XJ12 Non starter
 

Before too much gets too confusing, slip down ONE section to the XJS Section.

I have a "sticky" at the top about what you are seeing, and maybe it will assist.

Bugga.

1st coffee still brewing, so I will think some more and reply later tonight, our time.

Fire is from what, if you know, as that could be the key to NO start.

This list could be LONG.

If the pump is running whenever the Ign is ON, that is possibly a simple bridge in the relay socket, and rather common when diagnosing fuel pump issues. The ORANGE wire of that same socket is the EARTH for that relay, and controlled by the ECU. Without that circuit, the timer for the 2-3 seconds of pump run at each Ign ON is inop.

NO Injector "click" as TPS is moved from Idle to WOT with Ign ON is NOT a good sign.

The CTS (Coolant TempSensor) may NOT be supplying a feed back, and it will NEVER start with that fault, soooooo, unplug the CTS, use a paper clip to bridge the terminals IN the socket, as this will fool the ECU to think a HOT engine, and it should start.

The TPS is dead, COMMON.

The shielded wire (Coax for some) from the Ign AMP, to Pin #18 of the ECU is broken, COMMON, especially when fiddling has taken place.

EFI loom, in the bottom of the "V" is shorting internally, COMMON.

The EFI resistor pack, not sure where it is on a S3, has very dirty contacts on its multi pin plug. MANY threads on this in teh XJS section, mainly by Greg in France and Orangeblossom.

Thats enough for now, as its beer o;clock here.

As Grant said, and as his examples indicate, the 'could be' list is long. You just gotta pick a jumping-off point and dig in.

I'd go with jumping the CTS terminals. That's a really easy place to begin.

After that, check the shielded wire. Lots of info in the archives.

Cheers
DD

Same as on the XJS: RH side of the engine bay, way forward, down low and out of sight :)

Cheers
DD

And check for 'key on' supply voltage to the injectors. Pink/black wires.

Cheers
DD

Ok, good. That's something. Check this item off the list and keep going. :)

You'll have "+" voltage on both wires until the ECU grounds one of them

Now jump the terminals on the CTS connector.

Then clean the connection at the resistor box.

Then check the shielded wire.

You're finding out what isn't the problem. That's how it goes with these cars.

Cheers
DD

Ok, you're ahead of me on posting !

Just keep going

Cheers
DD

I think there be an EFI loom issue.

Even with the Shielded wire AWOL, the Injector click when the TPS is rotated from Idle to WOT quickly, should still be present. BUT, if there is a loom issue, NO.

I would also bridge the ATS (Air Temp Sensor) socket. MAYBE, and yes, MAYBE the ATS and CTS are wrongly plugged, been there, took days to find that, and that was before Forums and computers, whoopee.

Attached is a Pin out for my 1985 XJS, basically the same as your beast.
Also an EFI schematics that has got me out of troble many times.

You say it runs with stuff sprayed up its snouts, so simple, the fuel aint getting through the Injectors.

Ign ON< the Injectors SHOULD NOT spray, Repeat, SHOULD NOT spray. If they do, or did, then the EFI loom is #1 on my list, followed closely by a TPS out of range.

Injectors DO NOT spray every time the key is turned on, God forbid, the thing would fill with fuel in a heartbeat.

The CTS and the ATS SHOULD both have the same 2 pin Injector style plug. Thats why they can be mis-plugged sometimes. If the CTS has 2 seperate spade terminals, without that Injector style plug, then someone has fiddled, and maybe that loom, which travels aft, via the ATS has also been messed up. That pin out will clear that up in a few minutes.

Forgot, its been 41c all day and now at 9PM still 38c, so declared Beer O'clock at 9AM.

This attachment for checking and adjusting the TPS may well be worth ticking off the to do list, as it may be PART of the cause of the NO running.