My ecu is broken on my 85 v12 XJS. I purchased a 16cu off eBay and it is completely inoperable. Does anyone know how to either fix the 16cu or know of a source that isnt trying to rape you on prices? A local place here in Atlanta, GA wanted $400 for the older ecu and I don’t really trust eBay anymore. Any help or direction would be appreciated.
The only repair source I’m aware (that is, one who knows Jag stuff specifically) is Roger Bywater at:
He’s getting up in years; last ECU I sent him took 2-3 months to get back. But, he’s the expert.
Cheers
DD
It’s been reported that you can often fix these ECU’s yourself by simply opening them up and replacing every electrolytic capacitor you can find.
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A very generous forum member sent me a 16cu and it didn’t work. So far the 6cu holds the left bank open solidly, the first 16cu only fired the right side and the latest 16cu sent to me doesn’t fire anything at all. I am very very close to doing a swap for an American v8. As a purist at heart it pains me but I am no longer going to torture myself with weeks of waiting for expensive ecus just to be let down. This car is in way too good of shape to just junk.
Hi Adam-
So is the conclusion that all of those ECUs are in some way bad?
Is the 16cu you received from the forum member supposed to be good?
You can see where I am going… are you sure this is an ECU problem?
(I am not saying that I have any idea what besides the ECU would cause these symptoms, just asking questions…)
Regards
Bob
Where are you located? I have a 6CU of unknown function; I could try it in my car, and if good, you could try it.
The one from the forum member was questionable whether it functioned or not. They all display different symptoms. I have tested everything else a few times. All of the wiring, the electrical, continuity, everything else I could think of. Everything tested fine.
I’m located in Atlanta, GA. Where are you located? I would love that!
I am in Michigan, my kid lives in Atlanta, not that it helps (he is up here like once a year). I’ll try it tomorrow, and let you know.
Thank you so much. Would be willing to sell it if it works?
I’m sure we can work something out.
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Sounds good. Let me know when you find out if it works.
No good on the 6CU ECM; I plugged it into my V12, it fired right up, fuel pump working, but low idle. Died after about 15 seconds, and fuel pump stayed running. Tried to start, obviously running too rich. Looked under car and liquid fuel running out of right converter.
Plugged in the original ECM and was able to start and un-flood. Took about a half hour for the right exhaust to stop blowing white smoke.
So, “A” bank injectors driver circuit is grounded. Pulled the covers on the 6CU ECM, but unable to remove boards to see injector switching components, which would be a likely fault area. Both the logic and switching boards are mounted trace side outward, so you can’t see components.
Sorry, sounds like a common failure mode. Look for a 16CU.
Coventry West isn’t far from Atlanta; check with Dick Maury, he may have an idea we’re you could get an ECM to try.
Thank you so much for checking that. This forum has really been so super helpful. I believe this forum to have the best, most helpful members of any forum I’m part of. . No go on the 16cu. Tried that twice and Coventry West is part of the reason that I am going to go ahead with a v8 swap. They wanted close to $500 for a 6cu. That’s just plain robbery. I always said about myself that I am not a quitter but I’m smart enough to know when to stop trying.
Including yours and mine that’s 4 ECUs that are disfunctional. I don’t want to deal with any of that in the future. As much as I wanted to keep this thing original I know when to stop trying.
Personally, I wouldn’t lump it- look into Megasquirt, there are already Jaguar V12s running it. From the little I know, they offer ECM kits ($250?) as well as built units at less than a used Jaguar ECM. I think it will run with all the OE sensors, and allows upgrading the ignition to wasted spark.
That’s what I would do.
The problem with that route is the fact that I don’t know if this thing will run right or even move. $2500 on a mega squirt that I could get stuck with. Would be a vastly different story if I had been driving her already.
Out of curiosity, why would you not lump it?
Because its a V12 Jaguar.
That’s a brilliant response. Thank you so much.
Adam, I am not sure how quickly you want to proceed, but maybe while you explore the lump option you send the 16cu to Roger Bywater and get it fixed. When it gets back you have a known good ECU, you try it, maybe the car runs good and you like it, maybe not. If not it seems like you could sell the ECU for at least close to the cost of what it cost to repair it, (guessing $500?) especially if you get his “super enhanced” upgrade. Somebody will buy it. Just another thought.
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This is the type of constructive advice that I appreciate. I started to look into getting the ecu repaired. I’m struggling with the amount of time that would be required to get it back from England. Does anyone know his turn around time and cost for repair?