XJS 1989 will not start

I recently replaced rear heater hoses and a faulty oil pressure sender. I have the Magnelli ignition so had to remove upper and lower coils to get to oil Sender unit.
Now the XJS will not start after replacing everything. It want to but then the starter stalls. All lights come in as expected but no ignition. I noted that each coil wire has three wires and I am wondering if I put them on incorrectly but no matter she will not fire and Always ran like a depream until heating issue once. I am at a loss and need some help here. Michael Jacobs

Not quite sure what you mean here.

Is this a case where the starter cranks the engine…but the engine will not start?

Or, the starter won’t crank the engine?

Either way, a good place to begin is to very carefully retrace all your steps and look for any broken wires or connectors.


No the starter cranks the engine but the engine seems to be misfiring or trying to fire but wont. I double checked the distributor leads to coils and they seem fine but the connection to the coils with the three leads may be wrong.

The upper coil connector should have white/black wires and a yellow identifier
The lower coil connector should have white/brown wires and a red identifier

I can’t remember what form the “identifier” will be

Someone here will know


To expand on Doug’s note, white/black is B Bank (the coil that goes to the offset ignition coil wire slot) and brown/white goes to A Bank - being the traditional center ignition coil wire slot.

The markers are a red band on A Bank and a Yellow on B and are simply pieces of tape, which may or may not still be there - but the wiring colors are your final confirmation.

I reference the banks and the coil / wire in its location on distributor cap vs. coil location, as many coils have been replaced by now and wired with either the top or bottom coil in a swapped position - which is okay - as long as the other requisite bits are swapped too.

I am most grateful for the responses. I believe I may well have the three wire leads in the wrong position. When I removed the coils to remove the tower I disconnected the upper coil T the distributor and the lower coil lead I left in place so I believe these are right now I need to check the three wire leads, but one s monger than the other which I assumed was the upper coil. I must be wrong here. The engine cranks but it’s like wanting to fight the starter. Can you tell me if the three wire leads are available. I can see small cracks in mine. Michael

Sorry to all but I jumbled the response. I took one lead from the upper coil off at the distributor at the offset lead and the other at the lower coil. I do not have colours on my coil leads as the whole set was replaced some time ago. I believe my problem is at the three wire leads. One is much shorter than the other and I believe that should go to the lower coil, but I may be wrong. I also noted that I have small cracks on the plastic in the three wire leads and I am wondering if that is an issue and if they are available for replacement. I also noted that when I look into the coil connection on the three wire lead at the single pin I noted on both that the plastic pin separator was cracked and or broken off. Again I have ordered two new coils. My apologies for any confusion. Michael

There is an old post on this forum. The V12 forum. Use the search magnifying glass at the upper right of the page and type in "source for marelli coil connector. Post by RCielec dated 12.2022. See if that is the connector you need. SD Faircloth

Thank you so much. I have had my XJS for some 30 plus years now and it only has 114000 Kilometres on it. The process of changing hoses and an oil pressure sender has shown me just how difficult the access really is on the Jaguar XJS V12. Michael

So…for myself and the collective, does that appear to be the connector you need ? SD Faircloth

I have not found it so far, but will report back. Michael

Attached is a picture of the distributor and coil area of our 1990 XJ-S convertible with Marelli ignition.

The black identifier on the white upper coil wires is circled in teal and a brown identifier on a white lower coil wires is circled in yellow. The shorter wires go to the upper coil and the longer wires go to the lower coil.
My car has some cracking in the coil wires that I have temporarily repaired with liquid tape and black electrical tape to cover the exposed conductor. I plan to rebuild the coil wire harnesses once I complete some ongoing work on my other two Jaguars.


Thanks so much, this helps a lot. The longer wires go to the lower coil, must be a Jaguar engineering decision. I also note your wiring harness is on top while mine is at the bottom on my coil position, easily charged though. Michael

Success on the retire. The car fires right up but goes to 3000 plus RPM. I shut it down immediately and checked the connections on the throttle switch and the other switch on the opposite side. Starts right up but again 3000 RPM. Any clues. Michael

Hate to ask the simple question, but is the throttle open ? Did you remove an air box and filter and observe the position of the butterflys ? If they are closed and set at .002, I can’t see the engine getting enough air to sustain 3,000 rpm. SD Faircloth

No found the cause thank you, vacuum line. Now purring at 800 on idle and running well. Thank you for your input. Michael