Couldn't find this covered in any of my searches. Anyway, the car is an 88 gxl, I have a motor from a 90? GTUs, in the process of putting it all together, I'm using the S4 injectors in the S5 fuel rail on the S5 intake manifolds. The problem comes from the S4 BAC valve, there is not enough clearance between its plug and the S5 fuel rail to connect it. I've though about loosening the fuel rail to get the connector on and then forcing the two together but the thought of something rubbing the fuel rail constantly don't sit well with me. I was thinking I would just cut the connector for the S5 BAC valve off the S5 harness and solder it onto the S4 harness to use the S5 valve. Does anyone know if there are any electrical differences between the valves besides the connector locations?
Thank you in advance

 

Just the connector location is different. You can "extend" your harness for the BAC by cutting the tape holding it to the main harness, it should give you a few inches. But since the connector is different, you can always solder the S4 BAC harness to the S5 main harness and extend as you need. Shrink wrap when done.

You may be able to use the S5 harness for the BAC, compare the clip to the s4 clip, if I remember right, you may be able to just file down the middle "tab" on the BAC harness plug.

 

Thank you. I reread my post and wanted to clear up my question, the wire length isn't a problem. The location of the S4 BAC connector is right next to the S5 fuel rail. This is an S5 engine in an S4 car. I might just end up cutting the BAC connector off the S5 harness and soldering it to the S4 harness which should allow me to use the S5 BAC valve. Does anyone know if it is compatible with the S4 ECU?

 

It will work fine. Its the same BAC internally.

If you haven't done it yet, I recommend you keep your s4 hareness original and just modify it (by shaving it) to work with the s5 BAC. This way you will have a nice s5 harness IN TACT that someone in the future can use, and your S4 harness will also be original, so you or the future owner won't have headaches with.

I found a thread that covers this.

https://www.rx7club.com/showthread.p...&highlight=bac

hope this helps. let me know how modifying the s4 plug to fit the s5 BAC works.

 

Thanks again jjcobm, I just used a file to shave down the connector. It might still be touching the fuel rail a little bit but not with as much pressure as it was before.

 

Perfect, now you have two harnesses that are in tact and not hacked away. With these cars becoming old, try to preserve as much (keep it original) as you can since it will come handy down the road.