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
yes it will prime to ensure sufficient rail pressure for start up, but the engine will never "always " stop in the same position or anywhere near ????
the ECU controls the fuel pump relay, when the ignition is turned on the ECU supplies an earth signal to the pump relay for approx 5 seconds. when the ECU receives an engine start signal the pump relay is then re activated...
when the ECU is turned off " engine off " the relay is turned off...
if you have a problem with it running " lean " or holding back, melting plugs, get it to a rolling road to have it checked before it melts a piston....
if you have a fuel pressure gauge, you should see 3.5 bar @ idle ( vac off )
when you are on full boost you should see 3.5 bar plus what ever boost you run ( 2 bar boost + 3.5 bar nominal pressure = 5.5 bar fuel pressure ) vac on
if this is OK it could be the fuel map ( injection timing / duration )
if you don't have an O2 sensor boss in the exhaust front pipe, get it done for the set up to be sure...
if you are having pressure/ pump problems don't forget that poor connection's ( inc alarm / immobilisers ) will increase the resistance in the circuit and reduce the amp`s to the pump ( reducing the flow out put )
best of luck.....