DPF risk of particle filter becoming blocked

[pauljbl]

hi
this is on a c4 grand picasso 2012 has just had a new dpf fitted and about 2 or 3 weeks later i get the dpf warning back again this is why i had a new dpf filter.
i have put a new dpf pressure sensor on and still the same. it gets 7 milibar at idle and 120 milibar at 3000rpm stationary. Could it be the dpf additive needs refilling?
I dont have any other errors from diagbox. I am unsure what else to check.
can anone help.

[PontyAl]

Hi Paul.
I had a recurring issue with the DPF, had a similar problem with my 2.0 bhdi ds5 going into limp mode, risk of blockage warnings etc. I had the DPF cleaned and the pressures seemed fine, but faults reappeared. Apparently one of the reasons is there is a built in algorithm that forces limp mode and fault codes if several DPF regen failures are detected between services, usually caused by short trips. I was advised to reset the service monitoring to zero, press and hold the test button under the instruments while starting until the counter runs down from 9 to zero, a simple procedure and it solved my problem instantly. Not sure if that fix will apply but worth a shot, it'll just reset your service indicator.

[pauljbl]

Hi
I have already reset the service counter to zero. I think my pressures are too high on acceleration so think its not doing a regen for some reason

[Paul-R]

When the new DPF was fitted was the Diagbox used to reset the DPF life expectancy in the Engine ECU? Note, this is not the same as what PontyAl is suggesting.

You ask about the Eolys (additive) needing refilling. What level does the system think is still there?

[pauljbl]

Yes the dpf was reset to a new dfp in diagbox. The eolys says its still half full but wasn't sure if this is true or not from previous owners

[shtu]

120 milibar at 3000rpm stationary

Here's numbers for a Berlingo, viewtopic.php?t=82712

As for the additive - there's a pump flow test that you can perform with Diagbox. Disconnect the pipe, place a container to catch the fluid (I found a family-size yoghurt pot quite useful) and let the test run. Worth trying, mine had all the signs of working just fine, except no fuid at all came out.

I'd be tempted to disconnect and block the "pre" pipe from the pressure sensor, and see what is read by the diagnostics, could be an exhaust blockage downstream of the DPF.

[pauljbl]

I did try disconecing the pre pipe but not blocking it but the readings were almost the same

[pauljbl]

120 milibar at 3000rpm stationary

Here's numbers for a Berlingo, viewtopic.php?t=82712

As for the additive - there's a pump flow test that you can perform with Diagbox. Disconnect the pipe, place a container to catch the fluid (I found a family-size yoghurt pot quite useful) and let the test run. Worth trying, mine had all the signs of working just fine, except no fuid at all came out.

I'd be tempted to disconnect and block the "pre" pipe from the pressure sensor, and see what is read by the diagnostics, could be an exhaust blockage downstream of the DPF.

If the dpf fluid pump is pumping slow would this stop regens. I tested the pump and it worked but only pumped out 4ml instead of the 20ml it was meant to according to diagbox pump flow test.

[GiveMeABreak]

No, this wouldn't affect regeneration from the pump / additive metering perspective, as the additive is only added to the fuel tank in multiples of no more than 1.2 mm, depending on how much additive is required, determined by the fuel added as calculated by the engine ECU.

Regeneration only becomes a problem if the exhaust gasses are not getting hot enough for either an assisted regeneration (450 °C) or passive regeneration (550 °C).

In other words the additive pump itself not working does not stop regeneration taking place, but obviously if the additive pump is not working, it's not dosing the fuel, which mans regeneration is therefore dependent upon passive regeneration, but this requires a hotter exhaust gas temp., as explained. If the filter can't regenerate then obviously it will become blocked - and this is where the DPF pressure sensors will alert the engine ECU.

We would really need to see some parameters from Diagbox for your vehicle similarly to those shown in the link for a Berlingo a few posts above.

For example, for a replaced DPF, we would expect to see the total weight of additive deposited in the particle emission filter close to zero.
We'd also expect to see the Difference in pressure between the differential pressure sensors as close to zero with the engine off.

