Another fuel tank plumbing option

[nkemp]

If there's no need to remove the cover for the hole where the old fuel pump used to be, one could simply RTV a piece of plastic to it.

Farrar

I think one can assume that one would need to get into the tank again. For example the pump may fail (will over long enough usage) and need replacement.

So the issue is finding or making a tank pump hole cover. At this point I'm pondering a fiberglass cover molded to the original top portion of the boot to seal the tank. I'm not sure how well the two would bond or how well they would bond using Polyurethane or similar. It would be attached to the tank with a hose clamp like now and thus could be removed to be serviced. BUT I still hope for a better idea.

Nick

[LEVY]

.

How about one piece of metal with a gasket for the outside (round) with a hole in the middle. For the inside, a "T" shaped rod with thread on one of the legs. You insert this T inside the tank with the tread facing up, this threaded rod will go thru the hole in the metal cover, then a nut to apply pressure and you have your cover secure.

Of course, this is just a basic idea, this "T" can be made hinged and already attached to the cover to make it easier to use.

This "T" can even have hinged nut in the middle instead of a threaded rod, this way you slide a bolt thru the cover and nothing will stick out from the thank.

Hope someone else can explain this better than me but this is the idea.

I think one can assume that one would need to get into the tank again. For example the pump may fail (will over long enough usage) and need replacement.

So the issue is finding or making a tank pump hole cover. At this point I'm pondering a fiberglass cover molded to the original top portion of the boot to seal the tank. I'm not sure how well the two would bond or how well they would bond using Polyurethane or similar. It would be attached to the tank with a hose clamp like now and thus could be removed to be serviced. BUT I still hope for a better idea.

Nick

[sean]

If there's no need to remove the cover for the hole where the old fuel pump used to be, one could simply RTV a piece of plastic to it.

I use gasoline to clean up RTV, so im not sure how well its going to seal for ya.

[nkemp]

How about one piece of metal with a gasket for the outside (round) with a hole in the middle. .

If a a center bolt is used, a gasketing washer would be needed to minimize gas leakage and gas fume leakage around the bolt.

To build on this idea... one could use the top of the existing boot as the gasket. Cut it so that the crosscut profile looks like an upside down "U". Now take the metal and put a lip around it like a jar lid (building from Farrar's post) so that it stays centered over the gasket. This is where a little adhesive would help to hold the two pieces together.

If the adhesive works well then the bolt is not needed (and maybe not the lip as well). Simply hose clamp the gasket to the tank lip like it is today.

Another method, which I'm still lukewarm on, is to bolt through the top part of the upside down "U" gasket through the metal disk to secure the two. This would still need sealant between the gasket and the metal plate. And the screws might pull through the rubber boot material... A metal ring inside the upside down "U" would minimize tear-through.

The more I think about this the more options...

Cut the existing boot so that it looks like an upside down "J" with the longer leg inside the tank. Use angle brackets with one leg against the gasket and the other the top. Use sealant between the metal top and the top of the "J" gasket. To prevent gasket pull-through a flat metal band could encircle the boot where the screws/rivets go through. The top could be spot welded or bolted (use sealant) to the brackets

BTW ... if metal is used for the seal/cover, the pump's electrical ground connection could use the metal (in other words, no electrical isolation from the metal seal. Then only one wire would need to pass through the tank wall. But... when removing the tank cover, the electrical connection may hinder its removal).

NK

Reminder: I'm "subject to being wrong without notice."

[LEVY]

.

Yes, I forgot to mention that, something like a plastic washer, like in this order: bolt - metal washer - plastic washer (gasket)- fuel tank.

With this setup, no additional sealing material is needed, for easy of service.

Maybe we could use a specially made plug like the one used to plug manufacture holes in engines, AKA FREEZE PLUGS, something like this:

If something like that is used, then just make sure to use a fuel resistant material.

If a a center bolt is used, a gasketing washer would be needed to minimize gas leakage and gas fume leakage around the bolt.

To build on this idea... one could use the top of the existing boot as the gasket. Cut it so that the crosscut profile looks like an upside down "U". Now take the metal and put a lip around it like a jar lid (building from Farrar's post) so that it stays centered over the gasket. This is where a little adhesive would help to hold the two pieces together.

If the adhesive works well then the bolt is not needed (and maybe not the lip as well). Simply hose clamp the gasket to the tank lip like it is today.

Another method, which I'm still lukewarm on, is to bolt through the top part of the upside down "U" gasket through the metal disk to secure the two. This would still need sealant between the gasket and the metal plate. And the screws might pull through the rubber boot material... A metal ring inside the upside down "U" would minimize tear-through.

The more I think about this the more options...

Cut the existing boot so that it looks like an upside down "J" with the longer leg inside the tank. Use angle brackets with one leg against the gasket and the other the top. Use sealant between the metal top and the top of the "J" gasket. To prevent gasket pull-through a flat metal band could encircle the boot where the screws/rivets go through. The top could be spot welded or bolted (use sealant) to the brackets

BTW ... if metal is used for the seal/cover, the pump's electrical ground connection could use the metal (in other words, no electrical isolation from the metal seal. Then only one wire would need to pass through the tank wall. But... when removing the tank cover, the electrical connection may hinder its removal).

NK

Reminder: I'm "subject to being wrong without notice."

[nkemp]

I measured the opening ID: fuel pump hole in the gas tank = 100mm/3.94"

As such we need a 4" bung.

BUT (pun intended) ... This would press up against the metal bracket holding the pump (the metal bracket we use today). So you have rubber pushing agaist the metal that pushes against the tank plastic. It will leak between the metal and tank plastic without another gasket.

Thus I think mounting to the outside would work better.

[nkemp]

After talking this through and some other ideas on the web, I drew up the diagram attached (used Paint.net. Free & easy to use...Visit CNET for DnLd) ... Image not to scale

The BLUE ring may not be needed if the plate retaining bolts could tap into the tank. The trouble is relative to sealing off the bolts so there is no gas leakage. Could use RivNuts :-( or epoxy, RTV the barbless version of the 2nd image ... blind nut. Size bolts so that they do not go through the epoxy/RTV.

Thoughts?

Is there any reason to believe that the pump could not be fully submerged in the tank?

Nick

[sean]

Rather than plumb through the tank itself why not run the plumbing through your metal/plastic plate at the top? You could weld the fittings in place and not deal with hoping epoxy or RTV will seal it to the plastic tank.

[Bitsyncmaster]

Most RTV and epoxy does not stand up well staying wet in gasoline and alcohol.

The fuel pump has not problems being submerged in gas. It will keep it running cooler.

[robvanderveer]

I saw your diagram, personally I don't like 12v hot wire running through my fuel tank. Other than that i like these suggestions.