No speed signal ?
The kick down relay is fed of that rpm feed from EZK to LH. The rev counter (tach)
is also fed from the same point.
Those pulses are required to wake up the LH, so it energizes the fuel pump relay and also pulses the injectors.
If your tach flickers when cranking the engine, then that would usually indicate all is well with the pin 13 EZK --->> pin 1 LH feed.
A helper should also be able to hear the fuel pump whine when you crank the engine.
Then confirm that the injectors are pulsing when cranking, as Bill has suggested.
This picture shows the signal path of the speed (rpm) signal for a 1988 928S4. Click on the picture to see a detailed view.