A quick update. Today on a whatsapp video my great nephew aged 2 said he wanted to drive Duncle Dohns Morgan followed by lots of beep beep & brm noises. They are coming to us once they can so I thought I should test if once started and released the start button engages the starter. The answer is it doesn't which is one up on the ignition switch.
I still love the drama of pressing the button & it adds to the grin factor immensely.
Interesting findings John. The standard ignition key start places a momentary +12 volts on pin 16 of PCM to initiate start sequence once clutch is depressed, via a shorting link in otherwise redundant start button socket. You don't need to hold key in start position therefore, just a dab is needed.
When start button is spec'd or added the sequence is longer. Start button sends momentary ground to BCU which it electrically translates to momentary +12 volts and passes on to same pin 16 on PCM, so again just a dab is needed.
Because link is removed to fit latter the key start is disabled but I see no reason not to leave it functioning (as backup) by renewing the loop between pin 2 and pin 5 (white/red wires) on loom side of start button socket.
