|
83Z! In an earlier post in this issue you have made an interesting discovery in that DME relay (second half of it) cklick at the same time as the starter cranks. If we follow the current flow diagram we can see that pin 4 in DME gets +12 volt together with cranking voltage to the starter from the ignition key in START position. Inside of DME the electronic circuits are activating DME pin 20 instantly to ground thereby activating this part of the DMR relay.... as long as key is in cranking position. This is to make a speedier start of fuel pump to build up pressure to the injectors and make engine start quicker. Now, if engine starts while cranking we usually let key go back to ON position when we realise that engine is running. In this situation the starter AND pin 4 on DME looses +12 volt (current supply). But when engine now is running, electronic circuits inside DME takes over the grounding of DME pin 4 thereby keeping DME relay (fuel pump side) activated. I have not understand this until I got an electronic diagram for the DME computer and searched its functions. So, as a conclusion: you were right hearing the click from DME relay and fuel pump start humming at the same time as key was turned to START position. Of course, one can refuse to accept this, as in a good starting engine, there is such a short time between cranking and engine is firing up.
If this circuit (DME pin 4) is cut off by a broken wire, corroded connectors etc, engine will
nevertheless start but will need longer cranking to start. I assume that cranking speed is enough to make speed and referece sensors to áctivate the DME computer.
|