If I've got to take out the fuel rail I'll just have the injectors professionally cleaned and flow tested.

When testing these injectors does it matter which pin gets the positive wire and which gets the negative?

 

Not a bad idea to just have them professionally checked out. Im not sure if it matters, someone more educated will have to answer that. I *think* the car I did it on didnt matter, but that was a much older car.

 

This method is actually not possible on the Jag injectors as they have "side feed":

 

So I tested the injectors tonight. It was actually much easier to get them on and off than I thought it would. Everything went smoothly except that I lost one clip for the fuel injector wiring connectors, it flew off when I was trying to remove it and I don't know where it landed. I'm worried it could have fallen into the valves but I searched through there pretty exhaustively with a magnet. I think it likely fell under the intake manifold. I'll search again for it tomorrow when I've got fresh eyes, but it looks like I'll probably need to get another one. Anyone know where I can get one of these? Is this an off the shelf part I can get fairly commonly?

Anyway onto the test results. I soldered small alligator clips on to some wires with a larger spring clamp connector on the other end to clip onto the battery terminals. I clipped the negative alligator clip to one of the injector pins, and then quickly touched the other alligator clip to the other pin. Listening through a mechanic stethoscope I could easily here the clicking on all eight injectors.

So I guess the good news is the knocking isn't from the injectors so I don't have to take half the engine apart to get them off.
The bad news is it wasn't injectors so now I'm left again not knowing what the problem might be.

 

The clip should not be removed in order to unplug the connector, it is just pressed-in. Otherwise, many 2-pin Bosch connectors use this type of clip (on Jaguar, BMW, Volvo, Mercedes etc.) not only for the injector connectors but also on the various sensors. You should be able to easily find it at a junk yard.

 

I wasn't trying to remove it, I had the clip raised on one side of the connector and when trying to get the other side up I flew out like it was spring loaded.
BobRoy is kind enough to save me a trip to the junk yard, he said he'll send me a few off his parts car. So thank you to BobRoy!
For those of you looking in the future the clip seems to be called Bosch EV1 style connector. I found a few connectors on ebay that came with the clips but they all seem to ship from china and take a month to arrive.

 

So tonight I finally got some time to work on this car again. I put the valve covers back on and I attempted to check the fuel pressure on the fuel rail. Unfortunately the fuel pressure tester I borrowed from Auto Zone did not appear to be working. I'll have to go get a loaner from another place and try again.
I'm hoping the fuel pressure test will tell me something about what going on, because if I don't get any information from this I'm at a loss as to what to trouble shoot next.

 

This kit from Harbor Freight is excellent value and will fit on the Shrader valve of your fuel rail.

Use the available 20% discount coupons and it is $17.15 out the door.

https://www.harborfreight.com/fuel-i...ter-62623.html

 

Thanks. That's basically the kit I used, I got it as a loaner tool from Auto Zone though.

 

Buy your own, then religiously follow the instructions.

 

So I got ahold of a working fuel pressure gauge, tested it and at idle it was 45psi, right where it should be.
I am now at a loss as to what to do next, the car seemingly has spark, has fuel, the timing is good, I have run out of ideas on where to troubleshoot next.

 

The fuel pressure at idle should be 38 psi. If you are reading 45 psi, the vacuum hose from the FPR to the port on the supercharger may be disconnected or it may be broken.

The port on the supercharger:

 

I'll check that, but I don't think that would cause a misfiring on one whole bank. It could also be that the head breather hose on the driver's side had to be disconnected to make room to attach the fuel pressure tester.

