Hi all, I'm trying to nurse this 1995 3.2L automatic XJ6 I've 'inherited' into working order again, but I'm a total noob to Jaguars, and non-working cars in general -_-"

It has been working recently (3-4 months ago, when it was being used routinely by the previous owner) but often had problems starting: starter would spin and spin and spin, only starting the engine after many tries; but then it would run quite fine (as far as I could tell).
The starter would sometimes not run at all with the key, requiring the use of a 'bypass button' (that I imagine directly powers the starter relay) that has been fitted to the car (supposedly this 'no starter' is not an uncommon problem, or so I was told by the previous owner)
The difficulty starting was thought by the owner to be due to a problem with fuel arriving to the engine, although that may well have been complete speculation.



The car has been mostly standing outside for the last months, I just started it a couple of times (with difficulty), but now I cannot get it to start at all:
Last week I started looking into it, and after many tries (waiting a while each time to let things cool off just in case), the engine would fire for a few turns, but would then die.
I needed to use the bypass for several of these attempts.

The poor thing was low on gas (dial in the red, but no "critical" lamp) and the battery was pretty much dead (especially after so many attempts...), so I got some fuel (a 6L or so jerrycan) and removed the battery to charge it (there was no electrical outlet close enough to the car)

Now the battery is full, but I can't get the starter to even try to spin the engine with the key, although the bypass still works (but still fails to start the engine)

When I turn the key to position 2, there is a series of 10 beeps from the central console (I think these are coming from the AC unit, that displays 'Er' during the beeps; this seems corroborated by the driver manual.)


I'm rather savvy with electronics and mechanics in general, but have next to no experience in troubleshooting cars, so I'm at a bit of a loss as to where to even start...



UPDATE after cleaning/washing the car in and out in today's relatively nice weather (compared to lots of rain recently):

I managed to get the car to start a few times by using the bypass, but it's far more reluctant now that night has fallen (something damp/temperature related?)
Idle sounded OK, seemed rather high to me (1700rpm) but gradually slowed down (700rpm) [Automatic compensation for temperature as the engine warmed up I guess?]

This evening, It started, but then stopped dead after a few moments, while I still had my foot on the gas.

Now that it won't start, here's the latest status, engine off:
'Check Engine' light on most of the time.
'Battery' light on (normal AFAIK)
'Oil pressure' light on (ditto)

When the engine starts, all lights go out.

When the engine dies, Check Engine comes back on (battery and oil may too, didn't check)
However, check engine seems to blink randomly at times, and the RPM dial jumps around near Zero (possibly faulty engine position/speed/?? sensor?)
While this jumping around is going on, I can hear some things moving around in the engine compartment (can't tell what), and a knocking sound from the boot.


UPDATE 2:
Managed to get it to start again after fiddling with all the connectors I could get to under the bonnet... The Check Engine light still comes on though.
Noticed the Check Engine blinking, RPM dial jumping and noises also happen when just leaving the key in the ignition for a while.
Investigated the knocking, turns out it's the "SRO 18.30.70 / Fuel Pump Single" relay (According to the Vehicle Service Manual found in another thread here)

Any clues on what to start checking welcome!
I have a decent multimeter so I can check things that need one.

Cheers,
Jonathan