20 Most Recent 1998 Jaguar XJ8L - Page 7 Questions & Answers

This problem could be a number of things. Let's start buy checking for light bulbs that are not going out when car is shut off, such as under hood lid, under trunk lid, inside of car that are hard to see, such as lights that usually stay on till you leave car but normally go of after a few seconds. You can tell buy waiting a while, they will be hot to touch. If this is so this is your problem.
Next check alternator, get an ohm meter, start car, set ohm meter to about 20 volts, and with car running put ohm meter cables red to positive of battery and black to negative of battery. This test should let you know if alternator is working and good if reading is between 13- 14.50 volts, if you do your alternator is good,if not alternator is problem.
Next check the battery with ohm meter. With ohm meter set the same way to 20 volts, and car off , put red lead to positive post and black lead to negative post . Your reading should be 12-12.50 volts. If reading is low 9-10 volts then the final test would be a load test. You may have to go to your mechanic, or a battery dealer for this one because not everyone has a load tester. This test will tell you if you need a new battery. They will know right away. Your problem could be a bad battery. All the above tests are for DIY. If you are not able to perform these tests yourself then go to a battery dealer they will do tests for you. GOOD LUCK.

Try this, wait for the dark of night. Start your engine ,open your hood and look closely at the spark plug wires. If you see sparks jumping over and across the wires change the spark plug wires. They are probably old and worn. While your at it change your spark plugs. Your car should run one hundred times better after this small and easy repair. GOOD LUCK.

Relay # 4 is the fuel pump relay on your 1998 Jaguar XJ8L

Link HERE to see the actual picture of the trunk relay box.

Position # 4 is the center one.
1=bottom right relay (secondary fuel pump / SC only) 2=bottom middle rear window defroster relay
Label relay # and do a know good swap test.
Swap relay 2 to 4.
Please keep a clear record on what position and relay you are swapping.

It means your vehicle has an emissions or driveability fault code stored in the computer's memory. Fail safe will disable cruise control and possibly overdrive to prevent component damage. It also allows the vehicle to run on factory pre-programmed parameters so that you won't be stranded-depending on the problem.

All the lighting goes through the security module in the trunk. If both lamps are staying on them you probably need a new security module. If one light is staying on then you have cut the wire for that tail lamp coming out of the security module and jump the wire from the other tail lamp so both are powered on the one circuit.But first remove the lamp cluster, disconnect it and make sure you do have constant power going to the cluster. If so then first I would perform a hard reboot on the car. Disconnect both sides of the battery, wait for about 30 seconds and then join both of the DISCONNECTED BATTERY TERMINALS TOGETHER (this discharges any memory in the computers) Then reconnect the positive to the battery then the negative. Start the car, reset your clock and retest the lights. If you have the same issue then start with the wiring to the security module.

you hav to go out and do city driving and highway driving and get the monitors to say "Ready"

This is to prevent soemone with an emissions sytem failure from cheating by disconnecting the battery & clearing codes just before the test

fan motor faulty or temprature sensor faulty or wireing fault

Yes, you are correct, the brake light switch, at times called the microswitch on a Jaguar will cause the problem with your cruise control, as you have described. It resets and corrects itself with the ignition off, but once activated the fault will return. I hope this helps.

later model than mine but i think they will be individual ones on top of each plug ,take the plastic cover off and have a look ,then leave it off so the engine can run cooler

Unhooking the battery should clear out voltages in the system but I do not think it can reset the window controls. I believe the year you have does not store any memory. The issue could be in the control unit itself at the driver side. To be sure you may inspect the wiring by removing the door panel using screwdriver and rag to remove the screw and the rag and screwdriver to pry the panel out. You can directly connect the motor to the battery to test it. If it runs then it could be the wiring or the control unit. Check the wiring for loose connections or exposed conductors or terminals which has corrosion. Electric contact cleaner will help remove any dirt or corrosion.

The buttons you are referring to may be for the behavior of the window which lets it close all the way with one press or the lock of the window which turns off the windows except the driver side.

DID YOU RECONNECT IGNITION COILS AND THE VARIABLE VALVE TIMING SOLENOIDS.CHECK SPARK PLUGS IF YOU GETTING SPARK AT SPARK PLUGS.MORE LIKELY VALVE TIMING OFF.

yes, you can connect the negative cable anywhere on the engine and the positive cable to the starter or to the back nut on the alternator. Be careful not to let the positive jumper touch anything but the terminal.