I own a 1989 XJS 5.3 Sports Coupe vin: SAJJNAEW3BB163544

Engine will not start and run
Sequence of events:

My car has Marelli digital ignition.

A few weeks ago my car started running on 6 cylinders only. i.e. the right hand ‘A’ side of the engine. I found the vacuum line that runs from the distributer to the Air Filter on the ‘B’ side of the engine had failed. I fixed that problem and at the same time put a new rubber connection to the top of AAV as it was also cracked.

I then decided to renew my Spark Plugs,Ignition Leads,both Coils,Distibuter Cap and Rotor Arm. After I put it all back together The car started and ran like a sewing machine for about 10 minutes, then it stopped dead. I later managed to start it but it only ran for about 20 seconds.

I had read in the ‘Experience in a Book’ XJ-S help that this is sometimes caused by a faulty fuel pump which can work intermittently. I decided to buy a new Fuel pump and Fuel filter as the car is over 20 years old. I installed both today and the car started and ran for about 5 seconds then died. The new fuel pump seems to be running ok . Is there a way of checking if the spark is ok and if petrol is getting to the Injectors? I am now at a loss what to do and my nearest Jaguar garage is about 30 miles away.

 

First I would be checking the work you have done. Make sure the plug leads go to the correct plug and that the 2 coil leads are connected to the correct terminal on the dissy.

Firing order1A 6B 5A 2B 3A 4B 6A 1B 2A 5B 4A 3B

To confuse things the ignition module on the LH side of the car runs the A bank

 

Thanks Warren, The ignition must have been ok for the car to run perfectly for 10 minutes. The problem is after 10 minutes it suddenly stopped dead. There was plenty petrol in the tank. Maybe it is a blokage nearer the engine or something happened to the electrics. It is a mystery. I took of the connection at the fuel filter in the boot and tested the pump, it was working fine. Do you know if ther is another fuel filter on the engine? When I turn on the ignition there is a clicking sound coming from the engine area?

 

The only fuel filter is in the boot, unless someone has installed another one. The clicking sound under the hood will be the ABS pump.

Sorry I misunderstood what you meant. I would check the fuel pressure at the rail it could be a slow pump, clogged filter or bad pressure regulator. Just read you have already replaced the pump. Check the regulator.

 

when i had a bad injector on my L67, i lifted the fuel rail up about an inch, and started the car. found a dead injector. *risk of fire*
you could probably do the same thing with the V12, but i would reccomend a mechanics stethoscope first. the injectors make a clicking sound when theyre working. if ones not making any noise, then its dead.

but that wouldnt tell you much in the way of fuel pressure. you could have good injectors and no FP.

 

Since there is no schrader valve or other fitting on the XJS to check fuel pressure at the rail, the place to do a pressure check is on the left side past the fuel regulator valve on the hose going to the left rail. You have to cut the rubber hose and install a T fitting to be able to attach a fuel pressure gauge. Your choice on what to do with the cut hose after....I replaced the hose after I had completed all my work on the fuel system, but you could install a schrader for future use since they are available for this application.
The pressure should read 32 to 33 psi at this point...if I remember correctly.

 

To test for spark at each plug, there are many spark testers available from $5 up at any auto parts store. A good item to have in your tool box for anyone. This will allow you to know for sure if you have an A bank B bank issue or if one or more is not getting fire to the plug without doing much more than removing the plug wire and inserting the spark tester on each plug.