I’ve been having intermittent no-start problems with my 2005 XK8. When it has happened, everything electrical is dead when I try to start the car — EXCEPT for the little airbag warning light. I get no dash lights, no odometer readout, no windows, nothing else but the airbag light. It first occurred last year and I assumed it was problem with the battery since it was the original battery to the car ) with 115,000 miles on it). Put in a new battery and nothing changed. Tried disconnecting the negative cable and touching it to positive. Nothing. Repeated that a few times and eventually the car started. Happened again a couple of months later. That time, disconnecting the cables and touching them together worked. Car started and hasn’t happened again until now. Recently, the car sat idle for two weeks, waiting for me to fix a coolant leak. Today I tried to start it and it was the same thing — again only the air bag light was on. The battery showed a 61% charge, so I charged it for a few hours and then touched the cables together and it still won’t start. But this time, all the lights and accessories function, the bells ding and all looks normal. HOWEVER, the digital odometer does not appear and I can’t get the shifter out of Park. Bypassed the shifter lock into Neutral and it did not help. Battery is fully charged; no clicks or cranking, just silence. Then, when I turned the ignition off and removed the key the two little idiot lights on the oil and battery gauges remained on. does any of this sound familiar to anyone? Any suggestions? Thanks!

P.S. Just went out to reset my windows and found that not only are the two idiots lights still on, but there is power to my front windows with the ignition off. Still no odometer readout. Curiouser and curiouser.

 

This points to ignition switch problems.
First question, does the pin which closes with key out, close right now key out?

While I wouldn't think that would allow any circuit to energize that wouldn't energize with key in engine and ignition off, it'd sure explain a battery drain.

Look inside the keyhole. It's a gray pin.

Next thing I'd do is remove all the battery terminals, grab a wire brush, some very fine sandpaper, polish the connection shiny.

Almost forgot, 66% is really low for our cars. Do you have a charger? Put it on top off battery.

Some of us have found the negative battery cable has corrosion, others found the terminals in the trunk at end of battery cables get corrosion.

I'll keep thinking on it.

John

 

John,
What is the purpose of the pin? Never encountered it before.

 

Oh, that's easy - it tells the car key is in. Among preventing the car from "going to sleep", it is the culprit for that annoying ding ding ding when key is in, door is open!

There are a few other circuits active with key in ignition off too.

Plenty of us have tracked battery drain to this culprit.

John

 

Lube that ignition switch key flap with powdered graphite. It must properly slide open and closed as the key is inserted and removed in order to avoid a battery discharge. I try to remember to lube the flap at least three or four times per year....

 

In the boot is a "MEGA fuse" set up. One is 250amp, the other is 500 amp. The 500amp routes to the starter, and stuff - the main circuit for starting and charging, and the 250 feeds most if not all of the fuse boxes and their associated electrical systems.

Open the boot, remove the battery panel, the main cover for the spare and then the spare itself. If yours is like my 2002 you see a dual black box set up. Check EVERYTHING around this mega fuse set up for corrosion or loose wires. Also check the main negative cable to the battery.

From there,,, there is a B+ junction just under the center console on the RH side. If it ain't in the boot, next stop may be there

Also, there is kind of a "main relay" in the fuse panel at the LH door.

There is a lot on the list, but none of them are too hard to get too. Just takes a little digging...

 

Thanks, Jay. I'll check them.

UPDATE: Went out this morning and reattached the battery. This time the dashboard behaved normally: everything that was supposed to be lighted was, even the digital odometer. HOWEVER, when I turned the key, I got a snapping or popping kind of sound and the dash went blank. Disconnected and reconnect the battery three times and each time the result was the same -- no cranking and a blank screen

UPDATE #2: Let car sit with battery connected for a couple of hours. Tried starting and it started and ran fine. Restarted it several times and drove around for a half hour and all is well, as if there was never a problem. On one hand I am happy the car is working. But on the other, it makes it tougher to figure out where the fault lies. I will be holding my breath waiting for it to occur again.

Thanks for the help.

 

Hmm...
ya either have a seriously loose connection,,, a seriously corroded connection - or both. Then, it could be worse than that.

Imagine,,, you're doing 70mph down the bi-way when it happens and the car completely shuts down... 😖 Not a good thing. Brakes, steering all different - no turn signals to let others know your urgent intentions...

Fix it, Brother. Fix it.

Open the hood. On the RH side there is a thing called a false bulkhead. A roundish cubby at the end of the engine bay nearest the windshield. There is a plastic cover over the cubby. On the outside wall of the cubby (engine side) if you look down you will see a large thick black wire bolted into the WALL of the bulkhead. Put a 13mm wrench or socket on the bolt. Turn it off. Make SURE not to drop it... Clean off all 4 faces of all attached cables, the bolt and the washer. Use 220 grit sand paper, Emery cloth, steel wool, what you have. Reconnect and turn it down firmly.

Do the same in the boot with the mega fuses I mentioned. Do the same with battery cables and the end of the cable from the negative battery cable to the bolt on the body of the car. While youre there, take a 10mm socket and undo the two posts there and clean all them grounds up as well...

I'm not usually the fear factor worry wort dude... But I'll say, you're flirting with real trouble if you're waiting for you car to die electrically while you're driving. Jus say'n...

 

That's definitely a symptom of a poor/corroded connection.

As Jay suggests, start at the battery connections in the trunk. Pay attention to the ground wire as the crimped connections can look OK when they're not. Are there any signs of heating up at the connectors?

Follow the positive lead from the battery through the mega-fuses forward. It's going to be somewhere in the starter circuit as everything seems OK until you engage the starter.

 

Thanks all. On the surface the connections look good, but I'll be going over all of them.

 

Stamford, you probably know this already, but for the record: I've seen numerous examples of practically invisible corrosion thwart a 12volt force. 12volts - when you get down to it, that's just not much "push" as EMF (electro-motive force) goes!

Keep us posted! John

 

Indeed. Likely will be an easy fix... once I find it.