Hey all. Quick question. I disconnected the battery on my '82 XJS while I was working on the engine, and I go to reconnect it and the car won't start. I've isolated it to the fuel pump, which apparently isn't pumping fuel. It worked fine before I unplugged the battery. I'm worried that either a) the fuel pump shorted, or b) the inertia cutoff switch triggered. Anybody know if there's some special thing I have to do to get the fuel pump started if it's just the cutoff switch?
Thanks!

 

First of all check the fuses and relay to the fuel pump. As for the inertia switch tripping why do you think that? As far as I know all you need is power to the pump to get it running. Is your car equipped with a security system and is that the reason it might not be working?

 

Hard wire the pump to the battery (through a suitable inline fuse) to see if it will run.

I am currently in the middle of a tank out / new fuel pump escapade and this was how I finally diagnosed my pump was dead (This was later confirmed by my Jag specialist mechanic)

It seems the pumps can just suddenly fail. I drove my car at 3pm and it was fine, but at 7pm it would not start as the fuel pump had died

 

Hard wire the pump to the battery! Brilliant. And if the pump's bad I'll know right away.

Thanks!

 

So I hardwired the battery to the pump and the pump fired right up. I went back to the inertia switch and wired it out of the system, so I don't have to worry about it (if I flip my car I'll just burn to death).

Thanks for the tip. She still won't start, but at least that part of the puzzle is solved

 

Mmmmm, 82 V12, has I reckon a 6CU ECU in the boot, they are well known for fuel pump circuit issues. The fuel pump relay, in the black socket, in the boot has an Orange wire out of that socket. Earth that orange wire, the section TO teh relay of course, that will remove the ECU from control of the pump relay, so the pump will run whenever the ignition is ON, be careful obviously.

The fuel pump relay is "switched on" (powered up) as such be the "Main relay", thats the one in the Red socket.

 

Hey Matjohns,
how did you wire out the inertia switch?
mine keeps tripping, I'm trying to locate a new harness.
I would like to temporarily bypass my switch.

 

So Im having some intermittent pump issues and would like to do this but which way do I ground it? Do I cut it off at the relay and ground the wire coming from the wiring harness? Or do I cut it off at the harness and ground the wire coming from the relay? I hope that makes sense.