Ignition problem
 

Hi there, im running out of ideas with my V12 XJS. (5.3 '88). I was warming her up before driving to France, she was running very smoothly, as I was about to put my suitcase in the car the engine just stopped. I cannot get it to fire back up again. The electrics and starter motor are all working.
I had the breakdown service check it out and he thought it was the Ignition coil that had died. I have bought a second hand one from a running engine and this has not sorted the problem.
The other strange thing is the fuel gauge on the dashboard is reading zero, and I know there is a full tank as I had filled up the day before. Are these problems related?
Also the guy at the breakers yard suggested it might be the ignition amplifier as this plugs into the coil.
There is power going to the coil but nothing coming out, is it worth me fitting a new amplifier? or can anyone suggest any other thoughts.
Thank you in advance.

And maybe someone siphoned your tank overnight.

You could spend hours on this just to find out that the car is out of gas.

I did consider that and put a 10 litre green tank in just incase, but it was in a secure underground car park so unlikely.

I agree with Plums, that would be my first check.
If you find it does have gas, then I would be wondering if there was a bad ground causing both problems.

Is it normal though for the engine to suddenly develop a fault like that after its been running faultlessly beforehand? I cant help thinking it is a fuse or electrical component that just died but myself and the AA guy both came to the same conclusion of it being around the ignition coil/amplifier? How many systems are there in place to create the spark that goes to the distributor that I could test?

The amplifier has a module inside which is normally the problem. They can "just die", it happens. I use an Echlin TP45B or an ACA IM113 module when I need to do one, and mine was 3 days ago for equally a strange a reason as yours, just died in the driveway, damn.

The electrical section of the ignition switch is another weak link due to age, and is easily cleaned/repaired. I have done many over the years.

The fuel pump relay (in the boot) in the "black socket", can fail and the fuel pump stops working, which I doubt is your issue.

Just had a flash, scary on any day, has for some dumb reason the inertia switch tripped, or just gone flaky, try resetting it, long shot, but what the heck. Mine did wierd s&^t and I by-passed it years ago.

There are no fuses etc in the ignition circuit that I know of.

The fact some dirt bag took your fuel is real, but with mine after I syphon all I can out of the beast, it still has about 10+ ltrs in it that are usable, and I dont reckon you would use that much warming it up???.

That takes me back to the ignition switch electrical section not wanting to go to France, haha.

Thanks for that info, I agree, I think the Jag just didnt want to go to France!!
Where would the inertia switch be?
Fuel pump is definitely ok, im still baffled why the fuel gauge reads empty, theres definitely loads of fuel in the tank.

I am RHD, and that inertia switch is under that silly plastic cover that you hit with your foot each time you get in or out of the car, on the top corner of the "A" piller trim, just below the dash line, and EASILY seen as you open the RH door (RHD), and I am guessing yours is on the LH side, but that is purely a guess. Remove that cover, it is just spring clipped intp place, raise the plunger, then repress it, that will "reset" the thing.

The fuel gauge is more than likely the float has just had a "moment", and that also "just happens" and it gets fuel inside it and sinks. The dash unit can get all fuzzy at times, but is generally reliable. The ACTUAL earth of that instrument binnacle is questionable, and I have added an extra earth wire to way too many cars over the years to correct odd ready gauges, and generally "dull" lamps. This has NOTHING to do with the "no go" of the V12 bit.

I would put my money on the module inside the amp as a starting point, and of less $$ than other items.

Agreed I inadvertently hit mine and it took me a couple of hours to work out why it would not start.

According to the ROM the inertia switch is still on the RH side of a LHD car. The switch is basically a fuel cut off, so the engine will turn over but refuse to fire.

Thanks Grant and Warrjon, I will try those things out over the weekend. I hope it works, the owners of the underground car park are going nuts at me! Its not the lightest of cars to try and tow out, ha ha.

Since the weekend is still approaching I have some other ideas, haha.

Find an old spark plug, ANY spark plug will do, and plug it into one of the plug leads, #2 & #3 are easy to get at, and rest it on a metal bit so it earths, and crank the engine, if you got spark, GOOD for now. If no spark, the module is #1 again.

After this cranking to test for spark, your system should have primed the fuel rail, SO.

Take 2 spanners (shifters we call them) and "crack" the fitting where the fuel line enters the fuel rail on the RH side, and observe the presensce or absence of fuel, TAKE CARE AS FUEL SPILLAGE WILL OCCUR, now, if there is a "squirt" of fuel as you crack that fitting it will be deemed you have fuel, and combined with spark, it SHOULD run. If you got a "dribble" you no got fuel supply/pressure and there in is your problem.

With the ignition ON (engine OFF), turn the throttle capstan fairly quickly (like it would if you launch from a traffic intersection) and you should hear all the injectors fire, much like a loud "clack", and this is just verifying that the ECU is triggering the injectors, nothing more.

Check the wiring at the CTS (coolant temp sensor), which is located on the top of and backside of the thermostat cover LH side, and has a plug on it just like the injectors and 2 wires. The wire INSIDE that plug are well known to fracture with old age and vibration, and if that sensor looses its connection to the ECU the engine will NOT start, period. Check up inside that boot, and the inside of the rear of that plug. I say this due to the sudden death of your engine, and I know that if you got a running engine and unplug that sucker the engine will stop dead.

If any more brainstorms come thundering in I will post them.

Enjoy

Warrjon- my LHD car has the inertia switch on the left side, right by my foot- so I can kick the plastic cover off at least once a week when getting out. :-)

Another error found in the Jaguar ROM to add to my list. Lucky the Brits did not make the Space Shuttle.

Thanks everyone for the advice, the Jaguar is purring again!! Infact it revs a lot smoother since the new ignition coil and amplifier are in?
You all saved me a lot of hassle and expense, huge thank you to all of you.

Just one more quick one though, I have knocked one of the wires off from the kick down switch by the throttle capstan. Can i just solder it back on? Its not a moving part at all is it?

SWEET, that is another Jag owner who can now go to France in style.

That switch is the fuel enrichment switch and the wires are usually attached with spade terminals. I would NOT solder to the spades of the switch diectly as you may melt the switch. Replace the spade terminal on the wire and slide it on the terminal of the switch. Those switches are very fragile, and old age does not help, so be careful.