‘88 XJS starter relay location and ignition switch

Aaron, the mystery micro-switch is likely to be there so that your cruise control only functions in"Drive". The wire on the driver’s side of the trans. is for your kickdown .

Item 3 of post on this subject couple of weeks back.
Black/green should go from one side of start relay coil to inhibit switch which is at bottom end of shift lever. Should not go to side of transmission case.
I don’t have my wiring diagram in front of me, but guess the black/white might be from the throttle cable kickdown switch which would go to the transmission case. Some other poster can have the wiring diagram open and confirm it.

Seems somebody mixed up the wiring and your starter motor is fine. Nice Xmas present, Santa was in a good mood.

Well, for the time being, I’ve left my temporary ground wire in place and moved on to some other tasks until I can source a 1988 wiring diagram.

Did a coolant flush and used my vacuum refill equipment and I have to say, that’s definitely the way to go on the XJS to prevent air pockets. Just draw 25 in/Hg or so of vacuum, have a few gallons of 50/50 mix coolant ready to go and viola, a completely filled cooling system with no air locks. Granted, this system only works with a leak-tight system but at least if you do have a minor leak somewhere and didn’t know about it, this will help identify a breach somewhere since it won’t hold a solid 25 inches or so of vacuum initially.


I realize this thread is half a year old now but I wanted to write to thank you for your wisdom shared. I took my 89 XJ-S out yesterday and it drove wonderfully. Drove around 100 miles as part of a local Jaguar club eveny actually!

I drove home and parked the car at my house and all seemed normal. But when I went to start the car a few hours later there was no crank and no start. I thought it was unlikely to be the (not too old battery). Multi-tester confirmed plenty of volts there so I had to look for something else. I knew where the starter relay was located already but I followed your tip above. I applied 12v directly to the red/white wire that I undid from the relay. Immediately the car started cranking so I knew my issue was in the relay (or possibly the ignition switch). I replaced the wire and took a rubber mallet to the relay. I gave it 3 good whacks and then tried to start the car. And voila, it started up no problem!

New relay is now on order from one of the usual suppliers and I have the relief of a happy purring Jag once again. Shows the great wealth of the knowledge compiled in this forum!


I am glad that you found my post helpful.

Don’t throw your old starter relay away. Remove the cover and inspect the contacts. I have successfully rejuvenated more than one starter relay by cleaning the contacts with fine sand paper. The contacts get burnt or tarnished over the years but I have been able to get them working properly again with a little time. It is always good to have a known good spare starter relay on hand just in case you have problems again.


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It will definitely go in my parts bin! Any special trick to removing the cover of the relay (I haven’t tried to yet)?

I figures that a new one was a small enough expense I was happy to go ahead and buy it. But hopefully this will leave me with a serviceable spare next time this occurs down the line in this car or some other as you say.

No, there isn’t anything special about removing the metal cover on the starter relay. After recording the orientation of the cover (picture or notebook), carefully bend back the edges of the metal cover in the areas that it was bent at the factory to hold it on, pull the metal cover off, and inspect the internal components for proper operation and the condition on the metal contact points. The points have been darkened on the bad relays that I have done this to. I then clean the contacts with fine sandpaper cut into a thin strip and folded over so that I can it pull between the contacts as I am holding them closed and ckean them both until the contacts are nice and shiny. Then I spray the contacts with a spray electronics cleaner. On some occasions I have applied a thin coating of dielectric grease with a tiny paint brush to protect them from moisture, but I am not certain that made any difference. Reassembly is the opposite of disassembly. Of course test it after this to make sure it works again, then leave it installed or put it on a shelf. Whatever you decide to do, carry the other one in the car for a while just in case the problem happens again. That way you can be ready to swap it out if required.

I have had several “starter doesn’t crank the engine” situations over the past 20 years with our XJ-S, XJ12, XJ6s, and E-Type. Sometimes the problems have been intermittent which makes them difficult to sort out. When they become hard failures they are easier to sort out. The problems have been due to bad batteries, ignition switches, starter relays, wiring connectors, and starters. Once I identified the failing/failed component and fixed/replaced it, these cars were returned to their usual reliable conditions. If the problem was really due to a failing starter and not the relay, then the problem reoccurred, and then it was time to change out something else, possibly the starter. But let’s hope that it was the relay this time for you. You will know that you fixed it when the “starter doesn’t crank the engine” problem doesn’t occur again for a long time.


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I know this is an old thread, but someone might find my experience useful.

Over a three year period of hard starts, crank no ignition and hundreds, if not more, dollars I am now able to start my 1989 Jaguar XJ12 reliably. Initially I had to pump the accelerator pedal dozens of times and try the ignition several times before it would perhaps start. Now it may start on the first attempt within seconds.
I located the starter relay and used a well-known water dispersal/lubricating spray.
It cost me perhaps $10.

I am at a loss why experienced mechanics would not interrogate the starter relay in a starting problem.

Just outta curiosity, what did you think pumping the accelerator pedal did for you?

It would not start without pumping it, ofttimes until you could smell the gas. it did not start without it.

I take it you’re pumping with the ignition on?

Yes, with key in position 2.

You’ll still only get a coupla squirts of fuel with that pumping unless you turn the ign on and off repeatedly while doing it.

Hmmm, thanks for pointing that out. I happened to randomly do that as well.

I’m aware this is an old postage, but it worked for me !. Just got my '86 Antilope Brown XJ SC V12 from Canada a couple of Months ago, it took my wife and me to Sweden and back 6 weeks ago and ran flawless. I live in the Netherlands but was born in Hamilton so that’s why there’s a Maple Leaf above my message. Day before yesterday I turned the key lights worked and a click but no cranking … changed the Battery but this didn’t help and started looking for answers on this forum and read about the the startermotor relay. In my Jag it’s positioned in the right side of the Engine Bay under the windscreen fluid reservoir. Turned the key in position 2 and put a + wire on the red and white wire and she started up right away !. Just ordered a new relay but at the moment she starts up by turning the key, yes I will dismantle it and try to clean and fix it. If this is succesful, I’ll keep it in the car as a back up. Thank’s again guys, Ed

I am glad that the email string from several years ago that I contributed to was helpful to you. Over the past 24 years of Jaguar ownership I have successfully rejuvenated several Lucas Starter Relays as described in this string.


Hi Paul, you’ve been around that’s for sure, thank you for your contributions. My Volvo 1800E came from LA and I own it 37 years now, easy to remember since it’s the birthyear of my daughter. Volvo uses mostly Bosch equipment but also Smith instruments, if possible I’ll upgrade to Bosch or a WOSP High Grade Startermotor from Moss. What’s your opinion on these ?

I have enjoyed being a member of several Jag-Lovers lists since 2000 when I got my first XJ6. I had six Jaguars at one point. I now have a 1969 E-Type, 1990 Series III V12 Vanden Plas, and 1990 XJ-S convertible so I contribute to those and related lists regularly.
I am a strong believer in the original starter designs for these cars. When a starter fails I get a rebuilt original one or have mine rebuilt locally. I have never had any aftermarket “high torque” or “gear reduction” starters in any of my Jaguars and I have read about the many difficulties that others have posted about when they tried to install one. I know that some people like them and are willing to make the modifications necessary to accomodate them, but I see nothing wrong with the original design except maybe for the weight. I removed and replaced the starters in my Jaguars myself with the same design whenever they have failed. As long as I can find rebuilt ones, or have them rebuilt locally, that is what I will continue to do.