Thread: ECU Problem with 1987 RRC?

From memory the ECU controls little more than injection time. The fuel pump is switched on by the starter motor circuit and also the air flow meter. If you manually move the vane in the air flow meter (with the ignition on) the fuel pump should run. Its relay is under the seat next to the EFI relay together with its fuse. Use your test light on the white/purple striped wire at various points from the fuse, relay etc all the way back to the pump to check for power on cranking.

The brown/orange stripe wires to the injectors should not flash noticeably, it's the 12V feed from the EFI relay under your seat. The flickering may be due to starter current varying the voltage. The yellow wires should pulse towards the negative as they fire the injectors. The only input that the ECU has for a rotation signal is the white/black stripe wire from the negative side of the coil. There is a relay hanging near the air flow meter that interrupts this signal to the ECU when high vacuum is present at a vacuum switch on the drivers side of the engine. The relay can be bridged out for testing, some people leave it out entirely but it uses a little more fuel on over run. You can test for the rotation signal at the ECU with your test light at the black/white stripe wire there.