Hate to introduce myself like this but, here is my issue. I just picked up an 08 XK with some 60K miles, not in bad shape but has been neglected the last year due to a convertible top issue which I will address later. My pressing issue is it was running great when I test drove earlier as well as today when I moved it and put on a trailer, now I get nothing when I press the start button, mind you it had to be jumped off every time to now due to a weak battery, but when I got it home it would not start with a boost or with a new battery. The only thing I did before i tried to start it is a new battery in key fob, which I need to source a new one of those is the current one has been neglected. In my opinion the fob is good as the screen is reminding me to remove the fob when I get out. Did I miss the paragraph on how to correctly hold my tongue while starting, my sequence is key fob in the center console dash screen tell me the top is unlocked, which it always has, tire pressure is low and I depress the start button. What am I missing? My prior British car experience is and MGA and an MGB, much more simplistic and I know these things are electrical current sensitive.
Thank you in advance,
Tim

 

Only advice i can give is to put car (battery) on charge over nite and try in morning take a reading from battery before and after charge

 

Although you don't say it when describing your starting sequence, assuming your foot is firmly on the brake. You can try pushing on the brake pedal both before and after pushing the start button.

 

foot on brake pedal? try pushing harder on the brake pedal?
is the car in park?
when you say "FOB in center console" are you putting the Key FOB in the center console port?
If the FOB is fully charged - get out lock and unlock and try it again.

 

Sounds like the battery is shot and even if you charge it , it won't be able to start the car. Get a new battery and charge it fully before installing it.

 

New battery fully charged has not made a difference, could I somehow have activated a security setting to prevent the car from starting? Letting it sit overnight with the battery disconnected, get back on it tomorrow.
Please keep the ideas coming, I will try everything tomorrow.

 

So it is a New battery . only other thing i can think of could be a brake servo issue

 

Upon reading my first post I realize I did not clearly state timeline of the batteries. Cranked with boost and loaded on trailer, got home and nothing, tried a booster here and no go, went to auto parts store swapped old battery for new prorated battery and bigger booster, still nothing. Tell me about the brake servo, what am I looking for, switch not closing so car thinks it is not ready to start?

 

When you say you ‘got nothing’, do you mean no electrical activity at all? No dash lights, no chimes, no infotainment display? If that’s the case, you’ve got electrical issues, maybe as simple as a dead battery, or not.
If you have dash lights, chimes, etc., try this:
1. foot off brake
2. press and hold starter button
3. stand on the brake pedal, really really hard.

 

I do have dash lights, just not cranking. Have searched he a lot this evening and others appear to have had same issue. I plan to try the foot off brake, push and hold start button, stand on brake first seems to have worked for others. Next is check everything in the start sequence, something could have jiggled loose.
Thank you to all and will post a follow up.

 

If you have dash lights thats a sign the battery ok starter motor and ignition coil are next so is fuel pump as it might not be getting gas . hope you get it running

 

if the brake has been pushed and no air in system try really pushing hard on brake and see if that does it if the dash lights up you should be able to start it

 

Update, this little exercise is done, I thank all, and I think all, told me to push real hard on the brake pedal, she lives again. I still have a few gremlins to chase out and, number one being a convertible top that will not retract and a warning of "top not latched" or something like that.
I do have another question, until I am confident in the car I am proceeding carefully and disconnect the battery when I am done with it as I have read much here about phantoms draining the battery. While I was disconnecting the negative lead I noticed something still running and did a little poking around, the navigation disk was whirring away, but naturally stopped with I cut the battery, anyone know how long that is supposed to keep running, I would have thought it stopped when the motor shut off, thinking that is an issue.
Again my thanks,
Tim

 

Happy ending . get a battery maintainer as these cars are notorious for electrical gremlins if battery is low

 

Everything shuts down in about 5 min. There’s a small fan next to the steering wheel on the dash behind a small grill that you can hear running. When that goes off is a good sign she’s shutdown. Locking the doors stops the car from searching for the key remote I lock it even in the garage also keep a battery tender on the battery if not being used for extended periods

 

That is true if you lock the car but if you don't it stays in convenience mode for around 20 minutes and things like the nav unit will whir away.

 

Thank very much, learning something new every day and I assume those are just cooling fans doing their respective jobs. I am thinking a battery disconnect switch for awhile, can’t drain a battery if there is no way for the juice to get out.

 

A brand new battery sitting on the retailer's shelf will slowly discharge even though it's not connected to anything.

Why do you need a battery disconnect switch? Just remove the negative battery cable from the terminal. Note that doing so may cause more harm than good. You may have to reset lots of things that have lost their memory and your transmission may have to relearn your driving style. And your alarm system, Smartkey and door locks won't work.

Buy a CTEK or other quality brand battery maintainer. I always keep both of my Jags on battery maintainers to keep them fully charged and have never had any electrical gremlins.

 

+1

 

One other thing - I know that it's the opposite of what the Owner's Handbook says, but trust me, I've been doing it for years and it works. Press the START button first, before you put your foot on the brake.

All you'll need is a light tap on the pedal, and it'll start right up. And remember to keep your foot off the brake pedal when the engine isn't running. Inadvertently pumping the brake pedal is what causes the high pedal that makes it difficult to start.