my 1995 xjs was running perfectly until the other day. returning home i smelled burning plastic and apparently there was smoke coming from underneath the motor. i made it home and stopped the car and checked the engine. i could find no trace of anything melted or burnt. oil check was ok but the coolant was very low which i have since topped up. the car turns over but will not start. there is a spark at the plugs. what could of burnt out that i`ve missed? the fuel pump is working. could it be a sensor that has burned out? have i broken my car? there were no warning lights either before all this happened. any ideas much appreciated. thanks