Hi guys,

I'm working on a 1991 JAGUAR XJR-S 6.0 V12 Coupe,

The problem I've got is, it's currently not starting at all.

Prior to not starting, it was always difficult to get it going, once it did get going it had a terrible back fire.

I've now replaced the coil, now it's still not starting.

Checked for spark and still nothing.

Checked the ignition wiring and it's showing 12v where its meant to be, but it's also 12v on the coil output where it meets the spark plug? Any ideas would be hugely appreciated

Picture below is prior to replacing the coil

 

Since your car uses the older Lucas ignition module (black box, red sticker), I'd suspect it or the pickup in the distributor. I'm assuming the early 6.0 used a distributor pickup, but I'm not sure. That black module should be the same as that used on the earlier HE 5.3 engines. It is based around a GM HEI module, but also has a capacitor, a Zener diode, and two resistors inside. I'm attaching a diagram. It is common for the GM module to fail, and the capacitors and zener diodes also fail. If either the capacitor or the zener short out, the whole module won't work. The capacitor is not necessary, and can be disconnected. The zener provides additional voltage protection that later GM modules don't strictly need. Both were Lucas parts, not available elsewhere. There is a video on YouTube showing how to repair the entire black module, with substitutes for the zener, and what GM module to buy. Use ONLY genuine GM modules, as others are junk.

Jon

 

Thanks Jon, so am I right in thinking I can bypass the module

 

ClassicCarNewbie,

That really doesn't look like the engine of a 1993 XJR-S. It looks more like a pre-facelift XJR-S setup. Can you confirm what year the car is?

Paul

 

Yes my apologies, I was given the wrong year. I'll amend now

Year 1991
Make JAGUAR
Model XJR-S. 6L

Any help would be greatly appreciated

 

No, the Lucas unit needs to work or no ignition.

 

Please post some close ups of the wiring to the Lucas amp and the coil. It does not look right to me in this photo:

 

 

The HT king lead looks rubbish.
I do not think the Lucas amp outputs are connected to the coil positive, I can only see the white 12 ignition feed wire connected.
There are FOUR wires thazt exit the amp:
One goes to the coil positive (I THNK it is white)
One to the coil negative (I think it is white with black stripe)
One drives the techo (thin white with blue spiral trace)
One goes to the ECU, the white wire and is connected into the loom going rearwards.

I cannot see the auxiliary coil conections anywhere

 

It looks also that the FTS vacuum piping is not connected.
You appear to be connected at one end. Blue in my pic

 

Does this mean it is a ZYTEC car, Paul?

 

Those wires that go to the bolt on the ignition amp look wrong to me. That bolt is just ground.

Here’s what my ‘87 looks like. There are two wires on top of the case, they plug into the side right where they are.

 

If this is an oroginal xjrs, it would be a Zytec car no?

 

Yes, but it still uses the Lucas ignition amplifier.
The distributor is unique to the XJR-S with dual Hall effect sensors. One is for engine speed, and the other for cylinder synch. They feed the ECU directly, not the Lucas module. The Lucas module gets its signal to fire from the ECU. The Ecu appears to provide the tach signal, not the Lucas module, unlike other non-XJR-S Lucas equipped cars.

Here is a link to a copy of the XJR-S technical support manual. It provides wiring diagrams for the engine management system and other info that should help you troubleshoot.
http://jaguarclubrussia.com/images/k...JRS-1992--.pdf

Jon

 

If it's a 6 litre car, then it's a Zytec setup.

The bit that's confusing me is the coil. And not just the fact that the king lead is a real mess, as mentioned. AFAIK, all the pre-facelift 6.0 Zytec cars used a bespoke hi-power coil that isn't shaped like a traditional coil. But the coil now fitted on that car (and the previous coil in the pic) look like basic standard coils? The confusion is made worse by the fact that the coil seems to use a fixing bracket for that type of coil which seems to have been fitted from new. Strange..

And again, as mentioned, the wiring attachment on the bolt on top of the Lucas box doesn't look the same as other 6.0 XJR-S that I've seen.

Below is a pic of the engine of a pre-facelift 6.0 XJR-S, showing the bespoke coil, the wiring on the Lucas box and the pipe attachment at the end of the LH inlet manifold





So, at the risk of being a pain, we're definitely talking about a 1991 pre-facelift 6.0 car, are we?

Paul

 

Earlier inlet manifolds.

 

rgp,

Those are the manifolds used on the 6 litre up until the facelift cars came out. So they are the ones that would be on a 1991 pre-facelift, AFAIK.

Paul

 

like mine, a sort of comb over, :>)