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JagDoc
JagDoc, European Shop Owner
Category: Jaguar
Satisfied Customers: 6426
Experience:  20 years of experience working with Jaguars. Independent European shop owner and technician.
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Jaguar XJ8 L: The same Jag has always had a battery drain problem.

Customer Question

The same Jag has always had a battery drain problem. If the car is driven everyday, there is usually no problem the next day. But if it is not driven for, say 2 days, or if the weather is colder, the battery is dead in the morning. The battery is new. But now, I have the battery charged, and the car sounds like it is turning over. But I believe the starter is the sound I am hearing. Right under the driver when I leave the door open. In the old days, I would think this was a bad solenoid not engaging the starter. I also wonder if a bad solenoid could have been shorting out and draining the battery. Any thoughts?
Submitted: 1 year ago.
Category: Jaguar
Expert:  JagDoc replied 1 year ago.

JagDoc :

Hello, I'm Jason. I will do my best to answer your question quickly and accurately using the information you have provided.

JagDoc :

well, in cases like this, I like to start with the absolute basics...


 

JagDoc :

I'd like to be sure that the battery is completely fully charged during a start attempt


 

JagDoc :

and if so, is full voltage getting to both the large power cable to the starter, and when the key is in the start position, does the small terminal get power as well


 

JagDoc :

Either way, I've never had a case of a starter causing a battery drain.


 

JagDoc :

Here's a draw test procedure that I recommend for the battery drain


 

JagDoc :

Open your hood, and then manually re-latch the latch using a screwdriver or similar (we're re-latching so that the alarm computer will think all latches are closed). Open driver's door, and also re-latch. Open trunk, disconnect negative lead from the battery and manually re-latch trunk. Set your multimeter to the A or mA setting, and place your meter leads between the battery cable and battery post. You should then see how much current is drawing on the battery with everything off. Write down, or take a note of the amount of current (ex: 550mA). Then open your fuse panel cover. Start with fuse 1, remove the fuse and look at the meter. If there is no change, reinstall, and move onto fuse 2. Repeat this process until you see a significant amp drop on the meter. You will then know the circuit that is drawing down the battery. Look at the fuse legend, find out what is on that circuit, reinstall the fuse, and then unplug any electrical consumers on that circuit until you find out what specific component is drawing on the battery by unplugging them one by one until the amp reading on your meter drops below 50mA

Expert:  JagDoc replied 1 year ago.
Our chat has ended, but you can still continue to ask me questions here until you are satisfied with your answer. Come back to this page to view our conversation and any other new information.

What happens now?

If you haven’t already done so, please rate your answer above. Or, you can reply to me using the box below.
Customer: replied 1 year ago.

OK, I will try that to see if I can find the battery drain. The starting problem definitely sounds like the starter. I can hear it trying to turn over underneath me while I have the driver door open. It doesnt feel like the engine is turning over at all. As I live in Wyoming, we dont have any Jaguar dealers nearby (Denver is 400 miles away and Salt Lake City is 380). Any parts suggestions would be appreciated. I also have been trying to find a windshield washer tube connector (the connector that connects the wiper hose to the engine hood. I have had no luck. I will get back to you when I complete the drain test.

Expert:  JagDoc replied 1 year ago.
Sounds good. Let me know how it goes
Customer: replied 1 year ago.

I'm not really good with a meter, but I used the 20A setting. I had the choice of 2, 20, or 200ma. On 20, I got a constant reading of .41. I could not flip the latch on the hood, so most of the test was done with the hood closed and the left rear door manually latched and the trunk manually latched. When I checked under the hood, I noted the differences on the meter and looked for any changes. The only time I saw a change was when I pulled the left door control module and the left door (sorry, I can't remember the name, some type of control with high amp fuse). I ran out of time and did not get a chance to check the right rear door fuses. Anyway, when I pulled each of the fuses for the left door control, the reading went down to .18 - .20 This is all I could find. I also took note of any blown fuses (none). I still think the starter is not engaging. Thanks

Expert:  JagDoc replied 1 year ago.
Yep, that's still too high, but likely unrelated to the starting problem. It will be a bit more accurate if you use the 2A setting, since your current draw is less than that. Other than the door fuses, did you pull and reseat all of the others?
Customer: replied 1 year ago.

