Adblue tank repair details

[Stuart W]

Some of you may have seen my posts on here when my 2015 Grand picasso suffered the all too common adblue pump failure with persistently screaming pump and Service light on, engine fault light and urea light on.
Diagbox says leak/ low urea pressure.
It is worth noting that diagbox says pressure is 4 bar even when its actually zero.It does not read below 4 bar.
However, when I removed the tank and ran the pump directly from 12 volts with a pressure guage attached to its output, the pressure shot up immediately way past the required 6Bar, reaching 8 or 9 bar in seconds.So the pump was not faulty.
The culprit was the pressure sensor that is built into the pump body.I metered the output from this sensor and it did not register the pressure changes at all.This explains why The pump was screaming, trying to reach a pressure that was not being seen by the sensor although in fact it was already too high.
The faulty sensor also mislead diagbox and me for a while, by saying the pressure was too low.The system will not inject the adblue if it thinks the pressure is too low.
This noisy overworking adblue pump seems to be a commonly reported problem so I suspect that the majority of adblue tank failures are due to this sensor.
THE FIX.
Since the original sensor is a purpose built part moulded in plastic and attached to the pump motor it cannot be replaced without PSA manufacturing a spare part.
The answer is to fit an external sensor in the urea output pipe that runs to the injector.
I bought some 6mm fuel line connectors, male and female ant with some 8mm hose and 8mm brass tee piece inserted this short extension pipe from the output of the blue tank.The Tee piece connects to an 8mm to femake G3/8 thread adaptor to accept a standard 3 wire pressure sensor (10 Bar)
The existing Citroen pressure sensor has a small 3 pin plug with red,black and yellow wires.Unplug this from the sensor and connect the new sensor to the same wires.In my case the new sensor had a green wire instead of yellow, but connect this green wire to the yellow of the Citroen lead. The Red wire is + volts supply and the black wire us - volts supply.The yellow or green is the sensor output which should move from 0 volts up to 5 volts as the pressure increases.
Since the sensor comes with about 30 cm of wire attached you will need to drill a small hole in the plastic lid which covers the pump and its electronics.
Feed the sensor wire through this and connect the red, black, green wires to the old sensor lead.Seal the cable hole to prevent dirt and moisture getting to the electrics.
While the tank is out, it is worth offering up the Tee piece extension hose to find a suitable location for the sensor to fit as space is limited between the adblue tank and the spare wheel.Adjust the hose length to allow the sensor to fit into one of the recesses in the tank moulding.
For belt and braces, I put two jubilee clips, close together, on each pipe joint. So 12 hose clips in all.
It may be necessary to bleed the adblue system with diagbox before clearing all error codes.In the course of doing this mod I have only had to bleed the system once.Previous times it was ok.
To see what is happening with your faulty tank it is worth checking the pressure by using a piece of this same 8mm pipe and clip on 6mm fuel line connector running to a 0 to 10 bar pressure gauge, also available from ebay or Amazon.Once the engine is warm the adblue pump should operate periodically to bring the stored pressure up to 6 Bar.
If your adblue pump is screaming and the fault codes are saying low pressure then it is worth doing this low cost fix.
All parts were bought from Amazon for a few pounds.See my attached photos.

[CitroJim]

That's fantastic Stuart and huge thanks for posting this, most valuable in the extreme

[shtu]

That is some impressive work.

Might be worth pointing to a couple of suitable pressure sensors?

[Harrythephot]

Fantastic job.
I wonder how many tens or hundreds of thousands have been wasted on new tank fitment, when a simple repair may have worked.
Well done.

[Stuart W]

The pressure sensor that I used was a 0 to10 Bar 3 wire sensor which is available on Amazon or ebay.I will post the part numbers of the unit I used.Incidentally , when I tested the actual fluid pressure with the new sensor , it was 6 Bar which is spot on.

[wheeler]

Excellent job

[Stuart W]

PARTS LIST
Parts list for adblue tank repair.All are Amazon part reference numbers (ASIN)
I have not included the jubilee hose clips which are readily available elsewhere.

Pressure sensor 10 bar 3 wire type B08DKFKLWK.

