Embarking on a classic car modification project, I recently acquired a 1977 Toyota Celica GT with the exciting ambition of performing a 5MGE engine swap. Sourcing the engine from a 1984 Celica Supra, I knew this would be an engaging project, but as my first foray into EFI swaps, I’ve quickly encountered the inevitable wiring complexities.
The initial hurdle arose when I discovered the engine harness I obtained was incomplete, missing crucial connectors for the Mass Air Flow (MAF) sensor, Oxygen (O2) sensors, and the essential large connector for the Engine Control Unit (ECU). Compounding this, an igniter was also absent from the parts acquired. Seeking a solution, I then retrieved a harness from a 1986 Cressida, hoping for compatibility. However, I soon realized that Toyota’s wiring configurations vary not just across years, but also between models like the Supra and Cressida.
While the Cressida harness appears to have all the necessary components, it’s not a straightforward plug-and-play solution for the 77 Celica with the 5MGE. I’m currently uncertain if the Cressida harness includes the igniter plug, as the igniter itself had already been removed from the donor Cressida, leaving me to determine if this plug is part of the engine or body harness.
To navigate this intricate wiring puzzle, I’ve ordered Toyota wiring diagram manuals from eBay for both the 1984 Supra and the 1986 Cressida. My primary objective is to decipher the pinouts for both ECUs, with the hope that these manuals will provide the detailed schematics required. Adding another layer to the project, the 77 Celica came with an MSD 6AL ignition box, which I’m considering incorporating. However, understanding how to integrate this with the 5MGE harness is another challenge I’m currently researching.
This 77 Toyota Celica engine swap is proving to be a deep dive into automotive wiring, and I anticipate seeking further insights and advice as the project progresses.
