5 dog clamps. It likely warps a little at each clamping spot when tightened, providing a wavy surface the gaskets can't fully seal to. You might try fabricating a metal ring matching the hole ID and hat OD from 1/8" (3/16"?) thick steel, with a slit along one side to fit it inside the tank - providing a stiff plate to "sandwich" the thin fuel tank metal and help spread out the dog-clamping load? You're gonn'a have to keep that tank sealing surface pretty darned flat while clamped to ensure a good seal!
Jeff

[Max Welton]

And leak it did. Right away too. Even with only moderate pressure.

The 12-bolt cover has a ring as you described. I'm still working a deal for a fresh tank to modify.

Max

[Ol'fogasaurus]

Perfection is expensive and time consuming. On drawings there are allowable variances for both dimensions and angles.

When bending/forming metal (metaphoric) you stretch and compresses the metal and the lighter the weight of the metal the farther away from where the actual work is being done the material can also deform a certain amount.

The "Doubler" idea that the GF guy has a good idea assuming it can be done. Template time is in order!

If I remember correctly, the vapor of fuel can get pretty thin depending on several things. https://www.caranddriver.com/news/a1533 ... explained/

Lee

[GS guy]

I presume you looked at the Tanks, Inc. offerings when selecting the replacement cover/fuel pump mount? This one looks like a smaller diameter version, might be about the same as the Holley hat?
https://www.tanksinc.com/index.cfm/page ... prd227.htm

Not sure if they sell the mount/hat portion separately? Might be worth asking. Adapt your existing pump, etc.
Alternately, making your own custom feed-through plate (like the blank hole cover you installed earlier) with the necessary fittings, etc might be the way to go? If you go that direction I would move the electrical feed-through to the top of the tank somewhere, just keep the plumbing on the bottom.
In any case, sandwiching the tank surfaces seems to be the tried and proven method to get a good seal. We're rooting for ya!
Jeff

FWIW - I see the Tanks Inc technical section has a 6-hole gasket drawing. Might provide some useful info?