G3/8 Thread adaptor for sensor B09BQF8HC8

Autohaux fuel line connector pack 6.3mm B0BSDB8YC4

Brass 8mm Tee piece B07MX7DZ4X

8mm fuel hose B0C5CPT9QQ
These parts are all from Amazon.and total about £ 30.No doubt some may be available for even less online but I was keen to get the car fixed asap.

[Philip Radford]

Do you mean .7 bar (10.1526 PSI)


You say 7 bar ( 101.526 PSI) and that seems a but high for the plastic pipe and fitting in the system.

the live data readout on my c4 is expecting to see calls for 0.500007799psi ( 5bar )

I was just wondering if it was just a typo in the thread.
Please reply

[RichardW]

No, it's def 5-6 bar, 75-90 psi.

[Philip Radford]

Ok that's fantastic, thanks for the reply. just ordered using the part numbers in your post.
My test procedure as follows:
I removed all connections, from motor, solenoid, pressure sensor before using any external test equipment (test gear).
So no connections back to the car or the AdBlue tank. so the motor, solenoid, pressure sensor are completely isolated from any systems.

I supply 12 volts to the pump and fed AdBlue fluid from a jar into the input of the pump and another pipe from the pumps output back to the jar.
Pump ran but no pumping, although the pump was clearly sucking.

I then fed the priming solenoid with 5v that allowed AdBlue fluid to circulate around the jar.

Next i supplied a separate 5v to the pressure sensor black- red+ yellow being where one should see a varying output voltage depending on pressure of the fluid in the system,
basally i clamped the fluid pipe from the pump to the jar (return pipe) making the pump work harder, which obviously increases the pressure, got a flatline Reading from the pressure sensor.(no change in output voltage from the centre pin of the pressure sensor.)

So i think its safe to say the built in pressure sensor is bad.

I will post the results if anyone's interested.

I do intend to back work this system, and the Eolys fluid system, although I've done quite a lot of work on mine to get it up and running correctly.

[Philip Radford]

hi all, i can confirm Stuart W Adblue tank repair details do work.

i used all the parts suggested by Stuart W.

This is the description of the pressure sensor i used from Amazon

(Fafeicy IP65 Analog Signal High Accuracy Water Pressure Sensor (0~10 BAR), Pressure Sensor)

witch is the same as the one in the photo in Stuart W post.

i installed it slightly differently to Stuart W.

I don't recommend fitting it this way like in my photos, reason being, in the event of a leak from either pressure sensor or fitting even the rubber pipe, there's a potential to damage the internal workings of the AdBlue tank.
As I won't be actually running this on the vehicle (just a test bed for me) this will not be a problem.

[Stuart W]

Hi Philip, Yes, I also worried about a potential hose joint leak inside the electronics enclosure, so that is why I kept all the modified pipework outside of the enclosure with only the sensor wires going back into the enclosed pcb.
Not quite so elegant, but safe if any leakage should occur.I have done several thousand miles now since I fitted the external sensor and still no problems whatsoever.

[Johnoxo]

Good work guys.

[Trickiedickie]

Thanks Stuart W for the very useful guide.
Iread the other thread viewtopic.php?t=81085&start=15 and then found my way here.
I do have a question..........as the original pressure sensor has failed you chose to use a 10 bar/150psi sensor as a replacement. Why did you choose it over a 6.9 bar/100psi sensor.

[Stuart W]

Hi, Initially I chose the 10 bar sensor as a guess because the sensor has an output which varies linearly as the pressure increases.This would mean that if a sensor which would only operate when the required 6 bsr was reached it would probably have been a simple on- off sensor which would not have given any actual pressure readings back to the control board(and the diagnostics).You may have heard the motor kick in.Sometimes it is just a gentle hum if the pressure is just a little low, other times it runs harder if there is an increased demand from the ecu.It seemed likely that the sensor would therefore have its normal operating point near the centre of its range and my tests showed that the pump kicked in when about half the sensor voltage range was reached.
In my case I put a pressure guage directly on the pump output and it cut out at 6 bar when a 10 bar sensor was used. I would guess that a 6 bar sensor would limit the pressure to abou 4 bar as the output voltage from the sensor would be reached at a proportionally lower pressure.