Originally Posted by tabetha
Priming is only there to ensure suffecient start pressure in fuel rail, and it does it only sometimes depending on where the engine has stopped.
If it is close to a TDC sensor notch this will be picked up, and cause a RUNNING signal to be received, if not it wont.
Most engine stop in the same postion but not always, this is why they oftenm wear a particular point on the ring gear and give trouble with worn teeth on it.
tabetha
OK with Tabetha.
2 strategy are apply by ECU : cold engine and very hot engine.
With cold engine, and contact on, fuel pump start just during 1 or 2 seconds, just to obtain suffisant fuel pressure in the rail. And it restart as soon as engine crank is in suffisant speed.
With very hot engine, and contact on, fuel pump start during 10 seconds, to obtain a big flow on fuel rail to avoid vapor lock.
You can easely check this with disconnecting WTS and shunt connector directly on (use cutting paper clip). This shunt is , for ECU, same than very hot engine.
(resistor = 0)
Regards.
Claude