I did. My son looked at the car and showed me that it is turning over but it sounds funny, like it is not getting spark. I have had the oil changed regularly and the oil looks good. The drain problem has been going on a long time, but the car would always start. This is just sudden. What is the best way to check for the spark?

Expert:  JagDoc replied 1 year ago.
If it sounds funny, it's likely not a spark problem. However, you can remove a single coil, plug a spark plug back into it, ground the plug, and crank the engine over.
Customer: replied 1 year ago.

By funny, I mean it is just turning over and over. The belt is turning, etc. but it does not seem to act like it is trying to start. We checked the injector rails at the "tire like" stem and gas shot out when we depressed the pin.

Expert:  JagDoc replied 1 year ago.
and spark? I outlined the method to check spark.

Also, just because there is some fuel pressure, doesn't necessarily mean that it's got enough pressure to start the car. A gauge is best here.
Customer: replied 1 year ago.

I am trying to get it to a mechanic. They would not tow it the 1 mile needed because the book says there are specific ways to do this. Also, as late as Friday I was always able to turn the key to on and put the car in neutral. But yesterday, I could not do it and is make a deep bell toned sound. Is this a clue as to the problem. The battery was low again and I have it on the charger. I'm actually getting frustrated. The mechanics here of course have little Jaguar knowledge, but towing the car to Denver is probably not an option.

Expert:  JagDoc replied 1 year ago.
Flatbad is the only proper way to transport these.

The bell sound is just the computer letting you know that it's not in park.

With a draw test, Jag knowledge isn't absolutely necessary. Draw tests are performed the same way for every car, so this shouldn't be overly difficult to nail down.
Customer: replied 1 year ago.

After charging the battery again, the car goes into neutral just fine. One thing I havent tried (I'm in my office and just thought of it) is activating the security system by auto locking/unlocking it with the key fob. Could the security system keep the car from starting? Is there a way to bypass it to check?

Expert:  JagDoc replied 1 year ago.
Absolutely try to lock/unlock, but it's almost impossible to bypass the system, even by an experienced tech.
Customer: replied 1 year ago.

I will try it, probably tonight, and get back to you.

Expert:  JagDoc replied 1 year ago.
Sounds good, thanks
Customer: replied 1 year ago.

It didnt make any difference. Do you want me to try to record the sound of the starting? It seems like a scaled down version of the usual sound.

Expert:  JagDoc replied 1 year ago.
sure, we can try that
Customer: replied 1 year ago.

I am having a mechanic work on this. He will first try to test things at my house and if needed, I will have it placed on a flatbed and taken to their shop (which is 1/2 a mile away). I will see what they find and get back to you with any suggestions. Sorry this is taking so long.

Expert:  JagDoc replied 1 year ago.
Sounds like a plan, and no problem with the length of chat. I've got customers with car issues that take a month or two to work out.
Customer: replied 1 year ago.

The mechanic says the problem is the computer. I am assuming this is the engine control computer. He is looking for a replacement and so far has found used units for about $690. I have looked on ebay and have found them for $90 - 150. Of course I know the dangers of ebay, although I have generally had good luck.


 


The mechanic says the computer is causing the car not to start and it could be what was causing the short as well. If you agree, would you have a part number suggestion? I have a manual subscription to Mitchell manuals and can look it up there as well. What do you think of all of this?

Customer: replied 1 year ago.

I also notice there are 2 ignition control modules. Could these affect the starting as well?

Expert:  JagDoc replied 1 year ago.
The computer shouldn't affect engine cranking at all. Starting sure, but not cranking. Ignition control modules will also affect starting, but not cranking. Also, if a computer is replaced with used, the used computer will have to be coded to the car using a Jaguar scan tool.
Customer: replied 1 year ago.

