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Paul, Alex
On the V12s the starter relay does give a signal to the ECU thazt the engine is cranking. Maybe the line concerning the AJ16 is in there by mistake? Or maybe not!
Seer the attached diagram for the Lucas V12, bottom line, first right after the centre.
Greg,
That V12 pinout is interesting, as it doesn't overtly mention the V12 CPS? Unless it's an oblique reference on Pin 18? I might dig out the V12 wiring diagrams and try and also understand that Starter Relay signal vs CPS signal.
As much in the interest in helping OB as improving my own understanding(!) I've pored over the wiring diagrams for the AJ16 to try and clearly interpret all the signals in and out which control the Fuel Pump Relay.
Unless I'm misreading something (or the diagram is wrong), there does not seem to be any input signal to the ecu from the Starter Relay, despite what the other Jaguar documentation implied.
The Fuel Pump Relay energiser circuit links a feed from the EMS Power Relay and an output signal from the ecu. And the only really relevant input signal to the ecu that might indicate a cranking condition seems to the signal from the CPS (as I expected).
So, at the moment, I'm still hanging on to my belief that on an AJ16, the Fuel Pump Relay requires a signal from the ecu which is triggered by an input signal from the CPS. If anyone can find a wiring diagram that shows an input from the Starter Relay to the ecu, it would be really helpful.
This may sound like Twisted Logic but I'm thinking that the CPS is Failing, rather than Completely Failed
As Yesterday the Engine Fired but only for One Second
So I think that on Balance I'd rather Spend a few Sovs on a New CPS to find out if the CPS the problem
OB,
Yes, the CPS does seem to be a law unto itself at times, so I understand your reasoning.
Also, just to clarify, a full throttle position whilst cranking also cuts the fuel circuit, so it's a good way of clearing flooding. Gradually, the engine will then start to stutter from the residual fuel as it's cleared. And then you can start to bring your foot off and let the fuel circuit re-engage. I've only had to use that technique on a few occasions when I inadvertently turned off the engine after initially starting, and the rich fuelling conditions meant that it then found it difficult to restart. It's why you should never turn off an AJ16 directly after a start until it's started to lean out a bit, or ideally, fully warm.
I should hopefully understand all that much better in the daylight when I am with the Car
Since you mentioned the Starter Relay, please could you tell me where I can find that, as maybe I might discover an obvious fault
I've also found the Relays for the ECU that are DAC 7686 though I seem to remember reading about a Service Update where they recommend you swap these out for JA-LHF 6703 AA
These are above the Fuses behind the Passenger Side Knee Panel there are two of these but they don't say what the other one is for or even which one is the Relay for the ECU although one of them must be?
OB,
They are both involved in the "ecu" operation.
The one with the white base is referred to as the "EMS Power Relay".
The one with the blue base is referred to as the "ECM Controlled Relay".
Essentially, you need them both! The one that links the energiser circuit from the ecu to ultimately trigger the Fuel Pump Relay is the "EMS Power Relay".
Also, I don't think you can have a problem with the Starter Relay if the engine is cranking but it's in the group of 3 at the right front of the engine - Blue with a White base.
It occurs to me, the problem here is quite simple, Alex:
The car does Not want to leave your company!
It's been Happy with you all these years.
As far as it's concerned, you two are Bonded!
As I have been thinking exactly the same thing but as nice as She is She is not my Favorite Car!
Quite possibly because I would be just so careful with her, that I would end up by not enjoying the drive
So not for nothing have I always called her 'Granny's China' only to be taken out on very special occasions, so now She is getting her own back by refusing to Start, so hopefully she will be going to someone not so Paranoid or as Sentimental as me!
Ah yes, of course, the pre-CPS Lucas system. Schoolboy error!
I'm struggling to see why you'd need a signal from the Starter Relay if you have a CPS, so am still slightly confused by the statement in Jaguar's staff training material for OBD I / II
EMS systems (4.0 & V12) where it says that the ECM receives a signal from the Starter Relay when cranking. I think it's a hangover from the Lucas engine spec and is an error.
EMS systems (4.0 & V12) where it says that the ECM receives a signal from the Starter Relay when cranking. I think it's a hangover from the Lucas engine spec and is an error.
Paul
Just what I thought too Paul, but what with the desperate complications on how the facelifts' electronics startup systems work, that you and Ferrari guy have so knowledgeably written about, I dared not suggest it!
Trying To Start My 1995 XJS Celebration Convertible
New Crank Sensor Arrived This Morning
But Did That Make Any Difference?
Ordered My New Crank Sensor Last Night and it Arrived this Morning!
Though as I was up early I thought I would do a resistance Test on My Original CPS as well as the one I replaced it with a Couple of Years ago and then Compare that with the New one that was due to arrive this Thursday but instead Turned up To-Day! (Customer Service On Another Level!)
So here is what I found, as according to what I'd been reading Resistance should be somewhere around 800 - 1000 Ohms
Original Lucas Crank Sensor that was on the Car when I bought Her 1.367 Ohms
Replacement After Market Crank Sensor from 2 Years ago 1.467 Ohms
New Aftermarket Crank Sensor that Arrived This Morning 1.347 Ohms
Conclusion: All in Spec although any reading less than 800 Ohms could possibly indicate that the Sensor was Toast
And so without any further ado, I fitted the New Crank Sensor and then I Cranked her over, not knowing what to expect
Only this Time, She Really, Really, Really Tried to Start!
In fact She almost got there. at which point I decided to give her a little Squirt of Starting Fluid
Which had the opposite effect of what I was expecting, as after that She wouldn't Fire at all
Maybe that was as a Bridge too Far and She Flooded 'I just don't know'
So after I've had 'Me' Pizza and Chips and Numerous Cups of Tea, I try it again!
