Depotting An Ancient Car Computer

Carburettors were king for decades, until the onward march of technology brought electronic fuel injection to the fore. During their final years, a handful of automakers experimented with computer control of the humble carb, trying to squeeze out every last bit of efficiency and reduce pollution as much as possible. [NeXT] happened to own a vehicle fitted with AMC’s Computerized Engine Control system, and decided to see what made it tick.

This was easier said than done due to choices made by Ford, who manufactured the engine computer for AMC. Unlike modern ECUs which usually feature a metal case fitted with rubber gaskets, the CEC computer was potted in epoxy. [NeXT] was able to de-pot the circuit board by placing it in a stock pot of boiling water, and then slowly peeling the epoxy away.

With the potting removed, it was possible to begin reverse engineering the board. The main microcontroller is an Intel 8049, of the MCS-48 family. The board uses through-hole technology, and only features a handful of other small ICs.

It’s always interesting to look back at forgotten technologies and see how things were done in decades past. [NeXT] hopes to keep working on the project, intending to dump the ROM from the CEC module and build a replacement computer with an Arduino. It’s possible to build your own ECU from scratch, so we’re looking forward to seeing [NeXT]’s AMC Eagle running on modern silicon real soon.