Jaguar Repair: XJS-C 1984 3.6 Starting problem, xjs v12, lucas ab14

Question
QUESTION: Howard

I have a 1994 XJS-C 3.6 which has been garaged for at least a year, perhaps longer. At the time of placing it in the garage it was running well and would always start first time.  On a regular basis I would start the XJS-C without problems. On my most recent attempt it failed to start – having checked basics I found that the fuel pump was not starting – you can normally hear it in the boot. This turned out to be the Bosch relay 0 332 014 13 (is this the pump or main relay?) I swapped one from my XJS V12 and the pump started.

This however this did not resolve the starting problem – which seems strange as previously mentioned it had always started first time. I also swapped the relay 0 332 014 12 but this did not help either.

I checked for spark – and there was none. I checked the main relay inside engine compartment – there was power. I checked the coil and that seemed to be suspect – so I changed that, but still no spark. Checked connections from coil and all seem ok.
The injectors seem to fire, I can hear clicking.

I stepped back from the problem for a few months as it is too easy to get sucked in when trying to resolve a problem.

I recently checked the Lucas AB14 Electronic Ignition Amplifier connections – specifically the removable cables going from the amplifier to the coil. These have been played with by a previous owner and when touched the cables where obviously not stable. There was a braded (earth) connection which was not connected.

I have tried to find a diagram or drawing which will help me understand how the cables should look and be connected – but so far without success. Could this be the root cause of the non-start and no spark?

Regards
Rae

ANSWER: Hi Rae,

Sorry, I have no experience nor info on that engine combination in that car. (always wanted one though)

However, I do have experience on most of the Bosch injection systems with (Lucas stickers on them) and all of them use the ignition pulse signal to start the injectors and use all the other sensors to control the "open" duration for fuel mixture.

The fact that you have injector operation, tells me that the primary of the ignition system is working and if you have no spark, it is in the secondary of the ignition (coil, cap, rotor, wires etc.)

I would test the coil secondary first. Just clamp your timing light on the coil wire and spin the engine to see if you have a pulse. If you do check the cap, rotor and plug wires.

I don't know that car but if it has the same problems that the US versions of the Jaguar had about that year model, even though the battery may seem up, connect another known good jumper battery to the car as though the car battery were low. And try to start it. If it then starts, you just need a new "Deep Charge" battery (diesel battery).

Howard

---------- FOLLOW-UP ----------

QUESTION: Howard,

What a prompt and detailed response. I thank you for your assistance.

I tried so carefully to get the facts correct but did you notice the deliberate mistake? - it should be 1984 xjs-c.

The battery issue, as you said, is a problem with later Jaguars, which I experienced only last week with my XJ8 1998. I have to say, I have replaced the battery on the XJS-C with a known working one - from my XJS-C V12.

I understand what you are saying about secondary coil , cap, rotor and plug wires. These were all recently replaced.

What is the role of the Lucas AB14 in the process? I'm  not sure how it should be wired into the coil. As I mentioned, its currently not fully wired.

Regards

Rae

Answer
Hi Rae,

If you have the AB14, it is the amplifier that takes the signal from the pick-up in the distributor and triggers the coil on and off. Inside the AB14 you will find a GM control module.

There should be a socket in it's side to have the pick-up plugged into and a harness with two wires (white wire and a white w/black tracer wire) The white w/black tracer wire plugs onto the (-) side of the coil and the white wire plugs on to the + side.

The amplifier does not supply power to the coil so you still need a power supply from a relay and most likely a resistor is connected to the coil. Most of the US versions used a resistor and a low voltage coil.

Howard