With further testing, I do have +12V at the power modules and the coils. I was also thinking that the +12V split for the ECUs could also be in the trunk since that is where the +12V source is, the battery.
Paul
Not unless there’s a relay, since that 12V power is controlled by the ignition switch. However, the power for the EFI ECU is controlled by a relay. So it depends on whether we’re talking about the actual power to the EFI ECU, which comes from battery to relay to ECU, or the power to the relay, which comes from battery to ign switch to relay.
Hi Kirbert,
Let’s look at this another way. From my further testing, there is a central distribution point shown by the red arrow. That point comes from the ignition switch and from there gets distributed. Where ever that point is there is a single wire that goes from that point to several points showing in the digital ignition diagram.
If I had the wire color coding and knew where that point is, I could trouble shoot the one lead that goes from there to the ignition ECU. If need be I could splice in a new wire and go on from there, +12V to ign ECU solved or more specifically, remedied.
So I take you do have power at the coils?
I’m still not convinced the wiring actually branches the way it is shown. The amps and the coils are in the engine comparment while the ECU is in the passenger footwell. It would not make sense to route a lead to the engine compartment and then branch off a lead back into the passenger compartment. It also would not make sense to have one lead from the ignition switch to the passenger footwell, and four separate leads branching off from there to the engine comparment. It would not surprise me in the slightest if the actual junction point is right behind the ign switch, possibly at that coupling where the short leads from the ign switch plug into a harness behind the dashboard.
Hi Kirbert,
Yes I do have +12V everywhere on the ignition system except for the ECU. I’m going to re-check pin 13 this morning and then probably break open the connector to check that out and also find out what wire and color coding supplies the +12V.
Then I can further trace the +12V or just splice in a new +12V wire/source to power the ECU. It’s all a question of how easy it will be to trace the +12V supply wire. Breaking open huge long lengths of harness bundles is not going to be a choice.
Paul
Update!
This morning I got +12V on pin 13. Checked and double checked. Just have to ‘chalk it up’ as ‘due to further clean-up after the fact’.
I have now gone further and can see that I have definite clear continuity at ECU inputs 1 & 2 and 3 & 16, the inputs for TDC sensor and engine speed.
I’m writing this as I contemplate what next to check out.
Paul
Paul,
I sent you pictures of the “Symbols” page (ii) and “Wiring Color Code” page (iii) from my hard copy S57 Electrical Guide via PM about a week ago. You must not have seen that or the follow up PM that I sent. For some reason you said that those pages weren’t included in your downloaded digital copy.
The wiring color codes that Jaguar used are also found in various Jaguar documents including on page 145 of the XJ-S Repair Operations Manual (ROM). If you don’t have a hard copy of the ROM they are available for less than $100 on eBay for a new one, and about $50 for a used copy when they show up. I can’t imagine working on the complexities of the Marelli Digital Ignition or Lucas Electronic Fuel Injection system in our 1990 XJ-S convertible myself without the XJ-S ROM to refer to. Having the proper technical data has removed a lot of the mystery of working on these cars for me.
You are wondering about the wiring in Figure 30.1 “Digital Ignition” of the S57 Electrical Guide. If you look at Figure 1.1 “Harness Layout -Connector Locations” you will see that connector CF6 is located in the engine bay at the rear. It is a big round black plastic connector with just a few wires located beneath the Balance Pipe. I suspect that Kirby is correct about the location of those branching White wires and they might be inside the dash somewhere.
Just in case you don’t have the XJ-S ROM or can find the PM that I sent to you, here are the Wiring Color Codes: Brown (N), Black (B), White (W), Pink (K), Green (G), Red ®, Yellow (Y), Orange (O), Slate (S), Light (L), Blue (U), Purple §. They are sometimes used together light LGS for Light Green with a Slate (Grey) trace.
Paul
Paul,
For some reason the email version of my most came out with unechecked changes to the Red an Purple color codes, perhaps because I used parentheses. The online version is correct showing Red is a capital letter R and Purple is a capital letter P.
