My 1986 automatic Series III 4.2 has recently been intermittently failing to crank. I thought I had made a diagnosis of heat affecting the solenoid + starter motor—having been stranded several times after a 30 minute journey—and replaced the Lucas starter motor with a Mazda one. Then it happened again! Just a whining sound, with a click beforehand.

Randomly I think I have found a working solution, though it makes little sense to me. If I have locked the car, (central locking is installed), which I only do when away from home, and then unlock it, the car fails to crank. But if I move the selector into D, then attempt a crank, and then move it into N and attempt a crank: hey presto, it cranks! I discovered this having been stranded yet again. It has since then worked twice in this way after displaying the same symptoms.

Any thoughts? I have no idea where to begin.

 

have you had the car from new? if not - is it possible there's a anti theft system somewhere that's decided to give you grief?
the whine sound - does it sound like the starter motor is spinning but not engaging?
My partners car started doing something similar when motor hot from a reasonable drive, one time i poured cold water on the solenoid & it started.
another test you can try is to setup a push button start directly connected from the battery - button - starter motor & test when motor is hot in park of course.

 

Welcome to the forums Jaguar&MG,

I've moved your question from General Tech Help to XJ6 & XJ12 Series I, II & III forum. Members here with the same model will be able to help.

Please read the guidance for new members ( https://www.jaguarforums.com/forum/n...ned-up-241802/ ) which answers many of the most frequent questions about getting started (on the forum - not the car!).

Enjoy the forums.

Graham

 

Thank you for moving the thread and thank you for the help and advice. I have had a tiresome day so far as it began as a crank-and-start day and is now back to a no-go situation.

I have not owned this car from new (it has been about 4 years now) and I am pretty certain there is no anti-theft device. It may be something to do with the Neutral Safety Switch but I am still guessing.

Any further suggestions gratefully received.

 

Hi, it’s either a faulty start inhibit switch which prevents the car being started in any other gear rather than P or N, basically nothing happens when you turn the key, This switch earths and thus energises the starter motor relay , easy test is to bypass the starter relay and put 12 volts direct to starter motor. If you are getting a whirring noise and occasional starting then its either a faulty starter motor if you are lucky or unfortunately worn teeth on the drive plate which means a gearbox out job to replace. Hope this helps, good luck.

 

When mine was doing this, it was the starter relay on the firewall, can’t remember the colour of the wire right now, but the test( and the way to get it running )was pull the wire that goes From ready to starter and touch it to the battery positive post!, if car starts, you have found the issue and also got it running to get you home!

 

Thank you, I have found the problem now and have the work-around. Now to solve it—eventually!

 

Was it the switched ground wire from the shifter switch to the starter relay? I had this issue the other day and swapped the wire to a permanent ground rather than from the shifter position switch. It means I could start the car in Drive if I wasn't paying attention, but at least the car will start! On my vehicle (series II XJ6) the switched ground was on the relay located in the center of the firewall, the connection closest to the firewall on the driver's side of the relay.