Although I am already Thinking that the Plugs will have to come out, in the event I can manage to find the Magnetic Pick up Stick you need to do this with
Before you pull the plugs, try my trick on clearing the flooding by keeping the throttle fully flat on the floor which cuts the fuel circuit whilst you're churning the starter. It'll then clear off unburnt fuel and start to stutter on the last bit left, then try lifting your foot to introduce fresh fuel and it should catch properly.
Also, it might still be struggling on the last bit of stale fuel and get better as you start to pull clean fuel through.
While I hate to disagree with you, I still think that I'm a very long way from having any Success because I don't think that the ECU is getting the Signal to keep Pumping Fuel
I'm thinking the 'Almost Start Situation' was more down to an initial build up of Petrol Pressure when I first Turned the Key to Position ONE, where she seemed so close to Starting, that I took out my Phone to make a Video
Although when I tried it a Second time, all the Engine did was Crank with no Signs of Life
If She had been getting Fuel then I feel sure the Spark Plugs would have Cleared
So my Plan for Tomorrow, is to disconnect the Fuel Feed from the Rail, exactly the same as I did before, only this time with the Crank Position Sensor still Connected and then Crank the Engine to see if Fuel comes pouring out in a continuous Stream
Then if it does or doesn't do that, then we will know as to whether or Not the Fuel Pump Relay is getting the Signal from the ECU
The somewhat Safer Option could be to ground one of those Wires on the Fuel Pump Relay, so that the Fuel Pump Runs Continually, as soon as the Key is Turned to Position ONE (obvs For Test Purposes Only) then we may be able to see if the Signal is missing (or not)
If we can get the Engine to run, then that may also have the effect of Waking up the Components
It sounds a good idea to me but I would like a Second Opinion from the likes of Greg and Grant and of course Yourself who is a Walking Talking Encyclopedia of all this sort of stuff, because as for me I do not see Auto Electrics anywhere in my future
So if you are all 'Green Lighting' this, which one of those Wires do I Ground from the Fuel Pump Relay, as there doesn't seem to be an Orange one
Unless of course anyone else has a better idea?
Which Wire in the Yellow Holder Should I Ground unless any one should have any better ideas?
If you can't verify from sound when you crank the engine if the pump is running, then turn on the ignition, wait a few seconds ( for the pump to cut out) then bridge terminals 30 to 87 on the relay holder. That should then provide current to the pump and it should run continously.
Trying To Start My XJS 4.0L Celebration Convertible With AJ16 Engine
Finding Out Why I'm Not Getting Fuel To The Rail When Cranking
As Without That She Has No Chance Of Starting
The 'Nightmare' Continues!
After a very Sleepless Night wondering if I would ever get this Car to Start, I really was beginning to Wish that I knew a bit more about Auto Electrics but trying to read a Manual or a Diagram, is one of those things that I've never been able to do and even if I could I just don't think I'd understand it
So trying to Fault Find Electrics on an XJS is going to take a lot more in the way of Luck than Judgement, for while I have managed to pick up a bit, this is one of those times when I wish that I knew a bit more
And so the way I saw it, the only way to start, was to use my DVM to test every fuse on the Car, including the ones that may not have had anything to do with the Fuel and after that then I'd check all the Relays just to see if I could find anything that didn't seem quite right
As I don't have any idea how you check a Relay and so I went through everything and that took me all day!
Where for reasons I cannot explain I remembered reading about an update from Jaguar about the Two Blue Relays which are hidden away above the Fuse Box behind the Passenger Knee Pad, on a UK Car
Where apparently there was a known Problem with the Blades of those Relays as they didn't always make Contact in their Holders Very Well, where Jaguar were advising to Swap the 2 Hella Relays DAC 7686 for JA-LHF 6703AA but unfortunately I hadn't got any of those
And so I did what I thought was the Next Best Thing and Bent the Relay Blades to try and get a Tighter Fit
So that's what I did and just when I was thinking that Miracles don't happen, I've now changed my mind because they do!
As when I went and Turned the Key to Crank the Engine Over, I was getting a Full Bore flow of Gas from the Pipe I'd hung over the side, that you can see in the Video above, which left me stunned with disbelief, that what I did actually worked
So after I'd had a bite to eat, I reconnected the Pipe to the Rail and then I cranked her over, hoping She would Start but that was the point where all of my Luck just ran out and realized I had more Work to do, so that's when I decided to follow Paul's (ptjs) advice and take the Spark Plugs out
Compared to having to do this on an XJS V12 even for me this really was a bit of a 'Walk in the Park' the only thing concerning me was the State of the Spark Plugs, that were all cover in thick Black Carbon like Goo
Plugs all covered in Thick Black Goo and they were all like that and not sure if that's anything that I should be worried about
Also How should I Clean them?
And then once having done so should I Test them all at once or one at a Time, as on the AJ16 each Plug has its own Coil and I'm guessing that it gets its Spark from the CPS Crank Position Sensor, which is really just a guess, as I do not know
The Cause of the No Fuel when Cranking problem was all down to these Blue Relays that are above the Fuse Box behind the Passenger Knee Panel
I guess my Next move is to Clean all the Plugs put them back and then try and Start her, although I have a feeling that I may have to Clean the Injectors
Check carefully when you buy Champion Spark Plugs. A few years ago, there was awareness of a lot of fake Champion items out there on the 'net. And they superficially looked good! Buyer beware!
I'll add my opinion to Greg's and Paul's recommendations (like that means anything here ) NEW plugs will solve a Lot of problems, and NGKs will solve the rest.
05-23-2023, 07:40 AM
) NEW plugs will solve a Lot of problems, and NGKs will solve the rest.