I have a 1990 XJS V12. Was running great. Drove it about 10 miles shut it down, came back 1 hour later, started ok but noticed a little rough. Got out on the road and no power. Degraded as I drove it. Drove 2 miles, parked it shut it down for half hour. Restarted, very rough idle, no acceleration bogs, a bit of popping, back to rough idle. At the time there was a lot of smoke, appeared to be center of engine, but hard to tell. Let car sit for one day, tried again, same thing accept no smoke this time. Got a flatbed to get it back to my garage. Will be most interested in any thoughts / ideas..... Thanks for reading!

 

Welcome to the forum Woodrun,

I've moved your question from General Tech Help to XJS forum. Members here with the same model will be able to help.

Please follow this link New Member Area - Intro a MUST - Jaguar Forums - Jaguar Enthusiasts Forum to the New Member Area - Intro a MUST forum and post some information about yourself and your vehicle for all members to see. In return you'll get a proper welcome and some useful advice about posting to the forum.

Graham

 

Hi Woodrun

Could be Fuel Starvation, Blocked Fuel Filter and or Fuel Pump on the way out, very easy to check out and not too expensive to change

If you need to buy a New Pump there are Generic ones on ebay for about £30 (UK) and a New Fuel Filter is about £10 (UK)

Changing both if you need to is a 'Walk in the Park' but if you do then also clean out the Sump Tank which is underneath the Battery but be sure to DISCONNECT THE BATTERY FIRST!

Also don't go pulling hoses off as the Fuel Pump and Sump Tank are Gravity Fed from the Main Tank or you could have Petrol Flooding Out Everywhere and if you clean out the Sump Tank then also change that filter which is under the round lid

Always use a Wooden drift and a Rubber Hammer to knock the locking ring round if you don't have the special tool for the job, so that you don't get any Sparks and do the job outside not in your Garage

Having said that it also may be neither one of those things and could just as easily be a leaking diaphragm in the FPR
(Fuel Pressure Regulator)

Which will be the one on 'B' Bank which is on the same side as the Oil Filler Cap, where in order to see if its working Ok it really would be preferable if you could get a 'Shop' to Test the Fuel Pressure in the Rail

The list goes on............

 

Orange Blossom...could it also be the dreaded Marrelli Ignition Rotor shorting out on the distributor shaft? I will be checking mine tomorrow on my new 90 I just purchased.

 

Thanks guys! Really appreciate the quick response. I will start tearing into over the weekend and report back.

 

Hi Guys. last you heard from me I had a rough idle no power. I did the following.
Replaced distributer and rotor (had the parts so figured why not) no change
Removed sump and did full clean out - it was not that bad, but the car ran great once put back together. Took it out for a ride, died 1 mile out. Towed it back to garage. Replaced fuel pressure regulator as it was clearly leaking back through along with fuel lines. Car ran great! Took it out for a ride, died 1 mile out. Towed it back to garage.
I kind of have a feeling it will start and run fine when I get to the garage tomorrow. If so, I am thinking something like the coil is going open on me. There is no start at all when this happens. Engine turns over fine, but no start. Will report back tomorrow as to whether it starts and runs fine cold. Open to any thoughts.

 

Replace both crank sensors for sure, and then amplifiers and then the coils, one at a time until it is fixed, is what I would do if funds allow.

 

Hello Greg,

Thank you for the feedback. Your reply makes sense to me. I will get on this over the weekend. I was not aware of 2 CPS?

By the way, I used to spend time in CAEN. Loved it and miss it!

 

I've attached some Jag literature that has good info on the Marelli ignition, crank sensors, and so forth

Cheers
DD

 

Thank you Doug! Great info!

Had all the manuals on my laptop which I left on a plane earlier this week. Hoping to get it back, but with each day that goes by the chances lessen.

 

Change the ignition amps at the end... Not before the coils. The amps cost a fortune. The coils are cheap. Any generic coil as per Marelli setup is sufficient.

The sensors tend to lose their magnetic fields with time, so the readings can be bad. Make sure to first clean them up, refit and check the gap afterwards. I haven't got the figure in my head but the gas is inportant. The front sensor is probably the most inportant one for the Marelli as it is Marelli specific.

When it bogs out, check and see if you can identify if you are receiving any sparks. A friend of mine had some issues on his 91 Marelli, where as once warm, the ICU would switch off supply until it cooled down. He opened the ICU and found some broken contacts. Resoldered them and it works a charme...

 

What is the ICU? (Do you mean the ECU main computer?)

 

noooo, if I meant ECU I'd write ECU ICU is the Ignition Control Unit. An extra little CU under the dash only for the ignition system

 

Hello everyone,
was just wondering if someone knows where that ICU unit is located in my british car (steering wheel on the right) and what sort of size is it and how does it look like,
I noticed a bit of water ingress at the left near the fuel cut off switch next to the left door, is it somewhere there, maybe thats why my car is running with extremely low power since driving it through the car wash, some water might have got in somewhere, or maybe its just a coincidence, it was running a bit low on fuel at the time as well, but i changed the small sock filter in the small tank already, cleaned out the small tank, and changed the other fuel filter, but its not making any difference....

 

Just wanted to add that IF it is ignition, you can get very good and cost effective marelli modules for about $30/ea when I bought a set it was about that. No need to sell a kidney for genuine marelli units.

VE520225 Cambiare ignition modules work perfectly.

 

ok thanks, but is that the ICU under the dashboard, or somewhere in the engine bay, and how can I get to it and how can I test it?
If its under the dashboard, my car has the steering wheel on the right side of the car....

 

Follow the tiny red vac line. It should be up behind a footwell panel on the door side, 4 screws at most. No idea on how to test a unit, thats beyond my abilities.