I have a 1979 XJ6L 11 the car sat for around 7 years,I have replaced the fuel pump fuel tanks and cleaned and flush the fuel sistum removed and had the and cleaned cleaned fual injectors and line.
So and car will start but will stay running 3 or 4 sec.
I did run the fual pump off a constand power same problime.
Ron

 

Thanks for the help,It was the fual pump relay on the firewall took it off took it apart and cleaned it and the car runs ggggggggggrate lots of smoke after 7 years but cleared up fast.
Ron