Paul
HI Paul,
I don’t know why but I never saw your addendum emails. Please resend. I will keep a particularly sharp eye out for them.
Thanks, Paul
Oh Happy Daze! Hallelujah! Got a spark and the injectors are clicking. Now to put pack together the various little do-hickies, get the engine running and on the 'road again!’
Paul
Paul,
I have been following this discussion with great interest because I too have no spark on either bank.
I have not done as much exploring as Ptipon has as I really didn’t know where to start. I can hear the fuel pump run but no power at either plug at the coils. That’s about as far as I’ve gotten. I didn’t know where to find the ECU and still am not sure exactly where it is. Took off the panel on the left side of the passenger foot-well and below the glove box. I have power at the 2 30 amp fuses located there.
Anyway, could you also send me the same information you sent Ptipon? It would be a great help.
In the mean time I’ll be exploring the items you have discussed in this amazing thread here.
I have found both the S57 Electrical Guide, the XJS repair manual and the parts catalogue on E-bay and will be ordering those today. But I’m hoping to get it running by this weekend for our big car show here in McGregor, Mn. My e-mail is patmccart@yahoo.com
1990 XJS convertible with the 5.3 V12.
Thank You, you both have been a great help already.
Pat
Paul,
I resent the pictures that I took of pages II and III from my S57 Electrical Guide last night via PM. Please check your email inbox and confirm that you received them this time. If they are not in your inbox please check your spam folder.
Paul
Pat,
I sent you a PM with pictures of pages “ii” and “iii” from my hard copy of the XJ-S S57 Electrical Guide. They should be in the copy that you ordered, but in case they are not you will have them.
The Marelli ignition ECU is located in the right front corner of the right side passengers footwell. Remove the carpet and you will see the cover. Remove the bolts holding the cover on and you will find the Marelli ignition ECU.
These cars are complicated and I have learned that when something doesn’t work right it is necessary for me to have the right technical data, like the XJ-S ROM, the S57 Electrical Guide, the XJ-SParts Catalogue, Kirby Palm’s excellent “Experience in a Book” as well as the Driver’s Handbook to help remove a lot of the mystery (but not all the mystery) from working on these cars. I do not believe that these cars can be properly maintained through emails alone.
Paul
Thanks Paul,
I took all the info I got from this thread and was going to go through each item one by one.
Started with the Crank Senor plug, it was a little corroded, cleaned it up and added some electrolytic grease and POW it started right up.
Glad that’s all it was. Also glad to have learned so much through this forum.
Opened up the area where the ECU is just to find what condition everything was in and it all looks like new.
I’m very lucky.
Thanks again everyone.
Pat,
Congratulations on getting your car running. Often the source of the problems are simple and inexpensive to fix. Look at the simple stuff first before going on to the harder stuff.
Did you receive the PM with the attachments?
Paul
Hi Pat,
Glad to hear it’s all solved and running. I didn’t have time to get back to you, I work 9-5. I was going to suggest doing what you did. That’s all I did and got things running again.
I recommend Chem tool to clean the grease, then contact cleaner to clean the contacts and finally dielectric grease to keep it all clean, dry and non-corroded. It worked for me.
I got home tonight after work finished up the final touches and it started right up after about 5-10 sec for the fuel the pressure up. Nice and smooth. My Jag has always run very smoothly, so smoothly one has to look at the tach to know the car is actually running when I’m stopped at an intersection.
Paul
Hi Paul,
Been watching all of your posts yesterday and all day today and I see no pictures at all. Did you send thru Jag-Lovers or to my email??? But I don’t see them at my email either.
Paul
Paul,
I sent the pictures to you via a Jag-Lovers PM. This has worked for me successfully dozens of times so I suspect that the problem may he on your end. Do you have a spam filter or spam folder? Sometimes those filters are too generous.
Paul
Paul,
Yes I got them.
Thank you very much,
Pat