WARNING(virus check bypassed): re. fuel pump wiring question

[Ben Swann]

Randy,

This is based on memory and what I’ve seen in most and what I’ve done.  Yours maybe
different so if this does not jibe let us know.   I don’t have the Bentley for your car,
but should be the same.  There is a set of wires in a black sheath – going to the fuel
pump and usually located under the seat.  The wires are usually brown and Green/Yellow.
The Brown is ground and the Green/Yellow is the positive.  The model 80 may be a little
different and best to ref. the Bentley diagram to be sure.

Now these wires are triggered via ignition and fuel pump relay and carry full load
through the fuse box and other devices.  You should install a relay and use these wires
only to trigger the relay which acts as a switch to carry full current using larger
wires.  The G/Y goes to relay 85 and brown to 86.  The load to the pump will return off
terminal 87 and  +12V power supply to terminal 30 on the relay.  In short - 

Standard Relay wiring terminals are:
85 = switching positive
86 = Ground return for switch
87 = switched positive to load that carries current to device
30 = 12 volt+ supply direct from battery

85 and 86 are used to turn the relay on and close the contacts to make the circuit from
30 to 87.  It only takes a small current to turn the relay on and allow the much larger
current to flow through the relay to the pump.  Fuse should be on the line into 30 and a
good idea to have another located near the battery feed if running an extra feed wire.
Run at least a #8 wire for power.  I usually do a #6 or bigger - massive overkill, but
lets you have capacity for power amp, etc.

Return from pump can go direct to chassis ground, and is probably already wired that
way.  Often there is a hot (+ 12V wire) under the seat of sufficient capacity – if not
run one.  Then the job of relaying becomes easier , and relay can be located there.
Best to put the relay as close to the device as possible, but if not then make sure wire
is more than sufficient to carry the load and have appropriate fusing.

Now for the Type 44(5000 and 200) and Ur Quattro where the battery is under the seat,
wiring is fairly easy since both battery and connector for the fuel pump are located
there and is easy to tap into.  If you are installing the relay in/near the fuse box,
you may want to provide some larger wires to feed the pump and take power from the
battery positive.

You are doing the right thing by relaying the fuel pump.  Next you should do the
headlights!

Ben

[Date: Fri, 5 Oct 2007 20:23:16 EDT
From: McCohens at aol.com
Subject: fuel pump wiring question
To: quattro at audifans.com
Message-ID: <d3c.1458be59.34382f74 at aol.com>
Content-Type: text/plain; charset="US-ASCII"

Putting an 034 IB in my 80 TQ, current issue is wiring the pump.  The  034 
uses ground to switch.  I would like to use the stock wiring and  relay.  Found 
a wire in the old ignition computer harness that turns the  pump on with +12.  
I was planning to hook that wire to a switched +12 fuse  panel just 
installed.  Now I need to find which ground wire goes to the  stock pump relay and hook 
it to the 034 harness.  Can anyone lend more info  than the bentley book?  It 
says a brown wire with a green stripe at  connector T5.  I could really use a 
little more guidance before I start  cutting wires at the fuse box.
 
TIA
Randy]