75 twin spark wiring loom

[enzo1891]

hi guys
doing a twin spark conversion and i need to use a wiring loom guide, if any one can help. thanks vince

[njh1964]

Hi Vince,

The excellent and very helpful Craig's Place Web site http://www.users.on.net/~craigf/ has pretty much every Alfa 75 manual you will require, including electrics.

FYI... I've copied and labelled the section on the Twin Spark ECU, which I can email you as a PDF, if that would help.

I haven't actually done it yet, but I reckon using this diagram will make splicing the Twin Spark ECU into the original wiring system a relatively straightforward exercise.

Regards,


Nick

[Colin Byrne]

This page also has some very useful diagrams, unfortunately it's all in French but there's still some good info.

http://alfaimola.free.fr/twinspark/schemas/index.html

Although I havn't finished my conversion yet I have "buzzed" out the entire harness for continuity with a multi meter and labeled all the plugs and connecting wires, so let us know if you have any specific questions.

Splicing the harness into another car should be very simple as the TwinSpark engine harness is totally self containted except for
Power In
Ignition In
Fuel Pump Out
AirCon In 1 (signal to the motronic indicating extra load for idle)
AirCon In 2 (signal to the motronic indicating extra load for idle)
Main Power
Main Ground

[Alan Hopla]

Vince,

If all you are asking is how to wire up the original TwinSpark engine loom then this is very easy, I have recently done this in an Alfetta GTV.
As Colin says there is the Main power feed, and the main earth lines which ground through the engine.
Then there is just one 6 way connector that is located at the rear of the plenum, (with 5 wires).
In the Alfetta I have only needed to connect three of the lines of the TwinSpark loom.
1) Light Green and Black - Ignition power feed from the car, for this I used the Dark Green and Black feed to the Alfetta's original coil.
2) Brown and White - Tacho signal to the car, this I connected to the White tacho signal cable from the Alfetta's original coil. (This feed to the car could also come straight off the coil)
3) Pink and White - Fuel pump power feed to pumps. This was a new feed which was run to the fuel pump.

The other two connections are feeds to the ECU in relation to the air-con, "I think" one is to sense compressor running, the other is to sense that both colling fans are running.
These probably increase the engine idle speed to cater for the extra load and help keep up the alternator output.
As I have no air-con I just didn't even bother with them.

Alan.

[Tristan Atkins]

Hey Alan,

For the tacho, did you use the ECU output (brown/green) or the coil? I used the coil and initially the tacho worked perfectly. Now its stuck at 4000rpm and will only read between 4-6000rpm.

cheers,

Tristan

[Alan Hopla]

Tristan,

Not quite sure what you mean here.

I don't think the ECU itself has an output that can feed the tacho, and I don't know of a Brown and Green wire !

In my loom (which seems to match the circuit diagram), there is a single Brown and White (MB) wire that connects to one of the coils.
Both the coils have a lead that this can plug in to, but only one has anything plugged in.
This lead runs in the ECU-engine loom straight to the 6-way connector, (pin 2).
This I have used to run the tacho, using the existing White (B) lead in the car. All works fine.

The two wires in the 6-way connector that I am not using are Grey and Yellow (HG), and Yellow and Green (GV)

Alan.

[Tristan Atkins]

Hi Alan,

sorry, that was supposed to be the brown and white wire.

Tristan