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Fuel pump

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Old 06-21-2009, 08:28 PM   #1
Join Date: Oct 2007
Posts: 16
Default Fuel pump

I just put in a new wulbro 255 lph fuel pump in but when I bypass the pump on the rail I don't get any fuel. But when I have both hooked up I do have fuel. The pump in the tank is just hanging there not on a braket or anything, could that cause a problem? Please give me some helpful tips.

Tank You
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Old 06-22-2009, 11:44 AM   #2
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Vehicle: 2004 STi, 1965 Mustang GT
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I don't know if this would cause your problem but did you remember to ground the resistance wire? Here's a link to a thread that will help you if you haven't.


'65 Mustang GT-stroker 347 w/Toploader 4-speed
'84 SVO-2.3T at 17 psi
'04 WRB STi
"Dead is dead, it's pretty clear cut"
"Yeah, until we show up with drugs and jumper cables and argue about it!"
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Old 07-14-2009, 12:38 AM   #3
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Join Date: Mar 2006
Posts: 691

An 85-97 Mustang 190 lph fuel pump can be used in the tank of an 84 SVO and
then you can remove the external pump. That is much cheaper than replacing
both pumps. Your fuel guage is not affected.
You can get a pump and bracket from Ford if you like, or you can get the
Walbro pump from http://www.autoperformanceengineering.com/ (part # FPF001)
and get a bracket from a salvage yard from any late 80s or early 90s
Mustang. Then you'll need to replace your fuel filter with a Ranger filter
because it has longer inlet and outlet pipes. Just connect the fuel line
from the tank to the Ranger filter and remove the external pump and the
short fuel line that is between them. Tie up the wire harness from the
external pump so it doesn't hang.

Next you need to replace the resistance wire that is inline with the fuel
pump ground wire with a good wire. Look under the carpet in the hatch. The
wire harness that comes up through the floor is the pump and level sensor
harness. The pump ground wire is the one that changes size from a thick wire
to a thin one. Cut the wire where it is thick, on the pump side of the thin
wire, and solder another thick wire (like 16 guage, no thinner than 18
guage) onto it. Connect the other end of the new wire to a good chassis
ground. I connected mine to the green-painted ground screws near the tail
lights. You'll have to remove the rear interior panel to find them.

If you're in a rush you can install the pump and do the wiring later. But
you'll want to get to it soon or you may run lean at high rpm and boost.
Anthony, I looked up the resistance wire in my 1984 Ford car shop manual. In
volume D, page 24-35-6 shows a wiring diagram of the fuel pumps. It clearly
shows a "Resistant Wire" from the in-tank pump ground to chassis ground.
There are no other resistors shown in the wiring diagram. On page 24-35-2 it
says "The low pressure (in-tank) electric fuel pump is to provide
pressurized fuel to the inlet of the high pressure pump...The low pressure
pump has an external resistor in the electrical circuit to reduce the
operating voltage to 11 volts." That is all I found about it.

From that statement I gather that the low-pressure pump contains an 11 volt
motor. However, the modern in-tank pumps have 12 volt motors so we need to
short across that resistance wire.
84 SVO, LA3, 3rd Gen Bob's Log, Ported Big Valve Head, Ranger Roller Cam, Ported Lower, Gutted Upper Intakes, Stinger Oil Lines, Stinger 3 inch Exhaust.
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Old 07-14-2009, 12:38 AM
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1965, 84, diagram, filter, forums, fuel, gt, low, mustang, pressure, pump, replace, svo, testing, wiring

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