The fuel pump relay also powers the ECU on S1 Roadsters which I found out the hard way.
On my 3.7l Roadster the fuel pump relay was an issue. Dirt cheap to replace.
If you have 3.7l car try pressing down the relays. If they move that could be the cause, in Belle's case they seems to vibrate loose so they are taped down.
The AC relay can be used as a spare.
