RESOLVED. THANKS TO ALL WHO GAVE THEIR INPUT.
car wont start and i just cheked for voltage on the cam sensor, crank sensor and mass air flow meter. im not getting any voltage. just 0.60 on the voltage cable with the key to ON position. im thinking there is a common supply for all this sensors and thats where the problem is. but i dont have the diagram. i swapped some relays around behind the right hand headlamp and fuse box. all fuses relative to the fuel injection system are operational also and all get 12 volt. cant make this jag start!!.

 

The ign volts for the CAS sensor comes from the relay INSIDE the RH fuse block under the bonnet. There is only one relay (blue) in there. It is called an ignition relay, and is one of many on the car.

On the side of that fuse block is a rubber cover thingy, under that is a battery cable, it is HOT at all times the battery is connected. See if you got battery volts at that connection.

Failing that I reckon the security system has had a hissy, and blocking ign supply for some reason only known to it.

I would disconnect the battery and let it rest while you have a nice alcoholic beverage, and then reconnect and see if all has reset itself, it does happen, been there.

 

yea there is power to that battery cable besides the fuse box on the right hand side. i have swapped some relays around since they are the same but nothing. im not getting power on the cam sensor and neither on the mass Air flow meter. might not be getting power to other stuff but those are the ones i cheked. the security system on the car has not worked for a very long time. the center lock button and the key fob has not worked since forever.
i even gave power manually to the cam sensor but that didnt help.

also that relay on the right hand side fusebox had a funky burnt smell but the problem was not resolved by swapping it can you give me more info on what other things this relay powers? im thinking the problem is around that area. either the relay isnt getting a signal to close the circuit or something else.

 

OK, got my page open, and I note that behind the RH headlamp there are 5 relays. Relay #5 (closest to the wing in the bank of 3) is labeled as "engine management system AJ16".

In the LH heal board section is an ignition relay #8, which is the one in with the fuses (as in the engine bay arrangement), as apposed to all the seperate relays.

In the RH heal board, SAME, relay #8 is labeled "ignition relay". Same location, in with the fuses.

In the RH under bonnet fuse block fuse #6 (Tan) is for the "engine management system control module".

Same fuse block, #10 (Tan) is "Ignition control, low current", whatever that means.

Same fuse block, fuse #11 (Yellow), engine management relay supply/fuel injectors.

Same fuse block, fuse #12 (Red), Engine management system/coil sensing, etc AJ16.

In the boot (trunk) fuse block #4 (Red). Security system.

Same block, #5 (Red). Body processor module.

Thats about all I can find relating to the ignition items that may be stopping this from starting.

I am assuming it is cranking, just NOT firing???????.

 

yep, endless cranking. thanks for the info ill check those relays.

 

Im at the car right now and swapped all those relays u mentioned but still no go :/

 

this could be a bad ECM. any way to be certain before removing it and taking it to a place to chek.

 

Mmmmm, I doubt the ECM, but thats just me. I have had NONE fail in all my years with them. My own 6CU on the Beast went flaky on the fuel pump control circuit (WELL documented), car still worked fine with a bypass in place, so a 16CU took its place looooong ago.

Have you now got battery volts to the CAS, Camsensor etc as you stated you did not at first????.

If that CAS is still getting NO power in the Red wire, that would be the first thing that needs fixing, and that has ZIP to do with the ECM, it plain and simply comes from that relay in the RH fuse block.

I also note that you said that the security system has not worked for some time, and I am just thinking that maybe it has decided to do what it should (come partially alive), and that is to prevent "starting". but allow "cranking"???.

 

you got me thinking about the security system. but its a long shot to go that route. yes the power to the cam sensor comes from the relay but the ECM is what sends the signal to the relay to toggle it. i have not cheked power again to the cam sensor. but i did try giving it some voltage directly(bypass) if you may. and it still wouldnt start. my cam sensor has 3 wires. in order from left to right (black and green , brown and green and blue) according to the snapon meter/computer i was using, the black and green should carry 12volt. but when i cheked that didnt have any voltage instead the green and blue had 0.60 volts and the brown is signal.

 

OK.

I still think there is something blocking the ignition power, and that security module just springs to mind.

