A Hi-Output Fuel Pump For Bigger Engines and Fixing Your Fuel Gauge Sending
Unit by Ray Paulk
Most of us with Fieros would like to get a bit more edge out
of our Fiero as far as ponies are concerned. There are some things we can do to
the stock engine to improve its efficiency like installing a super ignition
system or freeing up the exhaust, but, when it comes to making some more serious
horsepower, turbos, superchargers or larger engines are in order. A problem with
any of these improvements is the need for more fuel. You've got to feed those
beasts to get them to work. You can't make the HP if you are starving the
engine.
If you install a carburated V8, the stock V6 fuel pump may
suffice. The reason is that the stock fuel injected 2.8 demands fuel pressures
in the 40 to 50 psi range. Carburated engines only need about 5 psi of fuel
pressure. By reducing the pressure on the stock pump, the volumetric output
increases. But what do you do if you swap for a larger EFI engine or even
install a turbo or supercharger on the stock 2.8. These engines still need the
high pressure and need more gas.
One solution is to change the in-the-tank fuel pump to an
external electric pump available from most speed shops. This requires some major
changes in the fuel delivery system. You must remove the tank pump and install a
pick-up strainer. Then you've got to cut into the fuel line somewhere and
install the new pump. This is a lot of work which may be unnecessary.
I figured that with all the GM car/engine combos, there must
be a fuel pump which is the same physical size as our stock one but has a higher
volumetric delivery. I checked out a "Hygrade" catalog at our local
speed parts shop, Blue Magic Performance in Bellingham, MA. "Hygrade"
is a line of fuel pumps made by Standard Motor Products of Long Island City, NY.
From the catalog, the stock fuel pump for an '88 Fiero with a 2.8 is catalog no.
EFP189. In checking other GM cars of that era, I found that the '89 Firebird
uses the same fuel pump as the Fiero, with the standard 2.8 engine. But, there
is also an Anniversary Edition of the 1989 Firebird which has a 3.8 EFI engine.
The part number for that fuel pump is EFP154. Since I couldn't see any other
changes I thought that the EFP154 might just be the pump I was looking for.
I called the Tech Service for Standard Motor Products. Once
we got through the BS about why I shouldn't mess with anything other than what
is specified for the car (this guy obviously doesn't understand Fiero owners),
the guy did quote me the specs which are as follows:
EFP189
EFP154
GPH Free Flow:
35-40
50-60
Outside Dia (mm):
37
36.6
Length (mm):
130
127.5
Inlet (mm):
20
19
Outlet (mm):
8
8
Since they looked pretty close, I though I'd give it a shot
and ordered one. Note that the stock EFP189 goes for about $60, the EFP154 cost
me $72.60 through Blue Magic.
Before dropping the gas tank, I relieved the fuel pressure
by the procedure described in the service manuals. I then loosened the tank
enough so I could get a siphon tube into the breather pipe on the tank and
drained off as much fuel as possible. (I had tried going down the filler tube
but there were too many twists and turns.) When I got the tank emptied and down,
I pulled the pump/sending unit assembly out of the tank. The old and new pumps
are identical in size and shape. Even the strainer fits the new pump which is
good as the catalog does not spec a strainer with the EFP154 pump. Since I
didn't get a new strainer, I ran down to Replacement Auto Parts and picked up a
new one. ($5.41) made by Airtex of Fairfield, IL. Its worth mentioning that this
new strainer has a plastic expander inside the screen to prevent it from
collapsing. This is a much needed improvement.
The old pump
was coupled to the outlet tube with a diaphragm type device. I presume the
purpose is to absorb the pulses of the pump and reduce the noise somewhat. I
elected to use the straight piece of rubber tubing which came with the new pump.
If I had to do it again, I'd keep the diaphragm couple as the new pump is
somewhat noisier inside the car. Other than that, it was simply pop the old out
and put the new in.
Calibrating the Fuel Level Sending Unit:
Since you have the fuel pump/fuel level sending unit out of
the tank, you might as well use this opportunity to calibrate the sending unit.
The fuel level sending is actually a potentiometer with a
"wiper" contact, which is attached to the float, and a resistance coil
which is a wire wrapped around a fiber board. The wiper slides along the edge of
the coil and changes the resistance between the wire which goes to the fuel
gauge and ground. Ideally the resistance should go from 90 ohms at full to
"0" ohms at empty.
As most of us know, the Fiero fuel gauge isn't too good at
reading empty. I know from experience, like about 5 times of running out of gas.
The reason for this is that its very tough to get the resistance down to
"0" ohms. There are adjustment screws on the sending unit, but these
don't work too good on the zero end.
What I wound up doing is cleaning and soldering some of the
end loops on the resistor to short them down to zero. This does get a bit tricky
so unless you're used to soldering electronic instruments you may want to take
this to a TV repair shop or the like. Note that you do have a little latitude on
the solder due to the adjustment screws.
After soldering, I "played" with the adjustment
screws and got the sending unit to 90.5 ohms at full and 1.5 ohms at empty. You
must also make sure that from empty, the ohms immediately start to climb as soon
as the float starts to move.
Completion:
With the new pump and the cal'd sending unit installed in
the tank, I proceeded to curse my way through putting the fuel tank back in the
car. (I wonder how Pontiac used to connect all those hoses at the factory? I
always wind up cutting my hand up pretty good in doing it.) But, alas it was in.
I added some gas and turned the key on. What a beautiful sound, the whir of the
pump pressurizing the system. I lowered the car off the jack stands and gave it
a try. Pretty good! Only detriment is that the sound of the new pump is a bit
more noticeable than the old one. But my 2.8 now runs fine with this pump and
when I get the time, funds and inclination to go for the 3.4 turbo, I'm all set
with the gas supply.
So there is a high output, high pressure in-the-tank fuel
pump for the Fiero. Get the one which is made for the '89 Anniversary Edition
Firebird. It fits like it was designed for the Fiero.
Hope this helps someone.
Ray Paulk
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