My XJR has been sitting in the garage for two weeks with the battery disconnected while I'm working on changing my timing chain tensioners. I have to do this a little at a time, when I have the time. I think I can finish the job this weekend.

Can sitting for this long with the negative terminal off the battery hurt the electronics in the car? Is there anything I should do (like a hard reset) when I hook it back up?

Any info appreciated.
Vector

 

Have your keyfob handy.

When you reconnect the battery the security beeper might start chirping as a warning that the alarm is about to go full on. Hit the unlock button and the chirp will go away.

The hard reset will have been done simply by sitting disconnected for the two weeks.

You may find it wise to crank the car with the fuel injection fuse disconnected so that you can circulate some oil. It is fuse #5 in the smaller fuse box in the engine compartment. 10 amp fuse in the middle position of the 9 in the front row of the box.

That cranking may discharge the battery enough to make it a hard start. So, you want to fully charge the battery before reconnecting. Might as well put the trickle charger on it tonight.

 

Mine was off the battery for almost 2 years. I did pull the fuel injection relay and the fuel pump relay and turned it over a couple times to get the oil circulated. The other thing i would recommend cycling the windows up and down. You should hold the button a couple of seconds after its all the way down and you will hear a little click and then again all the way up closed and listen for the click. I think this procedure is in a tsb somewhere.

 

Sean did you misread? The car was down for TWO WEEKS for gosh sakes. Hook the battery up and crank the car. Where is the drama?

 

What drama? Did a message get deleted?

Anyways, cranking with fuel disabled to prime the oil galleries is recommended by almost anyone who has had the top apart for a tensioner change.

 

New Jaguars sit on a ship for at least a few weeks with the battery isolator to disconnect the battery from the factory. I doubt several weeks or years will affect the electronics of the car.

When the battery is reconnected it is advised that a firm/clean connection is made without alot of sparking.

Here is a TSB for advise.

bob gauff

 

Sean:
Gotcha- I was looking at the specific question litterally- which was what effect having the battery off for two weeks had on the car's electronics. I would say a tensioner change alone would have minimal effect on the oil galleries, but I agree it is a good idea to prime the lube systen after engine work.

 

The reason for the emphasis on fully charging the battery is because of the preceding advice on cranking to prime the oil passages. If the battery gets weak enough during that phase, when the real start attempt is made the engine may not start even though it is cranking well. This is due to the ECM getting alzheimer's from having marginal voltage.

Didn't want the OP to tear his hair out on that one.

And then there is the alarm chirp thing. Very unnerving at 3AM when sneaking in some work in a prohibited area.

BTW, Sean is somebody else.

 

Sorry plums, operator head space!

 

S'all right. It's all good

 

I finished the tensioners tonight.

Hooked the battery back up, pulled the two fuel pump relays and the fuel injector fuse. Turned her over a couple of times, reinstalled the fuse and relays and she fired right up!

No drama at all! The clock was right and the radio presets stayed.

Vector

 

For anyone stumbling along later:

Once the fuse is pulled there is no need to pull the relays.

The difference between the two is that by pulling the fuse, the engine will not even cough because the injectors will not open. If only the pump relays are pulled, the engine will fire briefly before dying due to residual fuel in the fuel rails.

Also note that the fuse identification given is specifically for X308 systems.

 

To summarize in plain English, when you leave the car a while with the battery disconnected and then return to it:

1. Open the doors & trunk with the key (since the remote-fob won't work, lol) and pop the hood (aka. bonnet)
2. Remove fuse #5 in the smaller fuse box in the engine compartment. It is a 10 amp fuse in the middle position of the 9 fuses in the front row of the box.
3. Reconnect the battery
3a. if you hear chirping and there are no birds around, press the keyfob or turn the key counter-clockwise in the door
4. Turn and hold the key in the ACC/start (final-position) of the ignition for a 3-4 seconds
5. Remove the key from the ignition
6. Replace fuse #5
7. Start the car normally

Is that correct?

 

Just read the "battery disconnect warning.pdf" and have two questions:
- is it a problem if I had only disconnect the positive cable (negative is still attached)? I am currently traveling and the car has been sitting in a temperature-controlled garage for some months like that - the battery is new, only purchased a few days prior to my travel.

- the expedited ECM adaptation procedure seems to say to hold a foot on the brakes at the same time as giving it gas while the transmission is in drive-position - doesn't that damage something?! I have never in my life tried accelerating a car with my foot on the brakes, lol...

 

The preferred method of disconnecting the battery is to remove the NEGATIVE or EARTH cable first and reconnect it LAST. This way if you touch a body or chassis part the wrench in your hand will not start glowing red and catch something on fire (your hand?). A short to earth is a good way to create alot of heat in a hurry.

bob gauff

 

Hold on-
Even plums said his advice for cranking sans fuel was to prime the oil galleries. It is a pretty big stretch to extend that advice to if you "leave the car a while with the battery disconnected". It won't hurt anything, and the battery being disconnected has nothing to do with the oil draining down, but if it makes you feel good, GO FOR IT!

 

Huh, the last two replies are perplexing, say what?!

 

The advice given was specifically for the situation of the OP who was asking about what he should do after he finished replacing his upper cam tensioners. It really has very little to do with whether the battery was disconnected or not. You have to read the advice in context.

 

Ahh, so is my list correct in post #13?

 

If your procedure is whatto do when the battery has been disconnected, AND, secondly. for some reason you need to prime the lube system, then it looks correct. The heading of this thread was what to do when the battery has been disconnected, and that has nothing to do with the lube prime procedure..