So after having my mechanic diagnose the issues on my 1992 XJS 5.3 V12, which wouldn't start or crank, he finally was able to get the engine started independently but no fuel is going into the engine.

About a week ago he told me the issue was likely the TPS so I went and purchased a new TPS and that didn't do the trick. He is now saying that the issue must be the ECM/ECU since the fuel injectors are not showing a positive and a negative output from the ECU therefore not causing them to work. I may have misunderstood him but that's what I remember him saying.

He's saying in order to get the engine running fine, I will need a new ECM/ECU. From what I noticed, the injectors are getting power when he tests them with a voltage meter, all of the other lights and switches work on the car and the engine cranks.

My questions is, does it make sense for me to go purchase a used ECU

(I only found one online) 1992 Jaguar XJS 5 3L V12 ECU ECM Engine Computer DAC9619 | eBay

or does it make sense for me to just go ahead and replace the entire system with a new ECU and new EDIS system.

I was thinking of replacing the Marelli distributor system anyways with a more updated EDIS system. If I do that won't I need an new ECU anyways or can the Lucas ECU control a new EDIS system? If that's not the case doesn't it just make sense to purchase a new ECU now and get rid of that awful ignition system that tends to cause fires?

If that's what makes the most sense, what is the most cost effective EDIS system and ECU set up and what are all the parts I would need to purchase so I can run it by my mechanic. What's the budget for something like this?

Or does it just make sense to listen to my mechanic and purchase a used/new ECU to get her up and running? Again, I will eventually be looking to replace the distributor system to a Electrical Distributorless Ignition System.

I've read a lot here on this forum but I am a newbie as this is my first restoration car and first jaguar, so I kind of need someone to spell it out for me as simple as possible.

From what I've read, and researched the twin Ford EDIS system is the most effective and cheapest correct? Here is a video.
Any help is appreciated!! My mechanic so far looks trustworthy but I'd rather be educated on what I can do before I speak to him so I can know what all my options are before he makes his own suggestions.

Thanks!!

 

OK, it looks like you from "no crank, no start" to "cranks but won't start". Is that correct? What was done to get to this stage?







It's plausible the the ECU is at fault, yes. In that case replacing it with the realtively inexpensive Ebay item seems like a good idea.





If the fault has been correctly isolated to the fuel injection ECU then it makes no sense, IMHO, to replace the entire system.

The "correctly isolated" part is important here.






Just for the record it is possible to be free of fire with the Marelli system. Just takes some regualr servicing, a dab of silicone, and periodic inspection of the system.






It sounds like, in your heart, you really want to do these upgrades/changes. If that's what you want, go for it! In so doing you'll probably fix the no-start condition along the way.

If you simply want to restore your XJS to running condition then replacing the ECU sounds like the best plan.....if indeed the ECU is at fault. Lack of injector pulse could be a number of things which, from what you've mentioned so far, we don't know if the mechanic has checked.

Cheers
DD

 

Well, according to the mechanic he was able to track down another ECU to try it out on my car and that didn't do the trick.

Going into the shop tomorrow to chat with him but he's telling me that he's stumped and might have to refer me to another mechanic since his shop is too busy to keep tinkering.

We'll see what happens. Not sure what to do now if this guy states he can't get to the bottom of it.

I have two other mechanics in mind. One is a family friend who'll work on the car and charge me as he goes, another is someone who I found on the net and works at a dealership but does side work.

Wish me plenty of luck! lol

 

If the car will start on ether squirted in the intakes, then it is a fuel problem. You car has two position sensors, one on the crank pulley area and one on the flywheel. It is both cheap and sensible to renew both of these to start with. I have no experience of the Marelli system, but I have a feeling the fuel side of things needs to know the engine is turning.

Then be absolutely SURE the car is getting fuel to the rail and that the pump is working as it should. There should be about 30/35 psi at the rail.

If all this is done and still no start, AND your guy is 100% sure the injectors are not pulsing, then there are guys on here who can suggest diagnostic procedures. Why not post again, having done all this, before doing anything else drastic? Installing a whole new aftermarket system is a very long and difficult thing to do on an XJS V12; getting it running well once done, is even more difficult.

Greg

 

Hey fellas! Thanks for the help. ECU was replaced and it did the trick. Car starts up like a charm!

Now on to the next project. My mechanic is saying that the entire exhaust system should be replaced.

Here is the list of what he told me to buy.

4 Catalytic Converters. 2 front 2 rear
2 Center pipes
2 Center mufflers
2 Over the axle pipes
2 rear resonators

He told me that it's best if I buy the complete exhuast system all put together. I'm pretty sure it's so all he has to do is install it.

I understand that this is probably easier so he doesn't have to weld anything etc.

My question is where can I find these and what are the cheapest and most efficient. Can I buy performance parts that are direct fits with each other as I was hoping to get magnaflows etc.

If that's not utterly necessary are the Universal magnaflow catalytic converters and mufflers any good?

Thanks in advance.

 

Badkat174,

Without wishing to criticise your mechanic, does he really know much about these cars?

I've never seen an XJS that needed the whole exhaust system replacing in one go including downpipes and catalytic converters unless it's been sitting in a wet field for 10 years. If it needs all that he says it does, I hope you've got deep pockets!

You don't buy the system fully built up. I have no idea why he said that! It would be impossible to fit to the car like that! All the sections bolt together, there is no welding required to fit the exhaust.

Just a suggestion but I'd be looking for a new mechanic.

Good luck with the exhaust.

Paul

 

Hey man, thanks for the reply. He was recommended to me as a good mechanic and he was able to figure out a bunch of things in the engine to get the car running.

Every time I go into his shop he's had a few jaguars sitting around and I saw about to other XJS's so from what I understand he specializes in these cars but it doesn't mean that he knows much about the exhaust system.

He's letting me purchase all the parts myself so he's not making any money off the parts however I do question needing to replace everything.

I've been looking around and it looks expensive as f*K!! Pardon my french haha

Some of the parts of the exhaust look rotted out and the catalytic converter blew the last time I used it but not sure if the entire system needs to be replaced as he says.

Hopefully this isn't the case but I'm looking into maybe getting a second opinion.

I found this custom kit online and I was wondering if I should just find a muffler shop that can duplicate this.

XJS GT Stainless Steel Sport Exhaust System