Modern Vespa

I have an incredibly annoying intermittent fault on my 2017 Sei Giorni GTV. I turn the key, the fuel pump primes, I press the start button, nothing happens. I've changed all the relays, cleaned the connector blocks, start button and the side stand switch.

I've put a meter on the far side of the connector block behind the glove box and can confirm the button is connecting the two wires as it should. Nothing happens.

And then for no reason it's completely fine for a few days until it does it again.

It's driving me nuts.

The starter relay coil gets 12V direct from the brake light switches. The starter button feeds a 12V signal to the ECU. The ECU (if happy to allow start) then grounds the relay coil, so energising the relay.

So check the ground side of the coil does indeed get grounded.

I had a similar issue with my 2006 GTS. Turns out it was a bad brake switch behind the left side lever. Next time it happens squeeze the right side brake lever and see if it starts. Replacing the switch just involves opening up the headset. Not too difficult.

w.