One of the great downfalls of the common 4G63 engine swap, is that so many people begin them and never finish. It seems that enthusiasts spend endless money gathering parts and information, they get the engine installed in the vehicle, begin the wiring, and promptly throw in the towel. The vehicle then gets parted out and the engine swapper moves on to something else. I have seen this around 6000 times, probably more, and it hurts my soul.
Rather than get sad about it though, I got inspired to help. See, the common denominator in most of these 4G63 swap part-out’s was the wiring harness. If you have never dug into one before, it can be incredibly overwhelming, especially when you pull the electrical tape off. The once organized DSM harness becomes a spiderweb that has no beginning or end. WTFUXORS ensues.
So, in the interest of helping fellow 4G63 engine swap enthusiasts, I created a couple of wiring schematics. One is a wiring diagram for a 1990 4G63 DSM. The other is the wiring diagram for a 1991-94 4G63 DSM. Each one shows how the wiring harness needs to be setup for an engine swap. Most importantly, it shows the MPI relay, which is the most challenging part to understand.
With that said, hopefully some people will find these diagrams beneficial, and if so, let me know. If not, let me know what I can do to improve them.