Just for giggle, have you "reset" the inertia switch. Not sure what it cuts off on the X300, but the earlier cars was the fuel pump circuit only, but maybe it cuts more on these. I have heard of people simply resetting them and the car runs, but I am unsure of the original issue.

I have NO experience with the wiring of the ECM on these, as mine works faultlessly, so I have not had to dig into it to sort some gremlin.

I have read over the last couple of years of issues with a "growth" in the ECM sockets where the plugs attach, so maybe it has a growth and is blocking the signal????.

 

Yes yesturday just to be sure i pressed the inertia switch. but on the x300 when the inertia switch toggles the car wont even crank. There was a few harness plug terminals behind the right side headlamp with corrosion but i got those cleaned up real nice a couple of days ago. some guy told me that if the chek engine light comes on when i put the key to ignition then the ECM is getting power. im not so sure about this anyways i will verify that there is power to the ecm. The check engine light comes on for a few seconds when i switch to on and then turns off. I was going to work a bit more on the car today but the battery drained from so much cranking after trying something. im quickly loosing faith and thinking this will end up costing me a lot. so far this car has been a pleasure with only maintenance costs and no mayor repairs. and it still hasnt reached 100k miles. its at 98k. how to diagnose the security system? The key fob doesnt respond. the master lock button doesnt do anything, the alarm doesnt do anything either. The program keyfob procedure doesnt work either. the way i open the car is with key and to lock unluck all doors is by locking/unlocking my door.

 

Taking it to the jag dealer is out of the question. they wanted to charge me 400 for a powersteering hose alone, that ended up costing me 85 installed somewhere else.

 

well massive resuscitation of old thread. i have left the jag sitting all this time after replacing the crank sensor and having no success in it starting. i will start to work on it again this week and wanted to ask here again for more input and recommendations... i miss the jag.

 

Don't give up on it just yet! See my post about the VDP intermittent start. I just solved the problem. It took me 3 months to get to the bottom of that issue, and it turned out to be something really simple! I find that as time passes, I come up with more ideas about what to check and to test next. It's hard to let it go some days, but in time you will most likely succeed! I don't like the feeling of that problem that keeps the car from being "reliable".

As for the key fob/alarm issue, it all starts with the trunk. By that, I mean the trunk lights must work properly before the alarm can work properly. The lights are controlled by a small switch on the trunk latch. The wires at the right trunk hinge must be in good shape and not damaged or broken. Start there!

I understand via the service manuals, that the USA spec cars don't have a fuel cut-off immobiliser as part of the security system. Try to find out if you have a USA car........

 

thanks sleek for that boost in hope. i cheked and trunk lights work. and no visible damage to the harness runing on the right trunk hinge. the car is US spec. the keyfob hasnt worked for a very long time, the central lock either, the trunk only opens with key, all locks lock and unlock with key in door or by locking/unlocking driver door. the procedure to reprogram keyfob doesnt work so i always asumed the alarm system was dead. but this never caused an issue other than the inconveniences above.

the problem began over night and i could say it was intermitent for a while. cause the engine started a few days after it initially wouldnt start. it ran with missfire, later ran normal, later while testing for spark it ran again with missfire and after that never ran again. not the same day this was weeks in between.

wiring diagrams for all ignition system would be very helpful. so i can follow each wire testing continuity to begin with.

 

i think i just found the problem!!!! wow the black plug on the ECM. took a pic. on the pic the red plug is on the right side. must have the sunroof water passages blocked. and water dripped into the ECM. there is even a broken leg there. can anyone tell me by the leg that is broken what that connection is ment to do? anyways this has got to be the issue i mean WOW.

 

lukly internals of the ECM look clean. gonna try a bypass. of the broken leg

 

Yes!!! Its alive!!! Bypass worked

 

Damn that is some SERIOUS fungus growing.

Glad I dont have a sunroof.

Good news on the ALIVE Jag, sweet feeling.

 

Holy Crud!!

That was a nasty find! And you nailed that suggestion Grant! Congratulations avi, feels great to succeed after such a long ordeal, right?

Any change with the alarm/locking situation?

It doesn't rain much here, but I'm going to go check my ECU connectors now.