wwest

1988 Carrera. Diagram shows DME relay armatures connected directly to battery positive, through connector "NR173". No voltage on either DME relay armature, where does the power wire come through the "firewall"...trunk wall...?

wwest

1988 Carrera. Diagram shows DME relay armatures connected directly to battery positive, through connector "NR173". No voltage on either DME relay armature, where does the power wire come through the "firewall"...trunk wall...?

"..no voltage.."

I was wrong, had voltage to the primary DME relay armature, poor/cracked solder joint to second relay armature where by pure happenstance I was checking for battery voltage. Battery to DME terminal 30 circuit was good all along.

Primary DME relay closes with ignition switch, secondary (fuel pump, O2 sensor heater) does not. Fuel pump runs if I depress 2nd relay armature manually.

Energizing the fuel pump manually is of no help since ignition coil isn't being "energized" while cranking, constant full battery voltage on both coil terminals.

So now I have to consider the speed sensor or the DME ECU.

Both sensors, speed and reference, measure ~960 ohms at the ECU connector.

While cranking I get 2.8-3.5 volts AC across ECU pins 8-27 on ECU circuit board.

Replace speed sensor anyway, first, or go for broke, EXPENSIVE DME ECU...??

Wishing I hadn't loaned the 78 Targa to nephew, much simpler troubleshooting.