fuel pump relay is next to the ecu on the later models
(behind the plastic cover to the right of the GOGO pedal)
it's a very common problem
also worth mentioning the plug that powers the pump itself
having owned 4 carltons,2 had poor connections that stopped the pump delivering gogo juice
i currently have a fuel pump relay bypass loop fitted that i use....
1: when the carlton has not been started for a couple of days ,
(makes sure there is pressure in the fuel rail by activating it for a few seconds.)
2: if my carlton won't start , activating the bypass allows me to listen and make sure my fuel pump is running.
the coolant temperature sensor used to be a common fail too
also, check all the earth terminals are good
beef up the earth to the coil with thicker cable
beef up the earth strap between the alternator and cam housing
(the original is way to thin and gets hot )
as for roadside diagnostics
minimal tools and very little skill/knollege are required to ...
remove a spark plug and check for spark or check if fuel is being delivered to the rail
modern "mechanics" rely far to much on computer diagnostics
have you done a "paperclip test" ecu diagnostic after your carlton decides it needs an unscheduled rest ?clicky topbuzz diagnostic