You bought a Jag. Suckered. Kidding. Kinda. Lol
Let me know if you need bumpers I have couple. If the wiring is fried then repair it and try old alt. No sense replacing parts if not needed.

 

There is a power post on the firewall on right side. That has constaint power to battery

 

Yeah the shorted wiring killed the alternator. I had it tested and it wasnt putting out any juice. I do need a new rear center plastic bumper cover and a right hand front one as well. PM me with a price and shipping quote?

 

Well today I have good news and bad news. Good news is, I solved the charging issue, and was able to take the car out for a drive. Bad news is, It died on me at a stoplight and wont start now. The starter just spins. Before it died, I felt a huge loss of power so Im wondering if my cap and rotor went, or if the starter is bad.

 

Try the fuel pump first.

 

Havent had much time to tinker on the xjs lately, been super busy with work.
Fuel pump is working fine and I have a fresh fuel filter on there. I also tried a little bit of starting fluid in the intake to see if it would fire and I'm not getting anything, so my ignition system is what died on me. It also sounded like I was getting a misfire in one of the cylinders shortly before it died, so it looks like I'm going to be replacing the entire ignition system which it looks like it has never been replaced..... hopefully I can my cap rotor wires and plugs installed this weekend and pray that I dont need new coils too!

 

DELETED double post

 

In my experience it is highly unlikely 2 coils or 2 ignitors failed simultaneously. It is more likely that the problem is in the harness, connectors or distributor. Check the distributor and rotor, if they are in good condition and genuine Marelli I would not replace them, the genuine Marelli are far better quality than the aftermarket items, I have both.

Also the ignition lead order on the Marelli cap is different from the Lucas so when you put the leads back make sure you follow the cylinder number on the cap or the Marelli ROM Supplement NOT the HE ROM.

 

Both coils and the cap and rotor are original Marelli parts, and don't look like they've been touched since they were installed at the factory. I will try to salvage them if I can.....

 

I repeat this all the time on here, so I'm sorry if I sound redundant. I can almost guarantee you it is one, if not both of the crank sensors.
Pull a plug wire, and see if it will arc to ground when you turn it over. You may be surprised to see it has fire. The problem most likely is a faulty signal. These things are 25+ years old. They are a service item.

 

Ill give that a try! If it is bad crank sensors, how difficult/expensive are those to replace?

 

I always forget about the crank sensors, I've never had a problem with mine.

Front is TDC sensor and rear is engine speed sensor.

Front crank sensor is under the crank damper on the front of the engine and the rear is on the flywheel. Both are easy to remove, the rear speed sensor is not adjustable.

Pull them out and check for debris especially metal on the sensor head, with oil/grease the head can pick up metal shavings/dust, this will effect the signal. Disconnect the plugs and clean the pins.

 

Looks nice, Nyan (just catching up with your post). I think I saw it on our local Craigslist (Detroit!) That paint looks like it should polish up really well!

I'm sure you'll sort it with the help of this forum - IMO the guys on here know absolutely everything re the XJS,

Well done!!

 

The problem is, they aren't sensors at all. They actually produce power. Over time, and heat, they fail because they are made with a magnet.
It is correct that they aren't adjustable. But I filed the mounting boss to move them closer in, to achieve a .020 air gap.
My 97 XJR had its front crank trigger go bad not too long ago.

 

If I bought a Marelli car I'd just replace the two sensors as a matter of course and be done with it.

Cheers
DD

 

I've only done the job once. I found it easy...BUT pay close attention to how the wiring is routed. I didn't, and it caused some difficulty as they're manufactured with no extra length in the wiring to accommodate...um....alternate routing schemes.

Cheers
DD

 

VR sensors are extremely reliable, they are a permanent magnet wrapped in a coil, very little to go wrong. My car still has the original VR's and has nearly 300,000km

I have seen the tip of the magnet broken from debris between the reluctor and sensor, this would reduce the signal level. Also the wiring and or connector.

 

The problem with a magnet, is that it weakens with heat. That is one reason a aircraft magneto is a regular service item. Not much to go wrong until the magnet weakens and it starts feeding the wrong signal to the ECU.
The rear "sensor" on the Marelli car starts sending about .6 volts AC to the ECU at cranking speed, but can go as high as 80 volts AC at full throttle. The front one is triggered by the three fingers on the damper, so it is nowhere near as high. But let it give the ECU a voltage outside the built in parameters, and the engine simply won't run.

 

The peak to peak voltage does not change to that extent, I know I have scoped it. the voltage output is determined by the number of turns on the coil not the number of teeth on the reluctor.

The ferrite magnets used in VR sensors have a Curie Temperature of around 300°C this is the point where the loss of magnetism is permanent, most have an operational temperature of 250°C, below this point once the magnet cools magnetism returns to normal.

 

Well I got the cap, rotor, wires and plugs replaced and Im going to try starting it tonight after the battery charges for a bit. I bought a crank sensor but im going to try it without the new sensor for now and go from there. The rotor and plugs looked pretty fried after I pulled them out so it might just be that. If she still doesnt fire, Ill do the crank sensors and coils next time I get home for a weekend.