My Citroen XM 3.0 PR-Vestige

[Dean]

I did John and I found it last night, very useful.
White label may be early ECU but my white label ECU (top picture) has a date in the alloy housing casting of July 94, now if that was cast in July 94 it would very nearly make that ECU a MK2 one surely, Lexia says it is a UFZ.
The green label one is a manual, you are correct which is why it always gives its transmission state as 'Drive', and probably doesn't have the fuel cut off on trailing throttle, Lexia tells me this is a SFZ.
It runs really lumpy on this ECU and super rich so I don't want to use it too much until I have done some digging.

All very interesting information and I will look more closely at the whole thing over the coming week, I think Paul is trying to find me another ECU, I want to test this theory they are interchangeable and what differences they have, Citroen says they are interchangeable I believe but I have differing failings with each ECU fitted which would make those faults ECU related.

It's all good fun anyway.

D

[Dean]

OK, had a real good bash at this today and found that changing the wiring to the TPS has upset things, i have swapped it back to how Paul had it and have got the Manual ECU to kind of work, idle is still way too low and it will stall in gear sometimes but it is a much smoother transition between trailing throttle and accelerating, the missing is still present though and i can rule out the ECU as the problem even though it is the ECU that does not output voltage to the front knock sensor, odd but the engine doesn't even seem to care if driven with both knock sensors unplugged.

Could someone else confirm if they get 5v on pin 2 (centre pin) on the front knock sensor, please

What i do need to sort out is why my engine is happy getting a reverse signal from the TPS, the only position recognised now is MID, lexia no longer says 'Idle' at Idle and Mid when the throttle is opened.
The sensor outputs 3.7v at idle now not .78v, WOT gives 2.3V and not the previous 3.9v
This is how the wiring diagrams say it should be though, it's just on the lexia screen it looks all wrong and the output voltages are the opposite to what the manual suggests they should be, getting closer to finding the problem though.

D

[Dean]

Checked injectors this evening, found one that has a single fine jet and actually fires a small quantity of fuel, it was one of the single nozzle types i had to fit due to having two failed injectors before.

I managed to get one of those failed injectors to work by repeatedly hitting it while supplying power so i have fitted it, the spray pattern now matches the other injectors but im not convinced this is the whole issue unless incorrect combustion in that one cylinder is messing with the O2 sensor readings and forcing the ECU to adjust fueling incorrectly on all cylinders to compensate, i will start it up tomorrow and find out as my battery has finally died, i have 12.1v at rest and 11.8v with the ignition on but it just wont turn over. all i can hear is the solenoid throwing the pinion out....................could be bad windings on the motor of course.

Injector with Renault Espace PRV part number
https://youtu.be/WakIjG2jG-I" onclick="window.open(this.href);return false;
Injector with Citroen XM PRV application part number
https://youtu.be/uwK_oUzXUfY" onclick="window.open(this.href);return false;

D

[misha]

Dean,that Renult Espace injector have wrong spray pattern because it is partially clogged.
As you know...injector must have a fine mist instead of jet like that,independantly from which car it came.
Other than flow rate,injectors also differ in resistance.Flow rate is usually determined with their color(yellow,orange,black,white...),but spray pattern,for a good working ones,is the same for all of them.

2nd injector for XM have a decent spray pattern.It should be better after professional ultrasonic cleaning and filter replaced.

[Dean]

Yes Misha you are of course right, the replacement one did start off with a rather poor pattern still, the vid of it was the first time it had fuel flowing through it and you can see if you look carefully that at times it sprays a two pronged jet rather than a mist, I suspect they are all not quite perfect but are now at the point that they should not cause significant running issues, they do really need to be properly cleaned though I think and if they hold out this may be a job for the winter.

D

[misha]

...if you look carefully that at times it sprays a two pronged jet rather than a mist...

Yes,i noticed that too.

[Dean]

Unfortunately, testing has not been possible so far this evening as the car will not start, it turned over great as usual last night and started right up but then cut out straight away.
I think it was because the fuel rail was full of air, i went to start it again and nothing.......... ah ha i thought! my battery problem, so i got my multi meter out and the battery is pushing out 12.3v, 11.9v with the ignition on, that should be enough to at least turn the engine though.

Tried jump starting and the same result, clunk.

The solenoid clunks and the body of the motor gets warm but there is no turning of the engine happening, i may go and jack the car up later and have a little investigate and see whats going on.

D

[Dean]

Problem solved.

The rear stator thrust washer broke up, now this is my fault as when i rebuilt the starter i saw the washer and thought it was just a shim, it was supposed to be a shouldered, thick, thrust washer not a shim!
This washer broke anyway, then jumped into the housing getting caught between the rotating stator and magnets that are bonded inside the casing, this promptly ripped one magnet off that stuck to the stator, crashing into the next magnet, ripping that off and so on, this jammed the motor solid leaving starter unable to disengage with the ring gear, which stalled the engine, of course, the starter would not actuate again as it was a chewed up mess.

With the spares i have from a 2.0 starter motor i salvaged a case with magnets in place and fitted the original stator with a nice thrust washer. I could not use the spare stator as the drive gear was too big. Whacked it all back together and its working great.

Just need to refit it, put the exhaust back on and my home made heat shielding to see if the injector issue was causing the running problem............. and then start looking for a cheap back-up starter motor just in case, im not sure i trust the stator in this one since it turned itself into a blender.

D

[Dean]

Can anyone comment on this, thoughts welcome

If i wire the TPS the way the wiring diagrams suggest the engine stutters when the throttle is opened and idle is unstable if i wire it up the way it works correctly as viewed in lexia live data (i know) everything works spot on.

This has come back around after sorting the injector and it does run surprisingly different now, lower and more stable idle speed for starters.

Could the wiring diagrams be wrong?

D

[Dieselman]

Possibly.

It only has 3 connections;
V input
Gnd
Signal to the ECU.

Just wire it so the ECU sees it working and it actually works. You could well ahve a mismatch of wiring loom and diagram.