Read your post and thinking

100 - 200 revs on starter is low , may be a true value or CKPS error , more like 300 , good battery ?

This starter rev may be too low for the CKPS as a turning engine for your follow - up fuel pump enable and empty / exhaust your 3 second fuel rail charge ( pressure related ) this is different than priming just the cylinders

But XJREngineer on the original Jaguar X300 engine design team says that 100 -200 is good

There are no foot peddle tricks beside one for bore wash correction

Never install battery in backwards , positive post fwd

Never over tighten the positive battery post bolt , splits special curved nut underneith

The X300 engine ECU is not programable like other later cars in that sense of the word but " oriented " to the TPS if not a close match on swapping parts

Fuel pump run ?

You can check the fuel pump relay small blade / slot socket Z for a ground provided by a so much live engine ECU

Parts can still be obtained as new for ECU and wire side connector halves

Econoseal 3 series as in this pic , TE Connectivity brand / manufacturer

There are 2 fuses A and B for the high power 2nd power to the ECU by way of the ECU controlled relay that is controlled by the ECU and brings power back into ECU , 1/2 your engine sensors , and your fuel injectors

A stored X300 can be in a bore wash condition limiting your compression for successful light off and carry on foward

The easy correction is holding the pedal to the floor and cranking , the ECU knows to not add fuel and the oil seal will be reestablished from under the piston , after reestablishment release pedal for normal start

I think I'm done editing , ask questions

Watch for how much your starter voltage sags on starter rotation

 

1. Make sure you dry out the ECU. Clean the contacts with some electrical contact cleaner. You might want to get a security torx bit to open the case up?

2. Replace the crankshaft position sensor. If you're not seeing the tachometer needle move, that is the likely culprit. Start there. It's a cheap part that you can replace yourself.

 

The CKPS is a generic part found at the common auto parts store , some keep a spare in the trunk so if it doesn't resolve you can keep it as the spare , there is no adjustment to installing CKPS , a good CKPS reads 1300 ohms as a basic meter reading , you can wipe clean the face of the sensor of grime that interferes with the signal , this is different than CKPS connector clean

The engine ECU will come apart with common torx bits that I'm aware of , make sure you reinstall the external case ground strap , notice how easy it would be to replace ECU side connector

The water that runs down into the ECU connector runs past rubber seals on the wires , so slight tug on wire as corrosion can be on the wire crimp to socket , there may be spare unused sockets , see socket map post # 46 , see the orange wire seals at the bottom of this link , the ECU side called header in this case is in the lower right side of page

This vender is in England I assume but you can use their part #s for US venders , red color is an issue to find

TE Connectivity Econoseal III 070 Female 36 Way Hsg Black - automotiveconnectors.com

Red color wire side connector TE Connectivity # 344111-5

36 pole female Econoseal connector 344111-5

 

large # 5 right ECU controlled relay ( 2nd power inside ECU ) fuses # 6 / 5 amp ( relay control ) and # 11 / 20 amp ( power pass through to be inside ECU ) both right engine bay fuse box , these 2 fuses are hot at all times , not dependent on king relay closing in the corner of fuse box

You can see this as a good fuse fuse # 11 at socket 3 of the ECU controlled relay socket base

Fuse # 6 at socket 2

The engine valve cover is not a good test meter ground