QuestionQUESTION: Hi Howard. I have a 1984 Sovereign, Australian Delivered 4.2. I have had the car about 6 months and it has been well maintained by 1 previous owner. I last started the car about 1 month ago and it was starting & running good. I started it a week later and it started fine but was missing on 1 cylinder. As it hadn't been driven for a while & the plugs were looking very old I assumed new plugs were in order so I fitted new plugs. No start. I have read all of your posts and followed their advice over the last week, IE; drain & fill up fuel tanks, switch tanks for 30 secs, drained fuel from fuel rail, ( there was a little water evident.) Ran pump to get clean fuel through system, used 2 batteries, cranks well, all that jazz. the car fires on cold start but wont continue to run. Same when I crank and spray WD40 in intake. I Tested pump, OK. Going on what you have mentioned many times before about the ECU earths the injectors to pulse them, it seems the ECU isn't earthed as there is no clicking at the injectors. When I put fuel direct into the cylinders via sparkplug holes it runs until that fuel is burnt then dies again. My question is, (Yes there IS one)whereabouts is the ECU earthed? Is it under the rear seat as the only other work done on the vehicle in the last six months was a XJ40 rear seat fitted to the rear. Unlike the one that came out this seat is a full foam job so I'm wondering if it has damaged the earth? It was a hell of a job to get it in there so was wanting to rule this idea out without having to pull it out again. The car has run since the seat was fitted but I'm thinking maybe someone sitting on it may have done something as the foam fills all the available space. Thanks very much for your help Howard!
ANSWER: Hi Brad,
First confirm that you have power to the injectors with the key on and use a Noid light to confirm no pulse. The rear seat could very well be a cause of problem because the main harness goes under the rear seat and through into the trunk where the ECU is.
If you don't find something obvious you will need to start testing the pins of the ECU to see if the power supply is there and all the grounds are in fact grounds. You should not waste your time looking for harness ground points until you find out if that is the problem.
http://mg-tri-jag.net/XJ-6InJect1.jpg and change the end to /XJ-6InJect2.jpg for the other half.
I don't know if an Australian ser III is the same as a US version. You may be able to tell by looking at the injection diagram I have on my web site and compare it to the pins on your ECU.
Check the power supply and the several grounds and the ignition pulse signal from the coil. The diagram is in two sections so you will have to copy and print both and put them together. Follow the diagram and the pin numbers on the ECU plug.
Pin 1 is the ign signal
Pin 5, 16, 17 %26 35 are grounds
Pin 10 is power in
Pin 4 is power in the start position
Everything else just changes fuel mixture other than the injectors pulsing grounds (14,15,30,31,32 %2633)
Howard
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1974 Leyland P 76
QUESTION: Hi Howard, Thank you for the very quick response. I shall try the pins as you suggest. I have the ECU carpetted cover off in the trunk and could see the loom enters there hence my guess about the seat. I will pull the seat out and try there first. I'm not familiar with a Noid light, they may be called something different here, like we call the trunk the boot, or Gas petrol, or Bush nuts.....actually scrub that last- he's not here to defend himself. So I'll investigate. I did try putting a test light on some of the injectors with ignition switched on and it glowed, so I assume there's power there. As mentioned the car does run if I add fuel via spark plug hole and the problem is definately on ALL injectors so this is the sort of logic thats got me this far: All would be unlikely to fail at once so must be something they all share, there's fuel being pumped Right Up To the injectors but not reaching the cylinder but it fires when I put some in there so my compression & spark & battery are all good so my assumption is the pulse or lack of is the issue. I'm hoping the new seat may have stretched the earth wire and broken or removed it. I will let you know the outcome. Hope my logic makes sense...As for the Aussie Jags being like US ones, I think apart from the steering wheel on the Right hand side and the headlights changed, (L to R for dipping) they're the same. Certainly the same as a Jag bought in Britain anyway. It does have a plate on the RHS inner guard that says 'FEDERAL'. Haven't been able to find what this may mean anywhere on the Net but Federal cars are mentioned in the Haynes manual but not in a descriptive context. Do you know what it means?? My car has Australian Compliance plates dated for the build date saying it was built by JRA. ( Jaguar Rover Australia ) I believe they assembled Jags, Rovers and Range Rovers here in the 80's but stand to be corrected. There was certainly some wretched cars built here woefully by Leyland in the 70's. Marques ruined included Rootes, Rover, Landrover, Morris, Leylands and Mini's to name a few. On the other hand there was the startlingly good Range Rover 3.5 V8 powered P76 - a large Australian designed & built sedan around the size of a Crown Vic. Picture added. Sadly it came into production within 12 months of the collapse of a hopelessly ineptly run Leyland Australia. Sorry for going off topic but I thought given your background you might like to hear what happened down under. Cheers! Brad.
AnswerA Noid light is a small light that plugs into the injection harness to test for an injection pulse. Most auto parts stores here have them. There are several different ones for all of the injection systems so you would need to ask for the one that fits Bosch/Lucas. They are very inexpensive here.
The "Federal" refers to the car meets Federal Emission standards which here means US Federal standards. There are two standards here, Federal and Calif. California has tighter restrictions for emissions.
Your logic is good including "Bush / nut". Generally the ECU needs power and several grounds and it needs to see an ignition pulse signal to start doing anything. It grounds the injectors in groups and two times per cycle but is not timed to inject just when the intake valve is open. All of the external sensors tell the ECU how much to change pulse duration (mixture) Some are major and some minor influences like the airflow meter and the coolant temp sensors are major. The cold start injector is not controlled by the ECU. It is activated by the start switch and controlled as for time that it is on by the thermal-time switch in the coolant rail. In place of an accelerator pump used in a carburetor, the system uses the lack of vacuum on the fuel pressure regulator to boost fuel pressure when the throttle is opened. An additional item to richen fuel mixture at full throttle is the throttle position sensor (just a on/off switch)(when this Bosch injection system was used on other cars it was a true throttle position sensor)
By removing the ECU and plug you should be able to see small numbers on the pin positions to ID each pin socket and with the diagram you can test each important circuit as I listed. The ECU is expensive so you may need to check that each pin socket in the harness goes where it is suppose to go and not shorted and has power when it is suppose to and that there is a ignition pulse signal etc. A lot of work when an extra ECU is not available but needs to be done.
Most shops keep a known good ECU for quick testing of a dead car. I only had to go down the list of pins once in a shop where I didn't have an extra good ECU.
I don't work on other people's cars any more but I do have two XJ-6s of my own and I have to keep an extra ECU for testing. Oddly enough, in working on injected Jags for 30 years I only ran across two bad ECUs, one on a car I was working on and one on a car in a shop of a mechanic that attended one of the seminars I gave traveling the whole US for Beck Arnley/World Parts corp. Even though it is the most complicated high tech part on the car it is also the most durable. My hat is off to Bosch for that.
Your car looks great, what does the front look like?
Howard
