Good day to all.

Being a jaguar enthousiast i decided to take the cat out yesterday (1998 xjr) Been using it every day since little less then a year until,...
Driving on the highway, at 80mph, a load bang, front right.

The engine cut out straight away all electronics gone, except lights, radio, doors windows (BMC seems to be working i guess) all other modules offline, no way to communicate with them through odb, nothing. car doesnt start, neither the parking relay. and an endless list of errors, gearbox, ABS, suspension, ....


I brought it back home on a truck, managed to get it out of parking, opening up the trim and using the screwdriver.

All a bit weird cause even without the car runing your able to get it out of parking.

Please help me on this one, before i start changing all the electronics :-)

 

You don't need to remove the trim to release the shifter from P. Just unscrew the cap with a star shaped recess on it and use the key to push down an internal lever.

Can you still crank the engine? If it cranks, does it make any loud knocking noises?

 

Thanks for the reply,

No it doesn't crank at all.
I was thinking maybe the starter motor blew up and/or the solenoid, wich then prohibits any current being distributed to the primary computer and fuses .... or this a long shot...

 

The big fuses on the positive battery post have a habit of coming loose




the next question is the battery and if it's been tested

Do you have the ability to put a meter on the B + post of the running alternator ?

After that we will step by step establish power on the points of the car




Editing

 

I thinking about the loud bang can you get a socket on the crank. To see if it is locked up?I remember spark plugs coming loose..?in the old days.

 

This common to fail bulkhead connector that’s on the right front deserves to be checked out for looseness, charring & overall broken contact. That might explain why you have some power but no crank. If you have to do any repairs here, disconnect the battery first.

 

This happened to mine. Thankfully was discovered in the shop at the time. Definitely check that. The part from Jaguar was only like 65 bucks.

 

LOUD BANG?

Did the inertia switch trip?
Try a reset?

 

Hi

I checked the starter relay, changed it over with another one, no difference.

All connections are sound and ok, The main fuses under the spare wheel also.

mmmh The Cat doesn't want come to life.

 

Thanks,

But no the connection is sound nothing happened there ...
now gonna go off trying to crank the engine

 

maybe alternator blew up ?

 

Hi, yes that crossed my mind but im still having the windows doors central locking, all working just the engine control manual does not come online and i cant even communicate with that through the foxwell or any other odb.
checking the fuses in the engine bay, told me they only get power if the relay is activated. so i guess after that the engine starts.
i just hope its the start motor that blew up, but why and how ...

 

Hi
where is this inertia switch located on the cat ?

Thanks

 

With the key in the run position before the start position we can check for power control on the points of the car

The fuse boxes have a relay in them that close with the ignition key

You can rock them in their sockets and feel them clicking

In the picture above the realys are called :

Engine " compartment " fuse box - ignition positive relay

LH Heelboard fuse box - ignition positive relay

RH Heeloard fuse box - auxiliary positive relay

Trunk fuse box - none

You can swap relays to get them to click confirming you get the correct command from the ignition switch

not all fuses and their subsystems in the fuse boxes rely on these relays to pass power through and are hot at all times with a direct connection to the battery

If a relay does click it can still be bad in the power contacts inside being burnt not allowing proper current to run your devices

An example would be the starter circuit

In order to get the starter solenoid relay to click closed.........

We will look at page 37 of your wiring guide

http://www.jagrepair.com/images/Auto.../jagxj1998.pdf

# 3 / 25 amp fuse engine " management " fuse box - this fuse is hot at all times and no connection relay

# 5 / 10 amp engine " compartment " fuse box - this fuse is hot at all times

Editing , my wifi keeps dying

The EMS relay on page 31 ............

The EMS control relay is powered at all times as well as the contol power to it's pulling control coil

The control coil must get a commanding ground by the ( purple / pink ) wire on page 39 labeled with a flag as EMS control Relay on the left side of the print

Therefore the Engine Control Module must be powered

This ECM power comes from................

# 10 / 5 amp engine " management " fuse box - this relies on the EMS control relay to close

and # 5 / 10 amp engine " compartment " fuse box - this relies on the ignition positive relay to close in the fuse box

Correct , this ignition positive relay does get a command ground from the ignition key


This would be pin 3 to 5 on the switch side of the connector

pin 5 on the car side of the connector is a car frame ground that needs to be checked and I had corrosion on mine

The car side of the connector lifts straight up for easier working


They're not making it easy

 

Hi how does this EMS relay gets its power ? somehow through the ignition key maybe

thanks

 

Thank, im really discovering a lot of the cat this way
Checking the fuse box, holding a ground to the engine and possitive to these fuses, the ones in black dont get12V (fuses are ok of course)
They should be under constant 12V with the key on ?

 

Fuse 10 , 12 , 14 , 16 .

See page 34 and 31 for LH heelboard fuse box

Point 2 circle double hash requires the ignition positive relay to close ( brown one in your pic ) does it click with key rotation ?

This command ground would also be pin 5 to 3 on the ignition switch

See page 36 , notice the inertia / crash switch which can trip from a road bump

This switch does not always reset when you press it

You can put a paper clip in the connector between the 2 white wires



................

 

Thanks ever so much !!!!!!!!!!!!!
It turned out to be the inertia switch. €€€ down the drain for the towing truck but very happy for all your help.
The cat purrs again and ... im getting to know her better and better.

 

So, what was the "loud bang, front right"? Did you hit something on the road?

 

Motorcarman nails it again!