If I leave my bike engined car for a few days, the fuel pump ticks away for a few seconds before stopping. If you switch the ignition on when the car has been stopped for a few hours, it doesn't.

Is this because the fuel evaporates out of the float bowls and needs to be topped up?

yup

Also some ECU's know how long car has run etc so will only let pump run on/ pre run if required.

Won't the line pressure have dropped sufficiently (in a fuel injected setup) enough over a few days for the pump to trigger when restarted? I think evaporation is unlikely in a sealed system, but back pressure (balancing) is more likely.

Steve

[Edited on 28-3-06 by Hellfire]

the float bowls on my carbs are not sealed. the main jet opens out into the venturi of the carb and the float bowl breathers vent to atmosphere. I didn't know that fuel would evaporate that quickly.