On my 1994 XJ12
The car intermittently fails to start.
The car just makes a 'click" sound and doesn't crank.
waited a day, the car would just start up fine.

Same problem repeated itself off & on.
Had Battery tested told it was fine,

Now the mechanic is saying
the battery is under-powered.

I have read in the forums that
"A very common cause of cranking but no start is low battery voltage.
If the battery voltage sags much below 11V while cranking, the ECM will not trigger the ignition to fire."


But mine doesn't crank at all.

The Battery is a 6 month old Die Hard
Group size 78
CCA 650

Would a "Bigger" battery solve this problem?
What size battery would work better?
How many CCA do I need?


I have gotten the following results from
battery sites.
Group size
T5/47 or H5



But they don't seem to have bigger CCA than the one I already have.


Thanks in Advance
Jeff

 

Hi Jeff,

Your click could indicate that the solenoid on the starter is failing, but there are many other possibilities, and it may be a combination of several issues.

The ignition switch is known to fail. The next time the no-start happens, try wiggling the key to see if it makes any difference. You can also test the switch from its electrical connector inside the steering column cowl, and replacing the switch is not terribly difficult. See the photos at the link below:

Welcome to Jag-lovers - Members Photo Viewing Page
Welcome to Jag-lovers - Members Photo Viewing Page


Also try wiggling the gear selector lever to be certain it is fully seated in the Park position, and if that doesn't work, try starting the car with the transmission in Neutral. If so, you have a problem with the Park-Neutral switch.

Another possibility is that corrosion on the battery power connections and ground points throughout the car is interfering with proper battery charging and reducing the voltage/current available for starting. It would be worth testing the voltage across the battery terminals and comparing that figure to the voltage measured at the starter. Even a small drop in voltage can indicate losses due to corrosion or other issues.

The battery power positive cable connects the battery in the trunk/boot to the fuse boxes in the passenger compartment, the main firewall battery jump-start post, and the starter and alternator. It is worth cleaning all of these periodically, especially the connections at the battery, firewall stud, starter and alternator. The battery negative cable connection to the body and the engine ground strap should also be cleaned. Corrosion on various ground studs can also cause problems. See the photo albums at the links below for more info:

Welcome to Jag-lovers - Members Photo Viewing Page
Welcome to Jag-lovers - Members Photo Viewing Page
Welcome to Jag-lovers - Members Photo Viewing Page
Welcome to Jag-lovers - Members Photo Viewing Page
Welcome to Jag-lovers - Members Photo Viewing Page
Welcome to Jag-lovers - Members Photo Viewing Page
Welcome to Jag-lovers - Members Photo Viewing Page
Welcome to Jag-lovers - Members Photo Viewing Page


Other possibilities include cold or starved solder joints in one or more fuse boxes or relay modules (for example, the Starter Relay is in one of the 4-relay modules behind the passenger-side knee bolster, and those modules are notorious for bad solder joints). Reflowing and adding solder to the joints can solve numerous hard-to-diagnose symptoms. Here are some photos that show some of these components:

Welcome to Jag-lovers - Members Photo Viewing Page


The Ignition On relay is in the center console in the vicinity of the radio. The base is black and the original relay has a Light Blue cover.

The Haynes XJ40 Manual is a handy reference and you can download a pdf version that is missing a couple of chapters but has the relay location diagrams here:

https://www.mediafire.com/?hx8bttsy4kxxr


Sorry to overload you with information, but hopefully something mentioned above will help you narrow down the problem. Other members may offer additional ideas.

P.S. I'm running an H5 size Walmart battery in our '93 and it's not great, but it's made by Johnson Controls, the same company that probably made your DieHard, and also is rated at 650 CCA (there are only three or four battery manufacturers left in the U.S. and between them they make all the brands).

Cheers,

Don

 

Thanks Don,
That is a lot of information,

I did forget to mention my mechanic removed all electrical fuses and such and made sure they were making contact.

I will have to look at the corrosion issue a little more carefully but haven't spotted any to this point.
I know about the gear selector lever, fully seated in the Park position issue and don't believe that is it.

It could be the that the solenoid on the starter is failing, thanks for the suggestion.

As far as the battery goes, does the size matter or is it all about CCA ?

Thanks for the links & photos they are Always Appreciated!
Jeff

 

Not that your problem is definitely attributable to the fuse boxes, but fuse failures rarely occur across the fuse terminals but from the fuses to the harness connections at the back.
These connections pass through a pair of circuit boards which often exhibit cold or starved connections, especially on late cars.

Larry

 

Hi Jeff,

As Larry has already mentioned, the problem is with bad solder joints on the circuit boards inside the fuseboxes. I think some of the photos I linked to may show what I mean.

You probably won't notice it until you've disassembled the battery power and ground connections and inspected them closely for thin oxidation. In the article at the link below on voltage drop testing, the author claims that an increase of circuit resistance from 0.11 ohms to just 0.17 ohms will limit a 120 amp alternator to just 80 amps output:

Voltage Drop Testing


I think in general, a battery with a larger physical size can have a greater CCA rating, but a Group 78 battery is physically larger than an H5, so unless you've got room for an even larger battery, you're probably already at the limit. I'll be honest, I don't think batteries are made as well today as they used to be. I don't know what is different, and I may be wrong, but the batteries I buy today for our '93 just don't seem to do the job or last as long as the batteries I was buying in the '90s. But all of that said, I suspect your problem is not the battery itself, but issues in the charging and/or starter circuits.

I'm sorry there's no simple answer, but if I were you, I would start by disconnecting the battery positive and negative cables, then thoroughly cleaning the following connections:

Battery terminals
Battery negative cable connection to the body
Jump-start post on the firewall
All connections at the starter
All connections at the alternator
Engine ground strap - both ends
Test the starter solenoid while you're working on the starter connections

If the solenoid tests okay and things still haven't improved, I'd move on to cleaning the battery power connections in the outer corners of the footwells and at the fuseboxes, as well as the grounds used by the Engine Control Module (ECM). I don't know where they are on a V12, but on our 6-cylinder there are two on the intake manifold studs and one on the firewall right behind the cylinder head. You can download the 1993/94 XJ Electrical Guide here:

http://www.jagrepair.com/images/Auto...ec%20Guide.pdf


If things still haven't improved, I would look at the Ignition On relay, the module that includes the Starter relay, and the ignition switch.

Cheers,

Don

 

I tend to agree with you, I don't think its the battery
I will look at the car this weekend.

Thanks for all your advise
Jeff