To start, shortly after my lsx swap, my factory fuel lines sprung a leak right next to the drivers side header. Rather than just half assing it, I figured I would add a sump and external pump because I am planning on just over 400 RWHP with my mildish 6.0, and I doubt the OE tpi pump will keep up. I am going to have my buddy weld 2 -8an fitting on the bottom rear of the tank (one feed one return far enough apart) facing straight down with 90* fittings turned forward to run the braided lines over the axle, where I plan to mount my walbro 255lph pump in FRONT of the axle. Yes, the external pump will be mounted level with the lowest part of the fuel tank, but the pump will be about 2-3 feet in front of the -8an bung fitting. Does anyone see any issues with fuel starvation on hard acceleration with this setup? Thanks in advance, I hope this is in the right section...

 

Why go so crazy? Just put a walbro in tank 255 in and be done with it. Your plan is overkill for the power goals you have.

 

I already had this external walbro for another axed project on the shelf. Later down the road I might introduce some giggly gas or a turbo... do it once do it right... Also I dont want to cut up my car with the hatch/trap door mod, and dropping the tank to change fuel pumps is a PITA. Hence the external pump/sump

 

Your plan is overly complicating a simple system to which you'll likely have fuel slosh problems around the feed. If you want to do it once you should put in a aeromotive 340 or Walbro 450 with a hot wire feed. Dropping the tank can be a pain but is the cleanest means to your end. Either of those afore mentioned pumps can support 700+ hp. Or, install the Detroit speed trap door kit so you only have the pain once. Welding on a stock tank is not a good idea.

 

I'll think about it for the weekend, and let you know which direction I go and post pictures. I am leaning towards the bungs in the bottom of the tank, as I can always turn my second bung on the bottom into a second feed with a y at the pump, and then route my return up top through the factory sender. But that would be only if needed. Thank you for the advice, I'll think hard about this one

 

You're not actually thinking of welding on the stock tank while it is in the car are you? Even if you did get a fitting on the tank it wouldn't feed/drain properly. You will suck in air as the fuel sloshes around and have uneven flow from an aftermarket pump running through a -8 fighting with the stock TPI pump. Just drop the tank, and do it correctly. You'll spend less time in the end and have a car that didn't burn your house down.

 

The tank is already out, and thoroughly cleaned, prepped to weld. How will a -8an bung suck air from the bottom rear of the tank? It will always be covered in fuel. The stock TPI pump will remain in the tank, but will not be used. Its only in there for my fuel level sender. In no way will the TPI pump be utilized. There will be two 8an fittings welded to the bottom of the tank, one for feed and one for return, and if need be I can turn both 8an fittings into feed lines with a y fitting to my external walbro, and then route the return up top using the OE return tube. Back to the original question, will there be a fuel starvation issue with the pump being mounted in front of the tank, but level with the 8an fitting on the bottom? There is nowhere to mount the pump behind the tank as my exhuast is in the way.

 

Fill a plastic tub with water and poke a hole in it. Now slosh it around and watch the stream. The momentum of the fuel slosh will counter gravity that is trying to send it south. Meaning, uneven flow. As soon as the tank is low enough you will slosh the fuel to one side exposing the fitting. Your idea will bypass the means to counter this, namely a fuel sock and baffeling around the pickup. If the tank is out of your car, it still has to go back in? So I am lost why utilizing a new pump in place of the TPI pump is not easier? I am not trying to be difficult, but your idea is bypassing the needed functionality that an EFI tank requires. I don't see any benefit of your proposed idea other than to reuse a pump you had laying around.

 

Sorry if I came off snarky on that last reply. You hit the nail on the head this time. I want to use this pump I already have laying around. As for the fuel slosh, I can see how that could be a issue. I did not fully consider that aspect. Thank you for the reply!

 

Absolutely no worries, I'm just trying to help you avoid a lot of hassles without stifling your creativity. Trust me when I say we've all been there. You might be able to sell that pump to offset the cost of an intank unit.