# Need help with Digi 2 wiring.



## kim_gulle (Mar 19, 2011)

Hi there! 

New on this forum, but have been lurking for a year or so. Mainly i hang around the Swedish GTI forum since i am swedish. People over there does not seem to be able to help me with this problem though and by looking in this forum, a lot of you seem to be working with the Digifant systems. 

Anyway, i have a Mk1 GTI with a MK2 8v 1800 GTI engine swap. Sadly though it seems my K-Jetronic is starting to get worn after the 330000 km of it's life and it gives me a huge fuel consumption. Mind you, i know a lot about these injections and understand how they work. I have 3 more cars with this injection. 2 competition cars and a Mk2 16v. Anyway, i have measured everything that can be measured and everything checks out fine. Spark plugs and oil was changed around 2 months ago. 

Since i'm practically getting ruined by driving the car, being a university student and all, i've been thinking about swapping the CIS injection to a Digifant II i have lying around, sourced from a -89 Passat GT with the PF engine. I guess that since the PF and the EV engine, which sits in my mk1, are practically the same, the Digi II should work fine on the EV as well. 

The problem i have with this Digi 2 though are the 5 wires going into the compartment which i don't know what they're for. I know one of them is RED/WHITE, one is BLACK/YELLOW i think and then there's some more as well. I can take a picture of the connector and the cables if needed. 

Thanks.


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## WaterWheels (Aug 14, 2005)

Only three wires I can think of that "should" run into the driver's compartment, if that is the campartment you mean. One is black/yellow as you said and it is the ECU power which comes from a Digifant control relay. Your car does not have this and you will need to wire one in which is real easy or just use another source for power. I would install the relay as it makes for a stronger power source and Digifant "reads" battery power while in operation. Another wire is a red/yellow which is the ground for the fuel pump. This is grounded through and by the Digifant ECU to keep the fuel pump relay closed. There is a red/green wire that is connected to the starter motor activation curcuit (50) to tell the ECU when the engine is being started. Red/white might be for the injectors, power, and could come from the fuel pump relay or the Digifant control relay. To be honest, I would use a "pin out" diagram to match the wires to the pin location and not go 100% by color. I have made a few harnesses and do not always use the correct colors, maybe someone else does too and that could be an issue, plus the colors fade and get dirty so red/white could look like red/yellow and so on.


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## kim_gulle (Mar 19, 2011)

WaterWheels said:


> Only three wires I can think of that "should" run into the driver's compartment, if that is the campartment you mean. One is black/yellow as you said and it is the ECU power which comes from a Digifant control relay. Your car does not have this and you will need to wire one in which is real easy or just use another source for power. I would install the relay as it makes for a stronger power source and Digifant "reads" battery power while in operation. Another wire is a red/yellow which is the ground for the fuel pump. This is grounded through and by the Digifant ECU to keep the fuel pump relay closed. There is a red/green wire that is connected to the starter motor activation curcuit (50) to tell the ECU when the engine is being started. Red/white might be for the injectors, power, and could come from the fuel pump relay or the Digifant control relay. To be honest, I would use a "pin out" diagram to match the wires to the pin location and not go 100% by color. I have made a few harnesses and do not always use the correct colors, maybe someone else does too and that could be an issue, plus the colors fade and get dirty so red/white could look like red/yellow and so on.


 What you're saying is actually making sense. This is a pic of the connector i'm having trouble with: http://img690.imageshack.us/img690/3376/img1489cy.jpg 
The numbers 1, 14 and 3 are the pin numbers to the ECU according to this: http://www.a2resource.com/electrical/management/digifant2.html 
As you say, those three are the ones that you mention. But what are the other two wires, 4 and 5 for?


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## WaterWheels (Aug 14, 2005)

Picture helped a lot. The connector which you pictured should be labeled "T5" in a wiring diagram. It could be a variation of that due to different models, like "T5a" or "T5b", but will be at a minimum "T5" and should be described as being in the air plenum. I only have a VW wiring book for Golf models and using that the wires are a little different in position but the colors are the same except for the red is red/black. This is how the 91' Gold with Digifant II shows the wires: 
T5/1 = red/white and is power to the O2 sensor heater 
T5/2 = red/yellow and is the grounding wire for the fuel pump relay (through ECU) 
T5/3 = red/green and is the start signal (curcuit 50) 
T5/4 = black/yellow and is power to the ECU pin 14 
T5/5 = red/black and is power to the fuel injectors 

You should be able to use that information and check if the wiring is the same but different in coloring or completely different, position and coloring. I have a Passat manual somewhere but can't seem to find it right now.


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## kim_gulle (Mar 19, 2011)

WaterWheels said:


> Picture helped a lot. The connector which you pictured should be labeled "T5" in a wiring diagram. It could be a variation of that due to different models, like "T5a" or "T5b", but will be at a minimum "T5" and should be described as being in the air plenum. I only have a VW wiring book for Golf models and using that the wires are a little different in position but the colors are the same except for the red is red/black. This is how the 91' Gold with Digifant II shows the wires:
> T5/1 = red/white and is power to the O2 sensor heater
> T5/2 = red/yellow and is the grounding wire for the fuel pump relay (through ECU)
> T5/3 = red/green and is the start signal (curcuit 50)
> ...


 I just figured it out. Seems to be a bit different from your description though. 
This is the correct wiring for my particular connector in the picture: 

1: +12v starter power (50) 
2: +12v ECU relay 
3: O2 sensor heating from the fuel pump relay (87) 
4: Fuel pump relay (87) 
5: +12v to injectors. 

Right now the fuel pump is being powered through a seperate relay that gives the pump constant power when the ignition is on. (I've had trouble with the standard relay) I'm a little unsure about the connection between the ECU and the relay though. According to a guy i've just been in contact with, pin 3 and 4 can both be connected to output 87 on the fuel pump relay and run on the 10 amp fuse that sits on the relay. Does it matter to the ECU if the pump has constant power on ignition and not like with the standard relay which lets the pump run for a few seconds and then turn off while on ignition?


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