I have a similar problem to Lesxk8 but rather than hijack his thread I though it better to start my own. It appears that the ecm isn't switching the fuel pump relay. Pump is ok and I can run it with a jump across the relay base terminals. The relay has been swapped with another and no change. The only code I am reading is low fuel pressure. The problem showed when I went to drive the car out of the garage, it fired and ran for a second or so then died, I guess as the residual fuel pressure decayed. I have checked all fuses, I did find one blown for the security sounder circuit. I have disconnected the sounder and replaced the fuse, I am now wondering if the security module is stopping the pump from running because the sounder is disconnected but if anyone has any suggestions I'd be grateful because I'm running it of ideas. 

Ok, tried with the security sounder reconnected and no difference. I have removed it now to see if it's repairable but that's for another day.

i put a link wire across the pump terminals in the relay base so the pump runs all the time and tried to start the engine, no go. It turns over ok but isn't firing so the problem is effecting the injection and or ignition too, :( 

Did get a P code, 1230 which is fuel pump relay failure! I know it's not a faulty relay because I've both tested and substituted it.

Finally the inertia cutoff switch seems to be pressed in as it should be.

 

On a 1999 xk8, where is the cutoff switch?

is there an early and late 1999, where the switch is in 2 locations for early and late?
hunted around the rh kick panel but couldn’t find it.

I found it.

fuel pump cutoff is on the left side of the dashboard not the right.

Hey Dazed,

took the piping off the throttle body and added a little gas in the throttle body and runs till gas is used up.

my car has the same problem as yours. Took the Gas filter Line off and fuel drains by gravity, so not the filter.

removed the Fuel pump fuse and the fuse Gets power from the key in start. Then checked  cutoff switch and it’s down, then at the pump there are 3 wires.  black with a green tracer, Red with a green tracer, 
Blue with a white tracer.

to the right of the center of the tank is a white connector.

i pulled that apart and checked for volts.

no volts on start.