DPF mystery om651

[Cla2402]

Hi everyone! I have consistent issues with my dpf. When I bought my CLA with the om651 engine the dpf regened every 60-70 miles.

1.I had it at two merc specialists who looked at the car with xentry and found no issues

2. Dpf pressure sensor was replaced and the dpf was cleaned - this helped for around 15 thousand miles

3. During regens the dpf fill level reduces to only around 40%. The soot level then climbs back quickly.

4. Car runs absolutely fine with no issues, hissing noises, etc... please help as I am going mad!

 

[Dodipops]

Is it a forced regeneration you are doing then it goes to 40% fill level??

That can be normal as after a forced regen it leaves it at this level to initiate a normal regen (so that it happens on the road)

Do you have any diagnostic data on the dpf system you can post?

 

[91dm]

Do you know what the differential pressure readings are now and what the gram of soot at 40% is?

 

[91dm]

Forgot to ask, is the engine light on and do you have any current codes?

 

[Cla2402]

Diff pressure readings are around 8 milibars at idle - this is both just after a regen and when the filter is almost full eg fill rate 90%

 

[Cla2402]

No codes, car runs sweet. Only frequent regens are an issue. Things were ok for a while after the dpf was cleaned but now I am back to how it was

 

[91dm]

What type of journeys are you doing? I seen frequent regens a cause of short trips and soot accumulating quicker than normal.

 

[Cla2402]

Only motorway journeys, around 600 miles per week. Scanner shows no fault codes. I talked to an Indy and he does not know either so not very reassuring

 

[91dm]

It's possible the dpf may be partially clogged with ash content that the car regen can't clear itself but the actual clean did. That would explain the 40% fill after regen and frequency. What's the mileage on the car?

 

[Cla2402]

So the clean was done about 15k miles ago and currently it is showing as having 2.7g of ash. Where would all this extra ash come from in such a short space of time? Car has done 120k miles.

 

[91dm]

I think the ash is a calculated value as there's no sensor so i wouldn't trust this if all the values were reset. This would make sense why there's no codes at the moment.

You could try getting the dpf cleaned again with a strong solution to try and remove as much ash as possible but I think it usually signals the end of the dpf.

 

[Cla2402]

Yeah it seems like the dpf could be nearing its end of life though I have heard the om651 dpfs are pretty sturdy?

 

[91dm]

Yes I would say they're not the worst. How many miles have you covered in the car since you got it? Do you know any of the history?

 

[91dm]

Can you get the pressure readings at 2k and 3k revs, this would help to confirm whether the DPF is partially blocked or not? I think you're reading at idle could be lower but the higher rpm reading would confirm this.

 

[Cla2402]

At 2800rpm i have around 30 millibars, again either after a regen or even when the dpf is supposedly "nearly full"

 

[91dm]

Those values sound ok, with the engine off is it reading 0, good way to check the sensor is actually working.

What else could it be? Bad injectors, poor combustion creating excess soot? The soot value is calculated from pressure difference across the filter so not sure that makes sense.

 

[Cla2402]

Yes with the engine off it reads 0. When the dpf was off for cleaning i got some pics which i have attached. Injectors were tested with STAR and are supposedly ok.

 

[Cla2402]

 

[Cla2402]

When I go 80mph on the motorway, the dpf fill rate is minimal, however when i i slow down to 50 or 40mph i would say the dpf fills up by 1% every mile or less

 

[91dm]

People have different opinions on this but you don't necessarily have to remove the dpf if you're cleaning it again. Some solutions are stronger and will remove more ash than others, the trade off is you risk damaging the dpf. Had your indy any recommendations on what he was going to try next or what the issue/reason was?