[pauljbl]

No, this wouldn't affect regeneration from the pump / additive metering perspective, as the additive is only added to the fuel tank in multiples of no more than 1.2 mm, depending on how much additive is required, determined by the fuel added as calculated by the engine ECU.

Regeneration only becomes a problem if the exhaust gasses are not getting hot enough for either an assisted regeneration (450 °C) or passive regeneration (550 °C).

In other words the additive pump itself not working does not stop regeneration taking place, but obviously if the additive pump is not working, it's not dosing the fuel, which mans regeneration is therefore dependent upon passive regeneration, but this requires a hotter exhaust gas temp., as explained. If the filter can't regenerate then obviously it will become blocked - and this is where the DPF pressure sensors will alert the engine ECU.

We would really need to see some parameters from Diagbox for your vehicle similarly to those shown in the link for a Berlingo a few posts above.

For example, for a replaced DPF, we would expect to see the total weight of additive deposited in the particle emission filter close to zero.
We'd also expect to see the Difference in pressure between the differential pressure sensors as close to zero with the engine off.

I don't have screenshots of the data but I can remember

With engine off it was 0
Idle was 10 mbar
2000 rpm 50 mbar
3000 rpm 100 mbar
Full revs 150mbar

I did try a new pressure sensor but gave the same values

A couple days after the pressure readings went even higher and the car limited the revs to 3000. I did a forced regen that brought it back to the values I listed here but still warnings

I noticed if I cleared the fault as soon as it went over 100mbar the filter service light would come back on. It was a aftermarket dpf so wondering if this is giving the troubles

The old dpf I have had off the car a few times to soak in dpf cleaner which fixed it for a few months then the warnings came back

[GiveMeABreak]

Well it's possible as after-market kit is risky and they are not all made the same, especially cats and DPFs and won't be anywhere as near as good as an OEM one - which should last a good 120k -140k miles depending on vehicle, year and conditions of course.

But assuming the sensor is good, the sensors are detecting a blockage so I can only suspect the AM DPF may be either the incorrect type or just poorly made. If you have the part number for the filter you had fitted, I can at least check to see if it was the correct one.

[pauljbl]

Well it's possible as after-market kit is risky and they are not all made the same, especially cats and DPFs and won't be anywhere as near as good as an OEM one - which should last a good 120k -140k miles depending on vehicle, year and conditions of course.

But assuming the sensor is good, the sensors are detecting a blockage so I can only suspect the AM DPF may be either the incorrect type or just poorly made. If you have the part number for the filter you had fitted, I can at least check to see if it was the correct one.

I am not sure on the part number but it was bought using the registration of the car and looks identical.

Is there anything else you could think of checking? There are no other codes in the car.
Someone said glowplugs could cause it but there are no codes for them not sure if they can go faulty without a code showing.

Does the car tell you if it is doing a regen while you are driving as never seen one?

[GiveMeABreak]

No, glow plugs (as far as regeneration goes) are only used for post injection when commanded by the engine ECU to assist with getting the temperature up. The engine ECU has other strategies like putting a load on the engine by activating electric consumers like the heated mirrors and rear windscreen if it needs to.

But that would not be causing the blockages and it's not good to force regeneration at standstill either because of the strain that is put on the components without the cooling of a moving vehicle.

[pauljbl]

No, glow plugs (as far as regeneration goes) are only used for post injection when commanded by the engine ECU to assist with getting the temperature up. The engine ECU has other strategies like putting a load on the engine by activating electric consumers like the heated mirrors and rear windscreen if it needs to.

But that would not be causing the blockages and it's not good to force regeneration at standstill either because of the strain that is put on the components without the cooling of a moving vehicle.

What should the exhaust temp be for a average drive out. I took it out for a 15 min drive and was around 250 deg most of the time

[GiveMeABreak]

Regeneration only becomes a problem if the exhaust gasses are not getting hot enough for either an assisted regeneration (450 °C) or passive regeneration (550 °C).

That won't be hot enough for a regeneration. In order to get an assisted regeneration, you'll need to get it to 450 °C, so will need to drive it in 4th gear at say 40 MPH for about 20-30 minutes, ideally with no stop / start traffic as a minimum to get the exhaust gasses to reach this temperature as a min.