‘88 XJS starter relay location and ignition switch


Can anyone advise me on the location for the starter relay on an ‘88 XJS and also what the procedure entails to remove the electrical portion of the ignition switch from the lock cylinder? Have one I’m looking over for a friend and when the key is turned to the RUN position, everything lights up as normal (and the car was previously starting fine) but now all of a sudden when you twist to the crank position, nothing happens. I suspect either the electrical side of the ignition switch has gone bad or the starter relay (or both!). Thanks in advance for any guidance!

The starter relay, Jaguar part number C36611, should be located at the right rear of the engine bay near the bonnet latch mechanism on the inner fender wall. The attached picture shows the starter relay in my wife’s 1990 XJ-S convertible circled in yellow.
I have encountered this kind of problem where the key is turned in the ignition switch but the starter doesn’t crank the engine several times in our XJ-S and in our Series III XJ6s. In addition to the starter, starter relay, and ignition switch which you correctly mentioned, this problem can be caused by a bad battery, corroded battery terminals, bad battery cables, broken wires, and a bad ground. I think that I have experienced at least one of each in our five Jaguars over the past 18 years. In each case methodical troubleshooting and patience determined the exact fault and the cars were back on the road again.


Remember that the first course of action is to simply twist the key back and forth between OFF and START about 50 times. Sometimes the contacts within the switch itself get cruddy.

Thanks guys, I’ve tried the turning the key back and forth several times with no avail. I have a TR6 with the same Lucas ignition switch and I had to replace the electrical portion many many years ago, it looks exactly identical I just don’t recall how it’s attached.

Battery is good, grounds have been checked and cleaned. At first it happened to him intermittently then it totally gave up the ghost, hence my suspicion of the switch or relay.

When my wife’s 1990 XJ-S convertible (5.3L v12) had a “no crank” problem with the engine it happened intermittently at first, so I checked everything as you did but found nothing definitely wrong. I also removed the metal cover from the starter relay and cleaned the contacts. I thought for a while that helped (wishful thinking?), but then one day the starter would not crank the engine at all. Thankfully it was in our garage at the time. I prefer hard failures to intermittent ones as they are much easier to troubleshoot. I purchased a rebuilt starter, removed the failed one, and tested them side by side on my garage floor using a fully charged battery. The old one was completely dead and would not spin at all with the battery connected while the rebuilt one spun energetically when the battery was connected. That was at least ten years ago and the rebuilt starter has reliably cranked the engine many hundreds of times every single time since then. It is still worth checking all the possible components for faults, but it is possible that you have a failed starter. One way to check that it is not the ignition switch or starter relay is to bypass them both and apply 12V+ from the battery directly to the white red wire connected to the starter relay. If the starter doesn’t engage then the starter has failed. If the starter engages then it is a relay, wire, or ignition switch problem.

I believe that your 1988 has a different type of key, ignition switch, and steering wheel lock mechanism than our 1990 so others will have to help you with that.


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Thanks Paul,

I will most definitely check the starter itself. It was just so strange how it quit but the car had sat for quite some time in a collection before my friend acquired it so it is possible that now it has been called upon to work, it decided to give up the ghost.


Paul mentioned bad ground.
The ground end of the start relay coil goes to the inhibit microswitch on the auto shift lever. The lever must be in park to complete the ground.
A common mistake is to forget about the lever, or ( less common ) have a bad microswitch.
The microswitch is not your common or garden $1 type you can buy in a bazaar in Timbuctoo, that would have easily done the job.
It is a special Lucas one.

On the ignition switch topic, once had an intermittent start problem with the 1979 coupe. Found a very small hole in the side of the ignition switch.
Inserted a good dose of WD40 or similar and cured the problem.

The Lucas starter is not the easiest thing to take off the engine, eliminate all other possible failure modes first. The starters are robust but on an 88 car could be an end of life situation.
I have rebuilt a couple of them, just needed a major clean and adjustment of the solenoid throw out, now good for another 30 years and 200,000km.
That does take at least 3 hours, so for most people cheaper to buy a new geared starter.

A common Lucas starter failure is the soldering of the light gauge solenoid winding to the terminal on the end of the solenoid body. They just fracture with vibration and age. An easy fix once you get the solenoid off the starter body, but that means taking the starter off the engine first.

  1. When you switch to START, the white/red wire on the start relay should be at +14V, or whatever you have for battery voltage.

  2. If at +14V and no start, check voltage of white/red at starter solenoid.
    If +14V, then stater is kaput. If not, broken wire ?

  3. If no +14V on red/white, check black/green on start relay which should be grounded thru inhibit microswitch.

  4. Check white/yellow on starter relay is at +14V in START position.
    If yes, then Lucas start relay is suspect and can be replaced with other brands too.
    If not, could be broken wire or faulty ignition switch.
    Also there is a fuse which supplies +14V to the ignition switch, white/pink wire. Not sure which fuse, but if that is blown various other things will not work.

Good luck.


Superb information! Thanks a million for this! Just to be on the safe side, I had SNG Barratt post a new electrical switch for the ignition as well as a relay, just in case. I’ll follow your troubleshooting steps there and definitely hope it’s not the starter itself as I understand they’re a bit of a faff to replace. I’ll keep the thread updated as I find more and will of course advise of what the cure ends up being. I’ll be looking it over the first part of next week so stay tuned!


