# Pre-OBD to OBDII ABA swap wiring



## itsnot_emkaytwo (Feb 27, 2015)

I bought an ABA engine with complete wiring harness, and I chopped down the harness to the NLS plug-n-play harness -










My golf is a pre-OBD car, and I have everything I need - harness, ECU, relay box, etc. My issue is, where does the fuel pump wire go? The fuel pump obviously won't run if no power is going to it. In my wiring harness, the fuel pump wire only goes between the ECU and the relay box. It doesn't go to the fuel pump, or the connector that runs to the back of the car to the fuel pump. How would this work? As the directions say in this picture, it just says to connect the wire to the relay to power the relay. Aside from that, nothing goes to the relay. Otherwise, the fuel pump would be hooked up to the original pre-OBD relay box, which wouldn't make sense.


----------



## need_a_VR6 (May 19, 1999)

What chassis/fuseblock are you swapping?


----------



## UT87GTI (Jul 9, 2015)

Subd,
I will be following this. BTW thank you for the post and info!!!!

Would this wiring retain the ability to use the OBDII port to diagnose the engine/codes?


----------



## itsnot_emkaytwo (Feb 27, 2015)

need_a_VR6 said:


> What chassis/fuseblock are you swapping?


It's a 1986 golf with us built wiring, the crappy white relay panel with separate fuse panel


----------



## itsnot_emkaytwo (Feb 27, 2015)

UT87GTI said:


> Subd,
> I will be following this. BTW thank you for the post and info!!!!
> 
> Would this wiring retain the ability to use the OBDII port to diagnose the engine/codes?


As far as I've heard, it very well should. The wire will still be connected to the harness so all you'd have to do is grab an obd2 port from the junkyard or something and solder it in.


----------



## need_a_VR6 (May 19, 1999)

Without looking at the Bentley for an 86, I'd suspect because it's CIS it would wire in more like a mk1 where you don't have an ecu based fuel pump trigger.


----------



## itsnot_emkaytwo (Feb 27, 2015)

need_a_VR6 said:


> Without looking at the Bentley for an 86, I'd suspect because it's CIS it would wire in more like a mk1 where you don't have an ecu based fuel pump trigger.


I actually figured that part out recently, the yellow/blue fuel pump trigger wire gets spliced into the stock wire in the mk2 behind the relay panel. As of now, I'm trying to figure out where that 30 amp relay in the picture is wired to, and where the battery + and - and wired to, since they're not in my harness.


----------



## InlinePerformance (Oct 25, 2008)

. I build a nice harness if tou get sick of splicing into mkii fuse box messes  just offering up-good luck!!! Aba is such a good reliable swap!!!! 


Sent from my iPhone using Tapatalk


----------



## bayareafast (Apr 7, 2008)

looking at the diagram provided is that all i need to plug in and make this puppy move? Is there any other sensors/components i need to plug in or have? is this the bare minimum needed with an obd2 ecu?


----------



## vanagonnut (Jul 14, 2016)

re fuel pump. Don't know if this info you're looking for but....

you could always run a new + wire from battery or starter post to 30 of FP relay, then 87 of that relay out to pump. As per your comments, under OBD2, looking at Bently A3 diagrams, 15 buss key power connects to one leg of FP relay (e.g. 86) and once engine is running ECU provides a - path to FP relay to turn it on so pump will run. IOW that relay is switched on the ground side. As per diagram, you could use that new + wire to also power the heater element in each O2 sensor. If you're running those. + power from 87 of FP relay is fused to FP + and each O2 sensor heater element.

Edited. wrote: HO2S. Meant: O2 sensors


----------



## bayareafast (Apr 7, 2008)

vanagonnut said:


> re fuel pump. Don't know if this info you're looking for but....
> 
> you could always run a new + wire from battery or starter post to 30 of FP relay, then 87 of that relay out to pump. As per your comments, under OBD2, looking at Bently A3 diagrams, 15 buss key power connects to one leg of FP relay (e.g. 86) and once engine is running ECU provides a - path to FP relay to turn it on so pump will run. IOW that relay is switched on the ground side. As per diagram, you could use that new + wire to also power the heater element in each O2 sensor. If you're running those. + power from 87 of FP relay is fused to FP + and each O2 sensor heater element.
> 
> Edited. wrote: HO2S. Meant: O2 sensors


all good to know and worth jotting down. What i was looking for in terms of an answer is as long as all those components are hooked up i should be fine and the motor wont freak out and run poorly? Im want to eliminate as much from the donor as possible and be left with the absolute minimum needed to have this running smoothly. No co2, no airpump, no charcoal canister what else can be taken away?


----------



## syncrogti (Sep 5, 2005)

Resurrecting an old thread, I am doing this wiring harness work now. Is the relay shown in the NLS diagram for the fuel pump?

Plan to go to Microsquirt once this is up and running, in order to go turbo (instead of a chip tune)


----------



## itsnot_emkaytwo (Feb 27, 2015)

syncrogti said:


> Resurrecting an old thread, I am doing this wiring harness work now. Is the relay shown in the NLS diagram for the fuel pump?
> 
> Plan to go to Microsquirt once this is up and running, in order to go turbo (instead of a chip tune)


Damn I forgot I made this thread haha but yes, that is for the fuel pump


Sent from my iPhone using Tapatalk


----------

