'93 VDP, assembly date 25 Sept, '92. A couple months ago, whilst replacing the battery, I attached the positive cable, slipped in the trunk (boot) and struck the positive with the ground (earth) cable. Since then , the “Great Beasty” has been silent. The remote door locks function, as do the interior lights, when switching the key to “on” can hear a couple relays, and a small whirring, which I am guessing is the brake booster pump. Absolutely no other electrical activity. I have done the following: 1. Checked all fuses in all fuse boxes. 2. Replaced the Ignition-on relay. 3. replace the body ECU. 4. Replaced the instrument cluster. 4. Replaced the engine ECU. 5. Had the Battery checked for damage. (as new). 6. Tested every relay I could find for function.
Would greatly appreciate any help from the forum, y’all have been an inspiration in the past.
Having beautiful weather here in the Pacific NW, going into Jaguar withdrawal so badly that I almost bought an X-type yesterday. THANKS. Matt
Mat …
My first suspect would be the battery. I know you said it was checked but I would definitely try a different one first.
As you can see the Battery power goes directly to the starter (through the starter solenoid) no fuses. The other side of the starter solenoid gets its power through the starter relay which is energized (through various relays) by the ignition switch. First check (again) fuse C3 in the right fuse panel.
Now go to your starter relay and using a wire jump the load side (poles 87 and 30) of the relay. Make sure the car is in park because you’re now bypassing all the safety relays. Does the starter turn the engine over now?
https://www.jaguarforums.com/forum/xj40-xj81-25/starter-problems-102855/
Thanks Grooveman; I was not specific enough, when I turn the key to first position, Can here relays, whirring. NO other electrical activity, ie no warning lights noe of the gauges fuel, temp, etc., “come alive”, nothing. Fuse C3, rt. side checked ok on ohm meter. Tried the 1 yr old battery from the wifes’ Rover, no joy. Checked all underhood, firewall relays, all function to application of 12 volts with good, solid clicks. Sorry, but am so poor with schematics, just where does the starter relay live? Have checked all the underhood ones I can see, when I had the instrument cluster out, found a couple relays behind it, they both tested ok, were marked as ABS relays, but since I was there, checked them as well. I am certain I can hear Joseph Lucas’ ghost laughing at me. Truly appreciate your help.
Have you checked the fuses in the central glove box? One of those controls the dash instruments.
Mat …
First thing lets find out why the car isn’t even turning over.
The starter relay position is pictured below …
The plastic cubes are the relays. The diagram shows relay #4 as the starter relay. I couldn’t find out which relay is #4 but myself guess would be the yellow one. I have an '89 model so a little help here from you '93 owners.
You get at these by first removing the outer trim panel which has nylon press in fittings along the top and a few bolts. Under that is another panel (metal) which has some screws and bolts. No need to take off the glove compartment door.
Once you get to the starter relay and jump 87 and 30 (theses are shown on the plastic relay cap) the starter should engage and begin turning the engine over. The engine won’t actually start but it will eliminate what isn’t working. Again make sure the car is in park before you do this.
Groove, on the later models, they stuck groups of relays into “relay modules” - often the solder joints need reflowing in these puppies as cold joints are quite common.
The one that holds the starter solenoid relay on the 93 is this one:
it can be opened up without damaging anything and the circuit board checked for a bad joint.
Oh and there’s no LUCAS electrics on the OP’s 93, all HELLA
Larry …
The diagram and picture were suppose to be from a '93 Xj40. So the relay module is used on the '93 ?
Is it located in the same place as earlier models ? As I mentioned I have an '89 so just trusting the pictures I dug up on line of a '93 … fooled again.
Regardless, jumping the starter relay should be the first step in troubleshooting a car that won’t turn over.
Groove - The diagram is sort of 93-94, courtesy of Haynes, but the pic isn’t - not sure what year car that’s from but with those round connectors, it ain’t no 93 
Of course you’re right on about the relay’s role in all this, no matter where the guys at Coventry stuffed it.
Anyway, the diagram describes a module and that is what the OP’s car has, I’m pretty sure about that (unless it’s a 92 registered in 93) however only the VIN knows for sure …
As an aside, the diagram is also a bit off as the fuel pump relay on the 94’s (and maybe the 93’s) isn’t a separate entity but it too is stuck inside the module DBC 10422 along with the high mounted stop lamp etc.