 

So I did one last attempt at trying to source a misfire, and that was to check for leaks on the "donut gaskets" on the supercharger My thinking being that is it one leaking from the driver's side one but not the other, the cylinders could not be getting enough air causing the misfire and explain why its only on one bank. First I tried spraying starter fluid around the gaskets to see if the rpm jumped, but no such luck, then for good measure I sprayed soapy water to see if there were any bubbles. Again nothing. At this point I feel like I've run out of things to troubleshoot, having no idea where to look next or what to try to solve this I had to admit defeat and give up. I idled the car out the garage and down the driveway and had it towed to a local Jag repair shop. Hopefully they can short out the issue, and hopefully it won't be too expensive.
Now I'm just waiting to hear back what they find.
I'll keep you all posted here.

 

So I finally have some good news to report! The shop I sent the car to has diagnosed the problem, its seems the wiring harness for that bank of the engine had come partially unclipped, that would explain the intermittent misfire as the engine would shake the connection loose and the connect again, why it was sometimes on two cylinders, sometimes on four, but at least its an easy fix. I haven't got the car back yet as I'm having the shop take care of a few other things, such as the trans overheating issue, which probably is the control module for the transmission, as well as replacing the inner tie rod. Anyway, she will soon be back on the road!
Honestly I'm actually starting to get happy about this car again, as a backyard mechanic I'm fairly experienced, I've always down my own maintenance on my cars, from oil changes to engine swaps. I've even done driveway transmission swaps with nothing but jack stands and floor jacks.
But this car, this was one was a slug of a job, constantly running into set backs, oh and then some of the location of many of the nuts and bolts that left me wondering if these engines were even designed with servicing in mind at all. This plus the a work schedule that often meant I was only working on the car on free weekends, often having to stop when I realized I needed to order a new part or gasket to continue, and wait for it to arrive and for another free weekend until I could continue on it. I resented that it was taking up space in my garage (and forcing me to work on my other cars in the driveway) and I was starting to loath working on it. I was begining to hate this car and wondered if I'd even be able to enjoy driving it if I did get it up and running. But for all the frustration, I'm actually starting to get excited about getting this car back and driving it again.
It took me three years, but admittedly most of that time was spend with nothing happening on the car while I went back and forth on whether it was worth fixing it (in hind sight from a purely financial perspective, I probably should have cut my losses. I don't think it wasn't worth putting this much money into a car worth only a few thousand in running condition), but I'm glad I did because I learned a lot from taking apart and putting back together this car, and would be much more confident tackling a job like this agin.
I'll post some pics when I get her back, and while she might not be the finest example of an XJR, I'm feeling motivated again in ym original plan when I bought the car, to bring it closer to that.

 

Glad to hear! It lives!

 

Thought I'd give an update for anyone interested. The car is back from the shop. I've got a few little things to fix, like a leaking valve cover gasket, I guess it needs new gaskets from pulling the valve covers on and off trying to figure out the misfiring, also need to get new tyres and an alignment, them more creature comfort things such as install a new stereo with bluetooth and replace the antenna motor. But before I can do all that I have to get it to pass California smog in order to register it. I'm stuck at this point because I can't get these damn readiness monitors to clear. I've put over 300 miles on the car with no luck, I've tried completing a few of the drive cycles I've seen people post in other threads, but I've read multiple different instruction of what to do and I'm also finding it difficult to find conditions in order to complete them. Stop lights, traffic keep spoiling my attempts.

 

Is it throwing any codes or does it just not want to complete its computer checks?

I had a car that took a solid 200mi before it would complete all of its checks, had to do several cold starts, hot starts, a certain amount of miles at higher speed and a certain amount in stop/go traffic.
It was almost like a game when I had to get some things fixed for it to pass inspection. But it did complete it, ive heard cold starts are usually part of the catch.

 

No, not throwing any codes, but I've now got bigger problems. I was careless and left the battery tie down unbolted and lose, it shorted over the positive terminal and the chasis. Complete electrical shutdown of the car, had to tow it home. I'll start sorting things out in the morning but I have no idea what I'm in store for.

 

I hope things come out more simple than they seem! Electrical...faults... are where I start getting annoyed with a car, BUT may not be costly to fix. Just time consuming.