Another fuel tank plumbing option

[nkemp]

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

Homebuilt aircraft have been making fiberglass tanks for years. Are we talking about the same "epoxy"

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.

The RV/Epoxy would be for the nuts through the tank to hold the top plate. I want the top plate to be removable for service WHEN the pump fails ... and it will.

The main reason for going through the tank(using purpose designed through tank fittings) is to make it easier to service the tank & pump. Gets them out of the way and no need to disconnect when opening the tank.

Nut see the next post ....

Nick

[Ron]

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.

+1 !

Tangent: Don't tell Bill this but, when I was considering putting a carb on my D, I was thinking about a plate/cap with a single hole/fitting for a fuel line running to a rail mounted pressure regulated pump -- (Wires are outside and no return needed...You set the pumps cutoff pressure slightly above the carb's needle-seat pressure requirements but below the pump's bypass pressure and it will last ~forever.)

[nkemp]

The GM units have intrigued me for some time. I took home the unit from the Astro when it failed. There are a couple variations and look like the photo.

The top has an in, out & vent port. All wires use the top plate.GM pump.jpg

As it turn out, when the gasket (not shown) is used they are near perfect fit. The trouble is that they are spring loaded (Up/DN) and when compressed they do not fit in the tank. When the springs are removed, they should fit.

BUT... the problem is still how to hold the top plate down. Again, something like the ring in the diagram is needed (on standard applications there is a threaded or lock ring retaining the unit).

Servicing this unit is easy since everything is attached to the assembly (including the fuel sender (not D compatible resistance))

They have great sumps that have back-flow valves so that the sump level remains after the pump stops. Corner hesitation should be eliminated with the GM design. Some suck the fuel from the sump, others suck from the tank bottom (preferred for max fuel availability) There may be other Mfr's that would work but I have not seen them up close and personal.

What I do not know about this pump assembly is the pressure & flow curves. What is the flow at D required pressures? Or would we need to strap the D's pump to the outside of the assembly with some replumbing?

Nick

[Ron]

What I do not know about this pump assembly is the pressure & flow curves. What is the flow at D required pressures? Or would we need to strap the D's pump to the outside of the assembly with some replumbing?

Nick

That pump is about 10psi too low.

If you are considering mounting any pump extrernally, see two posts up ;-)

[nkemp]

All the pressure & flow info I could find was after the pressure regulator on GM vehicles. 10PSI low at the pump?

Close but no cigar,

Nick

[Ron]

Yeah they are looking for 66psi in tests (1999 4.2 TBI...they dump the unused back). We have a check value of 71-79.7psi. I'm sure they are capable of more but too close for me... IIRC my D pump was closer to 90psi true pressure.
If you surf around, you can probably find a better one. I can pull the OEM data on one if it looks right but don't give the pressure data for you.

[LEVY]

Most, if not all modern vehicles, have 12V running inside the fuel tank! But.....

The setting have been designed by professionals.

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

[sean]

The GM units have intrigued me for some time.

Nick

FYI, it seems DMCH may be interested in the same thing. Kevin Abato posted these gems to FB:
299049_10150360488267948_806842947_8140785_317279191_n.jpg
307516_10150360487487948_806842947_8140778_1893594947_n.jpg
http://a4.sphotos.ak.fbcdn.net/hphot...93594947_n.jpg
http://a2.sphotos.ak.fbcdn.net/hphot...17279191_n.jpg
It seems they have a pump/sender assembly in the works.

[nkemp]

Great minds think alike. :-)

I'll be interested in seeing how they secure the pump to the hole.

From the photos I can't tell if their pickup is inside the sump or outside (we want the latter).

Also, what pump are they using?

[Bitsyncmaster]

Homebuilt aircraft have been making fiberglass tanks for years. Are we talking about the same "epoxy"
Nick

The experimental aircraft tanks are sealed with a "slosh" sealer. Only epoxy that comes close to gas proof is vinylester. But even then that's with aviation fuel that has no ethanol.