The car cranks fine, it just won't start. Is there something else they can check.

 

 

I haven't heard anything from you. I told them about having to program the computer to the car and they have basically punted.

Customer: replied 1 year ago.

Any updates?

Expert:  JagDoc replied 1 year ago.
Sorry, for some reason, after your last response, the question showed on my screen as manually closed.

Let's go with the basics here.
1) is there spark at the plugs while cranking?
2) is there fuel pressure?
3) does the engine sound any different than normal while cranking?
Customer: replied 1 year ago.

I havent been able to get anyone to check the spark. I will try my son again. The fuel rail has plenty of fuel (when checking the tire pressure like valve). When the car cranks, it sounds normal, although I think it sounds like it lacks muscle. I'm sure that is confusing. I am probably used to it turning over in the process. The belts, etc.. all turn and it turns as long as you hold the key all the way forward.


 


If the problem is the computer, would replacing it allow the car to start? No one has a programmer for the car. Would the performance just be affected until it can be coded? Or am I basically screwed?


 


My wife always wanted a Jag because her grandfather had one. I had to buy a used one because we couldn't afford new. Also, her grandfather lived in California and Arizona, where Jaguars can exist in the wild. I don't want to have to flatbed the car 400 miles to Denver, but I will for my wife. Unfortunately, I fear the repair cost will be out of my range. If you have any networking capabilities with other Jaguar mechanics, I would appreciate it if you can identify one in Billings, Montana (200 miles). Of course, the ultimate would be if we could solve it ourselves, but I am losing hope. And $45 is not worth it for you. If we do solve it, I will definitely increase the amount. Thanks.

Expert:  JagDoc replied 1 year ago.
Ok, the spark thing is easy. I want to check spark before moving onto other possibly expensive repairs.

All that needs to happen: unbolt one of the coils from the valve cover, keep the wiring harness plugged into it, have another spark plug handy, ground the ground electrod of the plug to something metal on the engine, and crank the starter. Look for spark
Customer: replied 1 year ago.

OK I will give it a try

Expert:  JagDoc replied 1 year ago.
Thanks.
Customer: replied 1 year ago.

The mechanic checked it and it has spark. I am trying to find out about fuel pressure.

Expert:  JagDoc replied 1 year ago.
Once you find if it has fuel pressure let me know.
Customer: replied 1 year ago.

What is the best way to find out about efficient fuel pressure?

Expert:  JagDoc replied 1 year ago.
With a fuel pressure gauge on the fuel injector rail.
Customer: replied 1 year ago.

OK, I will get one and check it.

Expert:  JagDoc replied 1 year ago.
Thanks
Customer: replied 1 year ago.

Get ready for a completely ignorant explanation of whats going on at this point:


 


The used car dealer (where I bought the car) bought a flatbed trailer and hauled the car to his shop. He also recently hired a better mechanic. The mechanic found that there was a seal that was leaking (not sure where) and that leakage was causing the compression to be low. I also think he said the leaked fluid was pooling somewhere and either the low compression or the pooling was causing the car not to start. He said he needed to replace the seal (s) (gaskets?) and everything should be fine. He will also replace the fuel and air filters. Total cost for seals about $190 and about $750 for everything. I don't know if this will address the battery drain (short), I doubt it. But I cant afford more expense at this time.


 


So what do you think?

Expert:  JagDoc replied 1 year ago.
Here's what happens to these older V8's when they sit for a while, and a bunch of start attempts happen. You actually get fuel washdown of the cylinders, and low compression as a result.

My suggestion (if you have spark and fuel pressure):
- change the oil and filter
- change spark plugs (Bosch 6724 only)
- try to start the car

Make sure the battery is completely, fully charged. Meaning at least 700cca. Even have a charger on it, before you attempt to start. Try to start the car. A long cranking session (sometimes 30 seconds) might be necessary. Hold throttle wide open if it's close to starting but not quite there.

No, this will not solve the battery drain. The procedure I posted originally will narrow this down.

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