XJ40 No start
 

Hello from France!
My Xl40 refuses to start!
Battery is ok; all lights enlighted at the dashboard; no fail shown on the computer

All equipments (doors, wiper, radio, head lights, blowers...) are ok

BUT no current when the key is turned to the starting position.
One relay under the passenger panel (the one on a purple base) is very hot; it seems it is powered all the time; same for the relay located under the radio inside the central panel.

All fuses (left/right/central panels) are ok

I would be grateful for any search direction!
Cheers
Michel

Michel, just to be clear, are you saying the engine doesn't crank (turn over) when you turn the key?

Larry

Maybe check the ignition switch behind the lock cylinder? Was it starting/ operating normally up to this event? If something inside that switch broke, it may be causing an extra 12v where it shouldnt be... Good luck..

absolutely; nothing happens when I turn the key; no noise, nothing.

Everything was functionning "before"; the only thing I need to mention is that I did connect the battery to a charger (battery was empty after a long period of inactivity of the car).

Do the headlights dim when you try to start the car?

Sometimes, if a battery is worn out or has an internal problem it will work enough to switch on the accessories, (lights/blowers etc) but when the demand is highest (starting the car), it will fail and you would get no engine turnover.

As the battery in your car is old and been in a discharged condition for some time, my first step would be to get the battery tested or try a replacement battery.

There is only one way to test battery performance under load (starting) and that is to perform a drop test with a specialty tester across the terminals.

A battery supplier should have one of those.

Good luck

Larry

Check the inertia switch, it is really easy to trip by accident..

Maybe try disconnecting the battery for a few minutes. It's free and easy and might just shock a stuck relay into obedience.

I guess that if everything was working, and charging the battery doesn't help, then the battery would be my first suspect. My 2 cents worth.

Hi Michel,

Here is the starter circuit for your 1989 XJ40:

https://cimg2.ibsrv.net/gimg/www.jag...4bd9922acd.jpg
https://cimg1.ibsrv.net/gimg/www.jag...2901997a22.jpg

You can find this on pdf page 15 of the Electrical Guide, which you can download here:

Jaguar XJ40 Electrical Guide 1988-1989

Before I go through a long explanation of the starter circuit, I would say that the most likely causes of a sudden no-crank condition are low battery voltage (as previously mentioned), the gearshift lever not being fully seated in the Park position or a problem with the Park/Neutral switch or Start Inhibit Relay, a problem with the starter relay, a problem with the ignition switch.

Another not uncommon problem is that if you try to start the car with low battery voltage, the starter gear can jam against the flywheel but be unable to rotate the engine. If you suspect this may be the case, you can try tapping the starter case with an extra-long socket extension or other object long enough to reach. Just take care not to touch the electrical connections.

Try starting with the gearshift lever in Neutral to see if the problem is the Park/Neutral switch.

The Starter Relay is the one in the yellow base on the component panel behind the passenger knee bolster. Try swapping it with the one in the green base for the A/C & Radio. The relay in the purple base that you said is hot is the Main Relay, so it should be on anytime the key is in the ON position. The relay in the blue base is the Ignition On relay - it powers a lot of accessories and such, and since you have lights on your Instrument Cluster I think we can assume for the time being that the Ignition On relay is working.


https://cimg3.ibsrv.net/gimg/www.jag...b5d82b19c5.jpg

The diagram above is from pdf page 165 of the Haynes Jaguar XJ40 Repair Manual, which you can download here:

Haynes Jaguar XJ40 Repair Manual

Please keep us informed.

Cheers,

Don

Michel, we are wondering if you have started your car yet..

Thanks every one for your explanations inputs and documentations; I am currently away from home, and thus just studying the provided material for future use. I'll keep you informed.
Regards