I'm trying out a different engine harness to hopefully cure some running issues. I have the entire harness hooked up except the last plug located near the distributor. I can't remember where it goes. I'm slow so very detailed description and/or pictures would be great.

Engine is a stock '71

Thanks, Mark

*Edited

If it is the 4 wire plug, it goes to the left rear of the relay board.
Tom

My mistake, It's a 3 wire plug about middle of the way up the harness Shares a branch with a plug that goes into a T on the fuel line in the middle of the engine.
It's a 3 wire plug near the dizzy.

*Edit

The last plug in line should be the#2 injector

What colors are they?

plug in the middle of the pic

I think that's the trigger points wire. It goes behind the dizzy. Look behind the dizzy, under the advanced vacuum port. Actually on the dizzy itself. I added a red arrow.

The 3-wire plug goes to the trigger points in the dizzy.

Got it. Thanks everyone!

Unfortunately, car is still running poorly. - Only running on 2 cylinders

Mark, which cylinder is running? It could be the trigger points . You can easily test that with a test light.

The FI trigger points have 3 wires, middle is ground. When the contacts close, it pulls to ground the circuit, telling the ECU to fire (it alternates back and forth between each side)

I'm pretty sure that Brad said 1&3 were running and when he switched the wires around, 2&4 ran and 1&3 went dead. I have no idea how to do anything in the dizzy but replace the cap. I think I have trigger points and another part for the dizzy that I got in a PP tune up kit.

U can use the cut the trigger point connector from one of your bad harness. Connect it to the trigger points then connect the middle wire to ground. Now use a test light, connect one end to the left and one end to the battery. It that side works, the light will come on and off as you crank the engine. Repeat for the right side.

I side controls 1 and 3 and the other side 2 and 4 As I can remember. If you still need help call me.

If its 1&3 or 2&4 that are dead, check to see that akk three grounds on the FI harness ae connected.

They are.

Bump for more info: 2/4 spark plugs are not firing.

I drove home from Hershey on only 2 running cylinders
The car has new plugs and wires ~1K ago.
Yesterday, we rebuilt the distributer with:
Distributor Cap
Distributor Rotor
Distributor Points
Distributor Condenser
I switched out the engine harness and ecu with another used one.

I pulled all 4 spark plugs but 2 & 4 are still not firing.

Help Please.

What about the trigger point test ? Trigger point is not the same as points.

Right but what do the trigger points have to do with the plugs not sparking?

Do trigger points cause the injectors to shoot gas and the spark plugs to fire? I thought (for no particular reason) that the spinning dizzy rotor causes the spark plugs to spark independent of the ECU.

If I'm wrong about that, than Mark should check plugs 22 and 21 on the FI harness for continuity (meaning he isn't getting spark or fuel to those cylinders).

Yes that is the purpose of that 2 prom wire coming from the trigger points to the ECU.
I had the very same issue and a member here Curtis ( the cabinetmaker) pointed it out and it solves the issue.

It's a simple test, can't hurt to try.

A better understanding