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How to sump your stock gas tank!

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How to sump your stock gas tank...

Write-up is short and to the point if you have any question that are not answered here feel free to contact me (330CubeGt)

Steel Fuel Tank Sump for 1979-2004 FORD MUSTANG. This sump is specifically designed to fit the curvature of the Mustang's fuel tank.

Two L-shaped cuts need to be made to the sides of the sump near, the rear of the sump, removing about 1" of the sides.

This allows for the sump face to be rolled down to match the curve of the tank.

Then weld the assembly in place.It is designed for aftermarket-style high-flow fuel systems.

Includes two welded-in 1/2" fittings, template and installation instructions. Dimensions: 7-1/4" wide X 10-3/4" long X 3" deep.

NOTE: Welding and cutting is required for installation. You will also need an external fuel pump and lines.

Due to the potentially dangerous nature of welding a fuel tank, please read and fully understand the instructions before installation.

Made of 18 Gauge steel!

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I purchased my Sump from Mustangs Unlimited .Along with the sump i ordered the required AN fittings from Summit Racing.Fittings May Vary depending on Fuel System setup etc.

In my case i ordered a 1/2 NPT plug along with a 1/2 NPT to -8 Male with a -8 Female to Hose 45 Deg.

Before you do anything Drop the tank out of the car, Drain what gas is left out of the tank.Wash it out with some Dawn Dish Soap and water and make sure its at clean as can be and there is no gas anywhere in the tank.Then Dry the tank inside and out.

This is what it looks like when it arrived.


Once you have the tank Dry.Sit the Sump on the bottom side of the tank and get it centered up and where you want it.I centered it up measuring off the Indentions for the straps.Once you have it where you want take a Marker and Trace out the Sump on the tank using a permanent marker.


This next step is not important if you are doing this to a 94-97 Style tank.

The 98-04 Tanks have the Fuel pump Basket on the bottom of the tank.The Piece the basket snaps into is plastic but molded to a metal ring that is spot welded on the bottom of the tank.

In this picture you will see i marked where the spot welds were along with where the basket sits in the tank.


After Marking the basket location your ready to punch some holes in the tank.With out the worrie of hitting anything,In my case i used a 3" hole saw putting a (1) hole at the very bottom of the tank next to the stock basket.along with (1) hole at the back of the tank.


After you punch the holes in the tank you want to clean the surface edge of the sump along with the tank in my case i used a 4.5" angle gringer,Once you have the Surface area cleaned put the sump back into position.


After you get it where you want it your ready to tach it in place.In my case i used a craftsman 90 amp mig welder with a lincoln flux core wire.030.Not the prettiest of welds but it gets the job done.


After you get it tached in place you can go ahead and finish welding the sump completly.After your done welding fill the tank with water to check for leaks,If you have leaks repeat the process grind down the existing welds and re weld the pin holes if any.

Your not done yet, Don't forget about the gas tank cover.

Previously i took the sump and did the same steps as i did to the tank to the cover, since the cover is black to make my markings visable i used some blue painters tape to drawl my outline.I then outlined the sump then took away the width of the lip around the sump for a snug fit to the sump its self and it also hides the welds once on the car.With that said this is how it should look.


Once you have it marked where you want to make the final cut your ready to go.In my case i took my 4.5" Grinding disk and replaced it with a 4.5" cut off wheel.After your done cutting it should look like this.


While i was at it i cleaned up the cover and used some light sand paper and hand sanded around the edges where i cut to clean it up along with a few other spot that were rough.Now with it somewhat smooth i then Painted it with gloss black rustoleum spray paint.When your done it should look something like this.


Now your just about done, now all thats is left to do is put the cover back on the tank and get the gas tank back in the car!

And this is the end Result.


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educate me, what is the advantage of a sumped tank. Help with not losing pressure?

It's not pressure loss it helps to keep the fuel pump from starving under high g-forces.

By definition a sump is "a pit or hollow in which liquid collects, in particular." Basically as the tank sloshes, the "pit" or sump will collect fuel to fill it and send it to an externally mounted - inline fuel pump allowing the car to always have a bowl of fuel to send to the rails. That being said the most preferred way to go is a cobra tank as it is internally baffled and channels the fuel directly to the sump in the tank.

Edited by iRoush
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