Hi, When I had the interior stripped out of my 93 a couple of years back to change the roof lining I noticed what looked like ’ in line ’ fuses in several parts of the harness dotted about the car. They are sealed in heat shrink plastic and were definitely a factory fitting and not added later by a PO.
Maybe when you accidently reversed the polarity you have blown one of them ?
If Grooveman’s method of jumping the starter solenoid gets the starter motor to turn the engine it could be worth investigating those fuses. I have no idea what they protect and I can’t remember exactly where they are located but I bet Bryan does !
Fuses or diodes? I vaguely remember those and I don’t think they are fuses.
Folks, thanks for all the info. Grooveman, As Larry mentioned, '93 was the MY that they started grouping 4 relays into “modules” and scattering them about the car. My ignition-on relay is located next to the top Left corner of the radiator, with another module at the top Right corner, There’s also one under the Right corner knee bolster, under the glove box. Will open up the starter solenoid one, probably tomorrow, and check the solder joints. Casso, thanks for the in-line fuse info. Haynes vaguely mentions them, but gives no clear info regarding locations. Shall look for them. My VDP must be a bit of a mutt, as in 12 years ownership, I’ve encountered Magneti Marelli assemblys, Hella relays, a couple of Lucas relays as well as Lucas TPS and Engine Control Unit, uncertain which language to mutter in while up to my elbows under the dash. Thanks again all.
From memory, the Haynes Manual will be of no use for >93MY cars.
For relay locations check http://www.jagrepair.com/images/AutoRepairPhotos/94%20XJ12%20Pump%20Relays.pdf
They also had the correct schematics up for the >93 cars, but they are apparently offline. I do have them though.
You will need to trace the voltage supply to different check points in the wiring to find out what’s broken. Could be a fuse, relay or diode.
For my '89 XJ40 I subscribe to a company called Alldata. $29.95 a year You pay for a specific year model.
All the wiring diagrams and information are for that year only unlike the Haynes manual. It’s been a great source of information for me time and time again, especially the very detailed wiring diagrams that run 70 (yes 70) pages long.
I assumed they were fuses because of how they were connected in line, they could have been diodes, I never inspected them closely I was focused on getting that headboard out at the time but I remembered reading about various in line fuses dotted about the car apart from the 3 fuse boxes , and also the locations of them varying from model years in the manual so assumed they must be the ones mentioned.
The online fuses are generally the push in blade type fuses from memory, I am sure Groove can correct me as he is a current owner whereas mine passed onto a new owner a few years ago.
Guido: Not really an excuse, but have been dealing with flu, plus spouse has taken over the garage with her paper crafting supplies, so this is happening in the driveway. The correct email is: crops45@yahoo.com. I left out a letter, sorry. Any way to test starter solenoid in the relay module? Thanks to all the help from the forums’ bank of knowledge. Matt
You can test the relays - there are relays, not solenoids - in the relay module. Start by unplugging the connector from the module and dismounting the module from the two ‘rails’ - the module just snaps onto them.
Then CAREFULLY use a thin bladed screwdriver to GENTLY lift the slotted tabs, two on each side of the module, to release them from the catches. Slide the module apart and you will see the circuit board with the relays. There are pics from the old J-L photo album here: http://www.jag-lovers.org/snaps/snap_view.php3?id=1241575675
You can reconnect the connector and activate the circuit in question. If you see the relay close the relay is being energised. If nothing else is happening the relay contacts could be overly pitted or you could have bad solder joints where the relay mounts to the board. If the relay isn’t closing you can try manually closing the relay by moving the hinged ‘plate’:
And reflow the solder on the underside of the relay assembly for good measure!
Larry
Day17
Mike, thanks for the tip. Pulled the module, and tested as you describe. Nothing. Took the relay board inside and used a power source (12 V, 1 Amp) and the relay responded with a nice, firm click, could watch it close/open. Larry, Visually scanned, with a magnifying glass the solder joints, they look ok, do you suggest re-flowing them anyway? I appreciate the time and ideas all y’all are sharing.
Well that’s a hard call if they all look nice and shiny …but OTOH it only takes about 5 mins if you have the thing on the bench and you have the tools – so can’t hurt, right?