Turbo II fuel pump rewire
First off I would like to say a few things, get yourself a real Mazda service manual. I managed to do mine with just a Hayne's but it was a pain in the ass. Some of the wire colors did not match and I had to constantly check between Dale Clarks write up (see below), My Haynes manual, answers to my questions on the FC3S mailing list, and my voltmeter readings. Also if you look at the diagram in the haynes the order the wires leave the relay do NOT match the order of the wires at the 6 wire connection!!!. **note: Non turbos are different becuase they don't have the resistor relay that changes the
voltage, which makes things much, much easier!**
Why rewire the fuel pump?
- Even on a car with a new alternator, new battery, new battery
terminals, and clean electrical connections (mine) I saw as low as 10v to the fuel
pump with a load on the system (lights on, stereo cranked, heater on, etc.)
- The fuel pump should, under boost, be seeing at LEAST 12v.
Reduction in voltage=reduction in fuel flow=bye-bye motor.
Considerations when rewiring the pump...
- First off, it should operate as normal. You turn on the key and go; no extra switches, etc.
- The fuel pump resistor circuit should continue to work. This drops
the fuel pump voltage to 9v at idle and cruise to improve fuel economy.
- The safety switch in the air flow meter should continue to work.
The airflow meter, when closed, turns off the fuel pump. So, if you roll the
car, you won't be pumping gas out of the car at 30-40psi making a big fireball  .
Some caveats about doing this job -
1. This is NOT EASY. If you are comfortable with 12v electronics (you've wired up a few
stereos) you should be able to do this. You need to test everything as you go along. If
this doesn't work, your car will not run. If you really hose it up, you could have inadequate
fuel pump voltage. I WILL NOT TAKE ANY RESPONSIBILITY - you broke it, you bought it.
2. I'm also assuming that you know all the standard procedures for wiring stuff - solder your
connections, heat shrink tube or electrical tape all bare wire, etc.
3. Just take your time with it. It's really not that hard, but there's a lot you have to keep
in mind. It took me the better part of an afternoon to do, most of which was double-checking
and triple-checking my theory on how stuff is going to be hooked up.
OK, so how do you do it?
You'll need -
- a 12v automotive relay (Radio Shack - "30 Amp Auto Relay", cat #275-226)
- about 15 feet of 12 gauge wire
- an inline fuse for the 12 gauge wire
- about 20 feet of speaker wire (you need two wire runs to the back
of the car, and speaker wire has 2 wires)
- various crimp-on connectors (to connect to the relay and positive
battery terminal)
- electrical tape
I used about 23 feet of speaker wire running it up the passenger fender, across the fire
wall, and up the driver side door way. I probably used more then 15 feet of power too.
Never hurts to buy more.
I used 10 gauge power wire and 12 gauge speaker.
You will also want a soldering iron. I soldered all my connections.
OK, first off let's run the wire. The speaker wire needs to start at
the airbox location in the engine bay and end by the driver's side rear shock
tower. The 12 gauge wire needs to come from the postive battery terminal to the
same spot (don't hook it up yet! Hook the inline fuse between the positive
terminal and the 12 gauge wire - you always want the fuse close to the
battery. I used a 15 amp fuse, and it seems to be adequate. You might want to run both wires
at the same time - makes it a little easier.
Next, it's time to move the resistor and relay. Remove the airbox.
There's a metal bracket that has a relay and a aluminium box that looks like a
heat sink. It connects to the wiring harness with a large rectangle white
connector.
 
Don't worry, you only want one of these
connections 
Let's label these wires, as per the shop manual. Diagram below is
on the relay/resistor side:
____--____
| E C A |
| F D B |
-----------
On my 89 turboII (canadian if thats makes a diff) A,C,E were all blue w/ red strips
B and F was blue w/ green, D was green w/red
OK, cut the connector off the wiring harness. Leave enough slack on
both sides of the cut - we'll be re-splicing the connections in. Connect the
speaker wire to C and D (one wire to C, the other to D).
 
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