Adblue tank repair details

[Trickiedickie]

@Stuart W. Thank you for your explanation. I haven't yet tried any experimentation but I am in the process of collecting info for when that bad day arrives.
I have read through much of the marathon thread posted on the Elektroda forums and from the post by mako122 I borrowed this image detailing much of what you have deduced indicating 4.9 to 6.1 bar would have a voltage range 1.5v to 2.8v in which case your choice of a 10 bar sensor was likely to be very wise. Out of interest, what sensor voltage range did you find with your own modification?

Source: Repair of the AdBlue tank PEUGEOT BOXER III, CITROEN JUMPER https://www.elektroda.com/rtvforum/topic3827598-60.html

[Stuart W]

I cannot recall from memory whatt the sensor output was at the turn off point but did read the output pressure at 6 bar, so I was very happy with that. Some where in my scribbled notes, will be the output voltage !The srndors generally give a linear output voltage from Zero at no pressure and increasing up to 5 volts at the sensors rated pressure.Hence with a 10 bar sensor,reaching the required 6 bar it should be 0.6 of 5volts, i.e. about 3 volts.
The pressure sensors used by PSA did seem to be very unreliable and the main culprit for countless adblue tank failures.

[Stuart W]

Just one more point.Do not rely on any diagnostic read out to read the adblue pressure, these only monitor the voltage output from the sensor and if you have fitted a 0- 6 bar sensor or a 0-10 bar sensor the actual pressure would be completly different. The read outs from the diagnostic may appear ok as it only interprets the sensor voltage and the controller cuts the pump off at about 60 percent of the maximum sensor output.
The only way to check what the sensor is regulating the pressure to is to fit a pressure gauge straight onto the output of the pump when the engine is up to temperature and the adblue controller is running the pump.
In my case the 10 bar sensor settles the system at about 6 bar adblue pressure.Also, standard 10 bar sensors seem to be readily available.With an 8.5 or 9 bar sensor it would probably give 5 to 5.5 bar adblue pressure which would give the pump a slightly easier life.

[Trickiedickie]

In my case the 10 bar sensor settles the system at about 6 bar adblue pressure.Also, standard 10 bar sensors seem to be readily available.With an 8.5 or 9 bar sensor it would probably give 5 to 5.5 bar adblue pressure which would give the pump a slightly easier life.

I think you are right. From what I understand the pump pressure starts to be registered by the control board/ecu at about 5 bar and reaches the optimum/maximum working pressure at about 6.1 bar.

Your work has been an eye opener. The repair you carried out is excellent. I do have an alternative repair option in mind to fix this fault which I will post in another thread.

[Stuart W]

If someone could make a plastic moulding (3d printer?) to make a suitable adaptor for the original sensor but with a thread to accept the standardly available pressure sensor this could be screwed straight into the existing pump housing with no pipe or connector modifications at all.

[Trickiedickie]

That would be a cool project for somebody.
My plan 'A' would be to source an identical sensor to the original from China. Yes they are available.
Or my plan 'B' would be to source a near identical sensor, also from China.

[C4Picasso]

Hi Guys, new member here after finding this thread in the interweb. I ended up replacing the adblue tank on my c4 grand picasso few weeks ago after the dreaded permanent P20E8 error code. I have kept my old tank and wish to revive it and hopefully this is one solution to try out. Thanks.

[Stuart W]

Hi C4 and welcome to this forum.I have always found the guys here very helpful.
Was your adblue tank failure preceded by the sounds of the pump working hard and for longer periods than longer?If so , then there is a good chance that it was the failed pressure sensor not working and demanding more pressure from the pump.If so, you should be able to do the external sensor mod and repair the tank.Let us know what you find.

[C4Picasso]

Thanks, Stuart. I will definitely give this a try. I just don't want the tank and it's components thrown away yet. I had those pump whirring moments as you described during my problem diagnosis phase and a few alarm code cancellations.

[Ceenine]

Any chance of a basic diagram of fitting items together. I am a bit challenged in this regard but A1 competent on garden hose fittings.

I have purchased all the required items from either China or my local gas fitter.
Don

PS My friend who is an industrial process engineer says that pressure sensors have a very finite life. Probably explains why some owners are on their third tank. They fail causing a say $3000 AUD tank to be sent to the rubbish dump because of a $20 AUD part which can’t be replaced separately.

[C4Picasso]

Just sharing my black box (or white box) solution in the future. Looking at attaching a 3pin connector at the end to allow flexible placement. Thanks, Stuart W. for sharing your initial solution. For now, I'll relax for a bit.

[Stuart W]

Good thinking c4.My initial fix was not quite as neat, especially not knowing if it would work! There is very little space around the adblue tank to fit the external sensor so extended pipes make good sense.My original repair still works fine though.

[Clockworkcitron]

I am impressed by the detailed documentation and grateful that you share the knowledge to others, thank you!

Guess what, our lovely 2016 C4 Grand Picasso alarms check engine light and urea. Fault code 208E no countdown yet. Fault was intermittent but seems to be permanent now.

So, I took down the adblue tank. I have opened the lid to access pump and electronics. I have tested the pump at 12 volts and measured the output pressure. In less than a second it reaches above 6 bars and beyond. But when supplying 11.9 volts and 4 amps maximum pressure was 3.5 bars.

I Have not diagnosed the pressure sensor yet. However I have noticed that when the tank was fitted it primed the pressure for several seconds when in "run" mode. Maybe the circuit board cannot deliver enough amps? Time for an auxiliary power supply to the pump?

I guess I need to diagnose the pressure sensor to rule that one out first.

By the way, do anyone of you know about a car diagnose tool that access the adblue components (show pressure, temperature, and etc.) and that also can actuate the adblue pump and cost maximum 400 - 500€? Please let me know.

[Stuart W]

Hi Clockworkcitron, The pump has to be controlled by the built in power supply because thecpower controller operates in a bridge mode which controls the power to yhevpump according to requirements and reverses the supply voltage when the ignition is turned off in order to relieve the stored pressure and return the adblue back to the reservoir.
I tested my pressure sensor in situ by running the car a few miles to bring the engine temperature up, and get the adblue system operating, which normally is within a couple of miles.Then after turning off the engine the pump will reverse and relieve the pressure.Take the adblue connector off the tank and fit a pressure gauge, about 0 to 20 bar onto the outlet from the tank.Start the car , leave it running and watch the gauge .After a while you will hear the adblue pump run. Note the pressure on the gauge. If it runs up above 6 bar, then it indicates the most common fault,a faulty pressure sensor giving no output signal so the pump just keeps on running trying to increase the pressure.
The mods that I and others have detailed on this thread should cure that.
Incidentally, it is easier to connect the pressure guage at the front of the car by removing the adblue injector connector and plugging the guage in there.It is easier to access being just under the front of the engine.

[Paul-R]

I don't know if it's been posted before but I fell over this post on YouTube over the weekend. It's well worth the thirty odd minutes you'll have to watch for.