I would assume at this age yours is EFI and not MFI ?
That being the case I would expect it to prime on each key on to position 2(run), but would in any event put the pump on in the start position.
I'm sure the pump is external on these ?, if so simply put a live onto it direct from the battery, if it now starts then you know it's a ecu/wiring/relay fault.
Have you checked for a spark though when it doesn't start just to rule this out ?
tabetha