a 928 owner in the Netherlands had this problem:

1987 928s4, No start
- no injectors clicking
- LH ok, swapped and worked without problems (even swapped together with EZK onto another car)
- EZK swapped and worked fine
- Ignition worked, sparks show at plugs from both sides
- temp2 is about 3k ohms at both sensor sides at 20C
- fuel pump is not activated, but runs when you bypasss the relay, still no start
- relais LH, EZK and Pump swapped, no difference
- spray fuel in the MAF and the engine briefly starts
- no alarm start immobiliser existing
- alle electrics seem original

Turned out to be the kickdown relay. It caused a load on the speed signal between EZK and LH, causing the LH not to see a speed signal and thus not activating normal operation but stay in standby until the engine starts to turn. No injector puls yet so no fuel, so no start.

Pulling the #15 relay immediately made the car start.

ps: Funny that the EZK fires the plugs... making you think things are ok with index pulse and such.