bosch pump hissing air.

[fieldofrob]

that's a breather at top of pump to vent pressure.

how can you tell it's leaking air is it hard to start or something?

hey bud, yeh its a bit smokey on startup, the inline filter is full of air, I can clamp fuel line and loosen jubilee to let air out as i prime it but within couple of days it will be empty of fuel.. I can't then think where the leak would be, I've replaced everything in the engine bay, the sender unit in tank seems tip top..