I have tracked down the fault. The power to activate the relays comes from the ignition switch. This goes thru a relay called EFI main switching relay ( this is what my book calls it) but I do not know where this relay is. Any help would be greatly appricated.
According to the S57 manual it’ll be on the LH side of the LH component panel under the dash. Look for orange/pink, white/orange, and white wires
Cheers
DD
No relays under my dash with any of those colored wires in my xjs
the Diagram I am looking at says the wires are –W-- x 2—WO—OK
There is no relay under my dash drivers site with those colored wires and there is no relay in the location shown on the detail 4.2. I only have main and pump relays in trunk but one manual shows the EFI switching main relay in the trunk
I have gotten the starter to work but will not run with out pump running. Have power from switch but no ground at coil so relay not work but used a jumper to run starter. Now I got the fuel pump relay to buzz but no pump run. Have tested the pump with 12 v and it runs. Have a new inertia switch coming but not finding the EFI switch main relay. My model year is just befor 1988 1/2. I think if I could find this EFI switch main relay I will find my problem.
I have a diagram which shows the EFI ECU in the trunk
Just to clarify, this is a 12 cylinder car, yes?
And I’m wondering if there might be some model year confusion, perhaps? It wouldn’t be the first time. The relay in question is not shown in my 1987-older S57 schematics but the S57 guides always appear to be USA-centric, and USA model year designations for the XJS are sometimes baffling.
Cheers
DD
Only fuel pump and main relay in trunk in my xjs
This is a V12 engine with no modifications to the electrical system (relays, switches etc not removed or relocated except for the radiator fans)
I am really stumped on this
Mark’s wiring diagram clearly shows that the EFI main relay is grounded using the inertia switch. You say you “have an inertia switch coming”. While you wait for it to arrive, here is a n easy test you can perform.
Below the inertia sw. is a connector. Unplug it. You will see a black wire (ground) and two orange with black tracer wires joined together. Attach a jumper wire to the O/B terminal on the connector. Ignore the black wire. Turn on your ignition without trying to crank the engine. Touch the loose end of your jumper wire to a decent ground. You may hear a click. That would be your relay if it is close by. You may hear the fuel pump run for a few seconds.If you hear anything power up, then try to start the car. If it starts, keep watching for the mail to arrive, as your inertia sw. is N(F)G. Let us know the results!!!
I removed the instrument pod to see if possible that would allow me to see the EFI switch main relay but nothing. Checked the trunk again to see if this relay could be hiding there and found a broken white/orange wire and repaired it then tried to start the engine - everything came to life a little rough ( possibly due to sitting over 4 weeks). Will put everything back together and hope all is well. Still have not found the missing relay.
Will save to new inertia switch for when it will be needed. While I let her run I pulled up the plunger in the inertia relay and engine stopped.
While working in the trunk I had the fuel pump laying on the carpet and when it ran it makes no sound but when it was mounted in the car trunk in the past I could hear it run from the drivers seat, interesting
Glad to see that you are getting somewhere! Perhaps you could make sure that the fuel pump is not touching any sheetmetal , transmitting the sound. Good luck!
