New to site. Looks really good.
My wife's XK8 will not crank. Off and on the last few months the key would not turn and sometimes crazy stuff would scroll on the dash. eould take Negative Battery Cable off or let sit and would start.

Couple weeks ago she got the green shower. Ordered hoses and replaced. Was very difficult but we got it. I think the lock is messed up because you have to latch it totally with the hex wrench, but it works. May even have damaged the hydraulic cylinders as it doesn't go down all the way and the back windows don't respond. Put a switch to raise/lowere ack windows as displayed in YouTube and it works.

Was ready to drive and won't crank. I've read and tried so much it's about yo drive me nuts. Battery was low. Tried jumping the car. No start. Tried a different battery no start. Can not shift from park with removing hex key and pushing something in hole. No start in neutral either.
Found start relay. Jumpered across terminals and car cranks but no start, even if someone tries to start with the key the same time I make it crank. With key on have 12 volts power to one side of the coil on the relay. From reading I assume the Body Processer Module grounds the other side of the relay coil to crank the car. While cranking I read a positive voltage on this wire instead of ground. I was thinking maybe the neutral safety switch may be the culprit, or possibly the Body Processer Module doesn't have power. I've read of another fuse box under the passenger rear seat (Heelboard) that feeds power. Is it on this model? Am I going in the right direction? I have no prints, except what I find online. It's very frustrating. Please help.

 

Check and see if your visor mirror lights are working.

 

Do you have a second set of keys? I would get a brand new battery (not a different one, brand new) and do a hard reset to get things at a baseline.

 

This might help

Link JagRepair.com - Jaguar Repair Information Resource

 

2 sets of keys. Both same result. Turns but no crank.
What is a hard reset?
Will not be able to check until morning. I'm at work trying to gain info.
Is there a fuse box under seat on this model? I looked around before work but was rushed.

 

Gus that link is great. Prints are difficult to read on the phone. Need to print them out.

I don't see a fuse box under the rear seat. So where is the Body Processer Module fed from? I would like to check it first. Never had a problem shifting from park before and best I can tell the solenoid that allows this is fed from that module. And the module grounds the start relay. If power is present I may try accessing and grounding the wire back to the module from the Neutral safety switch. I guess it's also possible the ignition switch start is not communicating with the module?

 

I know of no fuse boxes behind the seat. You need to look at the wiring diagram for your car and it will show you where they all are. Now back to my question on the visor mirror light is it working? If it is not check the drivers side fuse box that fuse will prevent you from starting the car!! My guess is that when you replaced the hoses to the latch you shorted it out. Reason #1 to disconnect the battery when you work on the car.

 

When you get a battery in try a hard reset .try to start . If you can scan the car. And see if it throwes any codes. With out reading the codes you are shoting in the dark. Good luck .and please post any codes.

 

May or may not be relevent but had similar happen in my 2000 xkr, although it is a coupe. While doing roof console work reading voltages at plug I had shorted two pins blowing fuse in drivers side interior fuse box that feeds glass break sensor (I can't remember the number) Car would not crank and when starter was jumped would not fire.
Might be worth checking your drivers side fuses.

 

I checked every fuse I can find. All checked good except 4th one up on right of fuse box on dash panel drivers side. I checked it with VOM and it pulled approximately 24 amps.

 

WAIT. My son and daughter had the EXACT same issue, I just remembered. If my daughter would slam the trunk it would work again. We sanded the contacts and replaced the negative cable and she hasn't had a problem since. I have had some issues with the braided negative cables, so I switched to sheathed.

 

What did slamming the trunk do? Surely you can start the car with the trunk open?

Fuse that keeps blowing looks like #15 (5 amp) in drivers side fusebox on side of dash. Trying to figure out what it feeds.

 

I think it boiled down to the negative cable corroding and slamming the trunk did something? I cant say why I just know that is what worked.... A hard reset is taking the negative cable end and touching it to the positive post/cable for 20 seconds or so. Apparently it drains the electronics and creates a "reset" situation. Don't discount the importance of a clean, good negative connection.

 

I can't figure out these fuse numbers. What number fuse is 4th from the bottom on the right column? There are two columns with 9 in each column. Its the one I'm pointing at if the picture shows up.

 

I think that is the one gave me those symptoms. Could the harness have been compromised somehow when roof problem occured.

 

I just googled xk8 fuse layout images and found a confusing variation in fuse values in the various positions in that fuse box. It is possible I suppose that an incorrect value has been installed in that spot. (The book says #6 @5AMPS and #15 @25AMPS. Side by side, but your pic has them swapped, is it possible these have been transposed?)
I also noticed that the security module takes a feed from the latching mechanism/switch so the problem you have with that not latching correctly may be the reason for your no crank as that security module needs to OK the crank/start command from the ECU. One of those fuses also supplies the key transponder and top header console ( #6 -5 amp i think)

Edit. Disregard my comment re. swapped fuse positions, just checked my own. I think they must number from top right hand down.

 

Exactly what I thought. You would think fuses would be numbered left to right starting in top left, this would make that fuse #15 which controls ECM power. I was kinda excited that may be it.

But the fuse values line up more as if numbers start top right and go to the left. This would make it #6. Can't find what that does. I am tempted to put a 25 amp in there and try it.

I put the top down. No start. Maybe I should raise it back up and turn that fluid release handle on the hydraulic pump and latch it by hand again? I did notice the lock wasn't staying in the locked position, it was bleeding off. Can I jump it? What about the limit switches on the hydraulic cylinders? Will they hold you out. If the car doesn't know if the top is up or down will it start?

 

Don't do that, could end badly.
#6 feeds centre console switches, key transponder module, convertible top header console and rain sensing. If your car is fitted with glass breakage sensor it is also powered through that fuse (l think)
I can't help but think there is connection between your work on the roof latching etc. and your current problem, most likely security system/ transponder power issue.

 

The fuse chart is in the owner's manual (and frustratingly missing from the electrical manual). Check the stickies for a link to an electronic copy.

When I was chasing down some gremlin with my HVAC, I ended up messing with the fuses, too. I found the documentation accurate, but somewhat confusing as the column layout in the manual is made for page editing purposes, and does not reflect the physical layout of the box. I got my bearings by checking the fuse rating. I also figured out the fuse covered with the yellow plastic tab is for the airbag. I assume the yellow tab is a subliminal message that suggests it is not to be messed with.

 

Well it started.
Charged battery overnight. No start.
Played around with #6 fuse that was blowing. Jerked around on wires, hydraulic cables, etc and couldn't find a problem. Put new 5A fuse in and didn't blow. Didn't start either.

I hadn't totally reassembled the car after the green shower. I wanted her to drive it and maybe play with the latch some more to make it better and see if hoses are good. This was probably a mistake.

I checked voltage to plugs for visors and it was 12 volts. Just because Gus said to I went and got the visors and plugged them in. I saw the up light console by the mirror. Plugged it in and car started right up. (It has a module in it too that I now see. I thought it was just lights).

Just for the heck of it I unplugged the console and car still started. I have no idea. But it runs. Thanks for all your help. You guys are great.