Hi, I am working on a friend/customers 1985 XJ6 (6cyl) that sat of 8 years I got it to run and drive ( I had to Hotwire the fuel pump from the relay and put in 6 spark plugs, wires, cap and 1 o2 sensor). Then it started. It idles a bit shakey but not too bad. Problem begins when I turn it off it refuses to start again. it has spark, air, and fuel but, it won’t start unless it sits for a few hours.

PS I work on antique cars that are carbed I am not used to fuel injector cars.

 

If it’s been stood awhile rust in tanks get into fuel filter restricting flow. New fuel filter and clean pipes, also consider extra inline filters. Pump might need changing as well.

 

I agree that the fuel system probably needs attention. Pull the fuel filter and empty the contents into a clear container. What you see will dictate your next steps.

Cheers
DD