320 LPH Fuel Pump and Sender Installation - Fox Body
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Whether you've increased your Mustangs fuel
requirements or need to replace a dying fuel
pump or sender, the installation of a new part is
relatively straight forward.  In the following photos
I've replaced a 255 LPH fuel pump with a 320
LPH fuel pump in a non-stock application.  In a
regular fuel pump installation, you would need
special tools to release the stock line fittings.  

As your first step, I would recommend driving or
draining the tank to around 1/4" full and
disconnecting the negative side of the battery.  
Fuel weighs approximately 6lb per gallon.  Even
having 25-30 lbs of fuel rolling around can make
for a challenging time if you're using a basic
vehicle jack.  One suggestion would be to make a
simple platform for the jack to increase the
surface area under the tank.  A lift will certainly
make the task easier but no less dangerous.  A
second set of hands during the removal would
add stability to the tank.  

Items you'll need to remove before you can
completely free the tank are the main electrical
harness, vent line, feed line, and return line.  
Remove the bolts holding the gas filler to the
body to allow the filler tube to move more freely.  
There is also one bolt holding a filler tube
locating bracket at the tank.  Depending on your
application and what may have been done in the
past will determine how much space you have to
work with to free the lines.

I would suggest using a brass punch and mallet
to avoid creating any sparks at this location to
remove the metal rings.
If you're working on the ground, this tip will help you get the tank out from
under the vehicle...

As the two strap bolts are removed the straps will hang to the rear.  This
makes it difficult to pull the tank straight out the back of the car.  On the
bumper side mounting point, the straps are held in place with a metal pin
through a loop in the strap.  Looking at the mounting box sides, you'll see
the passenger side has a larger hole.  If you take a small magnetic tool,
you can easily catch the pin and pull it straight out the hole.  This will
allow you to free the strap completely.  Just push the pin in the strap loop
for the installation.
The fuel gauge sender replacement is very straight forward.  Remove the retaining ring with your brass punch and pull
out the sender making sure to capture the rubber seal.  There are locating tabs on the tank surface and the underside of
the sender base to ensure you install it correctly.  Use a new rubber o-ring seal on the installation.  There are two things
to watch for on the installation.  One is that the seal stays in its lip after you fit the sender in place.  The second is the
mounting of the retaining ring.  The retaining ring catches three metal lips on the tank surface.  There could be enough
play in how the ring sits inside the three tabs where one tab may not catch securely.  Be sure each of the three tabs is
secured and that the area of retention is spread out equally.
The older 255 LPH pump was being replaced due to an increase in odd
fuel pressure behaviors and I wanted to change to the -8 feed and -6
return fittings.  I had been using the -6 compression fitting on the old
pump but I couldn't get the compression fittings to work right on the
small return line.  The new pump and connectors allowed me to change
the system to a more reliable installation at the tank.  The new 320LPH
fuel pump bracket also uses the larger 3/8" metal feed line from the
94-95 Mustangs.

Installation on the pump is similar to the sending unit.  Use a new o-ring
seal during the installation and pay particular care to align the pump
filter correctly.  The long end of the filter will face toward the front of the
car.  If you look at the picture to the left, you'll see the filter, the lines,
and the electrical connection are not in line.  Depending on what you
purchase the filter may or may not come installed.

As you wiggle the pump in place, you need to make sure the pump fits
correctly inside the tank baffle.  Look inside through the filler seal after
it's installed to check.
I purchased the pump and bracket as a complete
unit from High Flow Performance.

www.highflowfuel.com

The first pump that was sent out ended up having
the tiniest of holes in the tig weld on the return
fitting.  Literally an additional half second on the
weld was all that would be needed to solve the
problem, and I needed glasses just to see it.  After
contacting the company, they apologized and sent
out a new unit without hesitation.  I had a new
pump and bracket across the country and at the
door step within 48 hours.  I want to give them
props for their excellent customer service.