Hello everyone,

Among the many issues of my 1988 XJ40 Vanden Plas are the central locking and the fuel door. I have to use the emergency release in the trunk to open it, and although I have read many different threads online about it, none of them seemed to work. I do know that the 1988 model year uses something related to the central locking and has a solenoid and PCB behind the carpeting in the trunk, but I don't know what to do despite knowing this knowledge. Finally, the central locking in the rear seems to lock but not unlock without manually pulling each individual pin up. Can anyone help me? Thanks!

 

Hi wpaturzo,

Problems with central locking can be time-consuming to diagnose because they can be caused by a combination of electrical, electronic, and mechanical malfunctions.

A common issue is that the lock linkages in the doors seize up and need to be lubricated and sometimes adjusted, then exercised untill they move freely again. There are some threaded plastic fittings that connect metal rods, and these plastic fittings can break.

The plastic door top trim panels tend to distort with age, causing the chrome-plated plastic ferrules around the door lock posts to tilt and bind. Sometimes lubricating the inside of the ferrules with white lithium grease will help. If not, try removing the ferrule to see if lock operation improves.

The lubricant in the small gear motors in the power lock actuators dries up over time and unless the motor has become corroded, it may be possible to resuscitate the motor with cleaning and lubrication.

The locks are operated by the Door Lock Control Unit in conjuction with the Central Microprocessor (CPU), both of which are behind the right hand knee bolster and glove box. A known issue is water damage to the CPU due to clogged drains that allow water to pool below the A/C evaporator in the center column and to slosh onto the CPU when cornering to the left.

The fuel filler flap actuator solenoids are known to fail, but check the fuel filler flap relay, which is behind the left trunk carpeted trim panel, near the fuel filler box assembly.

I hate to say it, but you may have to go through the entire system to restore proper operation. You can download the Electrical Guide at this link:

Jaguar XJ40 Electrical Guide 1988-1989

I'm sure I've forgotten something - hopefully others will fill in the blanks.

Cheers,

Don