Poly tank from Vintage Tank Solutions install discussion.

[Derek]

I purchased one of their new poly tanks for my 240 that are designed to accept an in tank pump. I thought before I hacked into it I would start a thread to kick around some ideas.

 

Here is my list of areas I want to address:

 

In tank pump. I already have that figured out. I purchased a Tanks Inc. Fuel Pump Assembly Plates GPA-A which will accept my current Walbro pump that resides in my current swirl pot.

 

I haven’t settled in yet on what exact pickup arrangement I want to use and would welcome any suggestions. I’m not auto crossing just spirited public street driving. The stock Walbro pickup may be fine.

 

Venting to handle fuel consumption and fumes. I found a previous thread

https://forums.hybridz.org/topic/133662-homemade-gas-tank-venting-design-considerations/

where AydinZ71 mentions using a double check valve arrangement from Mcmaster Carr that allows fumes to escape but still allows air in. I plan on using this method.

 

Fuel level sender that will play nicely with my Speed Hut fuel gauge. This is one of the main reasons I’m switching to this tank. The stock sender just sucks with their gauge. They sell a universal lever style

https://speedhut.com/accessories/sensors/fuel-level-sensors/240-33-ohm-resistive-float-fuel-level-sensor/

but I’m not crazy about staying with a lever type sender. There are a variety of 240-33 ohm straight tube senders available. Tanks Inc. sells one just not sure about the quality. Again I would welcome any feedback on this.

 

Venting for filling. This is an area that has vexed me for quite a while. My problem is if I fill the tank in the morning when it’s cool out and drive right to the shop as the Florida day heats up there is enough expansion in the tank that it pushes raw fuel all the way through my expansion tank and it starts dripping out of my open air vent line. The first time it happened I pulled the gas cap and raw fuel came gushing out.  I’m pretty much convinced that there is air trapped in the left side of the tank when filling and in fact on my 73 there is a 5/8 diameter ish nipple on the left side of the tank that I had blocked off years ago. It’s there for a reason and I think that’s the reason. Not sure how to solve that with the poly tank since there is no provision for a tube and there is no way to get a bulkhead fitting in there.  The second vent is at the top of the tank and feeds into the fill neck to allow air to escape while filling. I Imagine it should be pretty easy to install a bulkhead fitting and hose when I cut the tank to install the pump.

 

Drain plug.

If I’m switching to an in tank pump I really would like to have the ability to drain the tank easily. Here again I’m thinking bulkhead fitting.

 

That's about all I have at the moment.

Derek

 

[Nigel]

I'm using one of these for a vent valve:

 

https://fuelsafe.com/tpv6-in-line-pressure-relief-vent-valve/

 

It's a two way valve that in addition to allowing air to vent in, it also allows excess pressure to vent out (hot day with hot fuel), but without allowing fuel to leak out in the event of a roll-over.

 

Nigel

[Derek]

Not much action here but figured I'd throw it out there.

 

Vintage Tank Solutions vent question

For those who are running one of the tanks how did you handle the vent for the fuel neck. Blocking that off means that the tank has to vent through the incoming gas and can be problematic. Just curious what others have done.

Thanks,

Derek

[Dat73z]

@Derek I'm planning to run 2 vents. The fuel filler vent to the evap tank near the rear shock tower, which then goes to a one way valve and vents back into the rear fenderwell (I'll likely plumb in a charcoal canister for fumes). The second vent is on top of the tank on the fuel pump plate, also feeding back into the evap tank. 

 

Are you still having fuel tank backpressure issues? 

[Derek]

19 hours ago, Dat73z said:

Are you still having fuel tank backpressure issues? 

On the stock tank? Yes. I haven't started the poly tank install yet. I'm convinced Nissan added the vent on the left side of the tank to deal with the situation. There is no other reason for it to be there. You have to be in just the right climate and usage for it to be a problem. Cool morning fill up, and then parked in the sun all day. There is a real potential to form a vapor bubble there and it expands at a greater rate than liquid. Since I have that plugged the vapors path to release is to force all of the gas that is in the upper section of the tank out if it can. A proper check valve system in the vent line to atmosphere would probably solve it but I'm not crazy about having a pressurized tank.

 

I've just finished testing some polyurethane tubing submerged in gasoline for a few weeks with no sign of degradation. I have a plan to use that as an in-tank vent line. I'll post pictures when I finish it. I also ordered a Tanks Inc. 6" backing ring and I'm going to machine my own custom top plate to provide the inlets and outlets I want.

Edited December 9 by Derek

[Dat73z]

Look forward to your updates @Derek. I'm hoping to get to my VTS install early next year once I get some adapters machined for my in-tank surge tank. 

 

I agree all of the vents on the later 240z tanks makes a difference. I recall when I was deleting vents many years ago on my 1973, I ran into issues where I actually could not pump more than 1/2-2/3rds of a tank due to trapped air which was a major nuisance. So I went back to all OEM vents and the issue went away.