Remember that there is a pinion adjustment on these starters. Basically, with the starter solenoid energized but the motor not energized, the pinion should stop a bit short of smacking into the end of the housing. This is to ensure that the contacts inside the solenoid are what stops the motion and not the pinion. The solid whack of the contacts keeps them clean and makes reliable electrical contact. If misadjusted, the pinion hits first, the contacts only close lightly if at all, and electrical contact becomes iffy.

The pinion adjustment is via an eccentric pivot bolt. With the solenoid energized, loosen the nut, turn the bolt until the clearance is at the large end of the spec (!) and tighten the nut back down. Recommended to do on new and rebuilt starters prior to installation.


Speaking of which, would it be advisable to fit a gear reduction type starter if that’s the path I need to down? I presume so.

Also, can you advise on removal of the electrical side of the IGN switch?


Aaron, the electrical part of the ignition switch (from memory) is retained with a grub screw (set screw) which you can loosen with an allen wrench. FWIW, the poorest electrical connections on my own car were at both ends of the heavy cable running across the engine side of the firewall. If you check those connections ,with battery disconnected, don’t stop once you have loosened one nut at each end. Keep going and you will find another nut below the first. Self explanatory once you are in there…
Consider the idea of adding an easily replaceable push button soldered into your ignition switch wiring, and mounted beside the panel lamps dimmer switch. I did this and now never use my ign. sw. to start the car.

Oh, yeah, the gear reduction starter is definitely the way to go.

IIRC, the separation of the tumbler from the electrical switch on the ignition switch was readily apparent, a tiny screw in the side or some such. I just recall I didn’t have any problem with it. And the problem is the contacts inside are bare copper prone to corrosion. Brand new ones sometimes are no better, as they’ve been corroding sitting on a shelf for decades. If you have the patience, the thing to do is open the switch up by bending up some tangs. One by one drill out the copper rivets that hold the contacts on the inside to the spade terminals on the outside and replace each one with a small brass screw and nut. When done with that, fire up a soldering torch and solder everything – the spade terminals to the brass screws and nuts, the internal contacts to the brass screw heads, and cover the contacts themselves with a layer of tinning. Reassemble and reinstall.

Thanks for the tips gents. I’ll be attacking it in the next several days so I’ll advise as to what I end up finding. I have a two post lift in my garage so I may just give the starter a couple raps with a hammer before anything (if there’s room in there to do so) before I go further.


My car, although different, is similar in many ways.
Including the ignition switch.

IO found splitting off the electrical part in situ beyond the endurance of my aged shoulders.
Unplugging the harness and removing the switch in it’s entirety worked out rather well

I got it on the bench and made a major mistake. although I worked over a catch pan. A few teen parts escaped, never to be found!!

But, the contacts were well worn. the tumbler was loose.

All attributed by me to age, use and a heavy key ring.

I also found the warning buzzer harness adrift. A PO had been there and silenced it.

A NOS switch from David Boger at everydayxj j fixed a lot of ills.

When restoring the shrouds, I subbed in Allen head screws for the slotted units.

Removing the breakaway screws went better than expected. One reused and the other replaced by an Allen.


Update; replaced starter relay with new Lucas unit as well as electrical portion of IGN switch. Still no joy. Checked for presence of voltage at white/red wire at relay with ignition switch in crank position and no voltage so now I need to figure out my path of access to the starter to check voltage there. Did not check other wires at starter relay as of this post but will also do that and report back…


You DID check your inertia switch, did you not?

Yep, I presume just push down on the little plunger on top to reset? Although I don’t know if those ever give problems otherwise??

It is good that Kirby mentioned the inertia switch. When the pin on top is pulled up so the the red band is visible it disables functions requires for starting. When the inertia switch is tripped in my 1984 XJ6 and my wife’s 1990 XJ-S convertible (5.

3L V12) it disables the fuel pump but the starters will still crank. However in my Canadian market 1990 V12 Vanden Plas in addition to the fuel pump being disabled, the inertia switch also disables the starter from cranking. I am not sure what models and years Jaguar added that feature so it is good that you eliminated the inertia switch as a suspect in your “engine starter doesn’t engage” problem.



  1. it seems to me that the ignition switch is still an issue. Or it is not getting volts to do it’s function.
    Brown always hot to the switch??

  2. To me the phrase of replacing the electrical portion of he switch is a bit ambiguous. External on the switch or inside!! The former easy, The latter far more fiddly. I messed mine up “big time”.

  3. Down and under. Carefully, Jump 12 v.to the starter solenoids r/w terminal. I suspect the engine will crank. Again Caveat on several levels…


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Okay guys here’s an update; I was checking power and ground at the relay and noticed that if I remove the black/white wire off of the W1 terminal and make a ground to the bracket, the car cranks over fine, so that’s where my problem lies.

I gained access to the neutral safety switch in front of the shifter and checked all wiring there and nothing seems amiss. And speaking of which, there are two microswitches up there that the shift linkage butterfly makes contact with. What’s the second one?

So, I finally got the car up on my lift and was checking wiring and I see a single spade terminal on the driver’s side of the transmission case with a black/green wire coming off it it. May I assume this is related?