Yes or No question: Are the injectors clicking when you crank?
If No, 99.99% likely this is related to CP or Engine speed signal or their related wiring. As Steve has stated. Next steps:
Access the Marelli computer behind the right side footwell kickpanel.
Check the CP and ES sensor inputs at the Marelli computer. They should be same as what you saw at the sensor plugs. If both good, check the Marelli computer output to the Lucas ECU in the boot.
If good, go check the Marelli computer input at the Lucas ECU to make sure the wiring is ok between the two.
FWIW my Marelli car was always anemic when cranking, even with a topped up battery. But it would start. A gear reduction starter makes it crank way better. I don’t think the starter is your problem.
If got a spark it should start . Not necessary so on easy Start spray. If more than four or five injectors are blocked it will not start and if the car hasn’t turned over for a long time they may have seized.
Also check the fuel pressure to the rail if the fuel pressure is too low it won’t start.
Also there is two wires which you connect to the main battery if disconnected or rested it won’t start
Hi. Worked on the XJ-S again today. Yes, the injectors click when I crank. Both CPS and ES sensor are working as should. The problem I’m having is that the starter sounds like it can’t overcome the engine detonation and bogs heavily. Please see my attached video. Either it’s a bad starter that is robbing the injector and ignition system of necessary voltage or the timing is off and early ignition is straining the starter.
Voltage drops from 12.5v to 8.7-9.5v when I crank. All the interior lights dim and flicker when the starter bogs down. I’m ready to pull the starter and have it checked. Any ideas??
Thanks,
Mark
@sbobev what about distributor alignment? It should never be be messed with but if the PO did…? I think u have an album that shows how to check iirc.
Correct. All covered here and in many other topics in the archives:
Hi. I got it figured out. I went to check the timing and as I was about to remove the distributor cap, I thought I’d double-check the coil wiring. Someone had crossed the A and B coil leads to the cap!
The engine sounded completely different as I try to start it of course. The lights did not Flicker and after several revolutions the engine sprang to life. The car sounds fantastic. It has a performance exhaust system special intake and AJ 6 super enhanced computer. I took a video of the car running. Now I have a different problem. What I thought was a sticking oil pressure gauge turns out to be low oil pressure. I drove the car around the block and after I put some heat into the engine the red oil light came on. I am going to hook up an oil pressure gauge at the sensor and see what’s going on. I am afraid of the worst.
Congrats Mark! That’s great!
Good call on putting on a gage. Would be weird for the gage and idiot light sensors to both fail. But you never know. There should be an unused port on the left side of the “tree” that you could use… but it might be British pipe thread.
Assume you’ve changed and refilled the oil. I prefer 20w50 here in Az but of course there are a million opinions.
FYI, later revisions of the oil pressure sensor turned it into another idiot light. Complaints about the variability of the indicated oil pressure - it’s certainly not like other cars I’ve driven - caused Jaguar to change the progressive sensor to be an on/off pressure switch, plus a resistor, to give half reading on the gauge.
Hi all,
I removed the low oil pressure oil sending unit on the tree and screwed in a mechanical oil pressure gauge. Much to my surprise, the pressure went right up to 70 psi at cold start and leveled out at around 45 at hot idle. I will leave the gauge attached and go for a ride tomorrow.
I am relieved to see those numbers to say the least.
MP
Wow- great news Mark!
On a Jaguar, when a gauge warns of trouble, suspect the gauge.
Yep, about what mine does…75 idling cold, 30 idling warm, 50 driving. So nice having accurate gauges for this car (I have one oil gauge and two temp gauges in addition to barrel gauges)
My oil sender for the barrel gauge was leaking, replaced it with new, and it still reads a good 30% below what the aftermarket gauge reads.
The barrel gauge is in excellent condition, BTW.
So far so good with the exception of an issue that keeps popping up after a 10 minute drive. During hard acceleration after the engine is up to temp, I experience a misfire and then the engine slowly loses power to a point where it just dies. It’s as though the fuel filter is clogged and it starves for fuel but after a few minutes, things are back to normal.
I would like to get some opinions before I start troubleshooting.
Any advice would be appreciated.
Thanks,
Mark
Sounds like the classic “clogged screen in fuel sump tank.” Lots of threads on this forum, as well as in the Book. That’s my guess, worth what u paid for it. 
Mark,
That sounds like a loose connector or wire problem. Get the engine all warmed up, and with the engine running open the hood and start wiggling the engine bay wires until you can get the engine to stumble.
Another possibility is an ignition switch problem. Again with the engine warmed up and running try wiggling the ignition switch wires beneath the dash.
Paul
Mark,
I just read what Bob wrote and I agree with him that debris in your fuel tank is very likely clogging up your fuel delivery system.
I experienced a similar engine cut out problem in one of my XJ6s years ago that I assumed was ignition and not fuel delivery related. The engine would stumble and die after warming up nicely and then restart shortly afterwards only to die again. To sort out conclusively whether it was fuel or ignition related I connected my fuel pressure gauge with a long length of hose to the fuel rail so I could observe the fuel pressure as I drove around my neighborhood. Sure enough after a short drive I watched as the fuel pressure dropped from about 36 PSI and then the engine stumbled until it died around 15 PSI or so. I had debris in the fuel tanks that clogged up the fuel strainers. The same thing is possible in the XJ-S with debris in the sump tank clogging up the strainer and fuel filter.
As Bob correctly points out this is a common problem especially with cars that have sat for a while. There are lots of posts about this in the archives
Paul
You guys are the best. Thanks. I will check it out.
MP
To rehash a bit: The known problem here is that rust particles and other garbage in the surge tank gradually collects on the pickup screen as the car is running and plugs it up. When the car is shut off, the crud falls back to the bottom of the surge tank, so if you take the pickup out it may actually look clean! Next time you start it up, the crud gradually plugs up the pickup again. Very, very difficult to get that junk outta the tank.
Jaguar’s fix was a replacement pickup screen, twice as large and therefore twice as difficult to plug up. In theory this might make it impossible to plug up; it could get completely covered with junk and still be able to pull enough fuel through to run the car.
My fix is different. Remove the pickup tube, take the pickup screen off the end, and heave it over the fence. Reinstall pickup tube without it. Then install a 1/2" inline fuel filter between the pickup tube and the pump inlet – a bit problematic because they’re so close. I actually installed about 3 feet of hose and made a big loop around under the battery tray so the filter could be installed without pinching a hose. From then on, whenever crud plugs up the fuel system, you take that inline filter out and throw it over the fence, and it takes all that crud with it. Install a new clean filter and you’re good to go.
Gosh, they sure look good in black. Beautiful car!