Exhaust back pressure and DPF diferential pressure

[Cal39]

Hi I got the autel 802 code reader and it gives exhaust back pressure and DPF differential pressure. Does anyone know what "normal" reading should be?
And should they be measured at idle or other rpm?

Im getting.

13hPa at idle on DPF differential pressure and

1240 hPa for exhaust back pressure at idle


2011 3500 MB sprinter. Thanks

 

[Gessippi]

I have that same scanner, it has allot of good info like that but if you don't know what parameters are good and or poor it's kind of useless.

 

[smiller]

I don't see anything in the factory service manual that describes what the values should be. I suppose we could compare notes and perhaps get a baseline from newer vehicles but probably the best thing to do (if the vehicle is otherwise running normally) would to be to just look for any significant negative changes or trends over time.

 

[nbarnard]

I have same scanner and love it. I just watched an active regen on my 2007 2500. Noticed exhaust temp upstream of dpf was 650-750, then dropped to 350 after. Last regen was about 900 kms ago.

Soot content dpf varies from 3-6 g/l. Seemed to increase as I hauled trailer uphills under load as exhaust temps increased. I thought the higher temps would drop the soot level. They do drop as temps fall. Also regen didn't seem to drop soot reading.

Still trying to understand how all this works and is measured. Also considering a dpf delete and retune.

Nathan

 

[nbarnard]

Fwiw I am getting 2500hpa back press and 90hpa dpf diff cruising on level ground. 180hpa at WOT.

 

[vertigo]

Hi I got the autel 802 code reader and it gives exhaust back pressure and DPF differential pressure. Does anyone know what "normal" reading should be?
And should they be measured at idle or other rpm?

Im getting.

13hPa at idle on DPF differential pressure and

1240 hPa for exhaust back pressure at idle


2011 3500 MB sprinter. Thanks

Adding another set of data-points from a 2007 3500 with recent recurring, key-cycle resettable LHM issues and a 2626-1 DTC as shown on my new MD802 scanner:

Exhaust Back Pressure at idle - 1517 hPa
Pressure Differential in DPF - 138 hPa

As I increase rpm to 2000 rpm (parked), back pressure increases to approximately 2000 hpa, and differential climbs to above 200.

I'm not ready to swap out sensors just yet, though. Visual inspection of the Y-cable reveals an alarming degree of swelling and brittleness of the cable's insulation, particularly around the fusible link, which prompted me to take a closer look at system voltage - 13.4v - not the 14.1v that I've seen recommended in other threads.

Will be replacing the Y-cable tomorrow, then re-testing. Odds are at least even that I've been replacing lots of expensive parts needlessly!

More to follow...

 

[vertigo]

Will be replacing the Y-cable tomorrow, then re-testing.

More to follow...

...and still waiting on that Y-cable delivery.

Update: My new Y-cable finally arrived this afternoon. 15 minutes later it was installed and ready for testing. Initial test showed operating voltage steady at 14.2 volts, and quick cold-start. Very nice improvements generally, but no significant improvement to my DPF trouble-code situation causing recurring Limp Home Mode (DTC 2626-1).

My MD802 now shows approximately 1250 hPa for exhaust back pressure, and about 80 hPa differential pressure at idle (down from 1517 / 138).

Next we (my assistant and I) disconnected the pre- and post-DPF pressure lines from the DPF and tested the differential pressure sensor by having my assistant blow into each pressure line alternately while I observed the scanner live data for changes in differential pressure readings. Apparently my assistant can produce 42 hPa (0.61 psi) pressure blowing on a nasty metal tube while laying under a Sprinter. Apart from that trivia, I deduce that the differential pressure sensor is working normally.

Since I still could not clear the 2626-1 DTC, and LHM mode continued to be triggered on acceleration (approx. 2100 hPa exhaust back pressure), we decided to pull the DPF for a visual inspection. 10 minutes later, assistant had the DPF on the bench, and it was black as night with soot - confirming the suggestion of the trouble code.

Since it's a long way to drive to the nearest MB dealer for a forced regeneration of the DPF (which might not be possible considering the 41 g soot loading and 2626-1 code), I've decided to do my own DPF hot oven cleaning. Tomorrow morning I'll assemble a firebrick kiln and bake that sucker at 1100f for a few hours, and then install and re-test its differential pressure again.

One way or another, that DPF is gonna give up some flow!

 

[chrispsprint]

How did the cleaning go

 

[Dr. Soot]

Replace your DPF sensor, that failing sensor will cause failed regens and will also keep kicking it into limp mode. Baking that style of filter isn't always a sure thing because of the way it's build.
The larger 2 piece types get the best results from baking.

 

[Frank Mc]

Guys, my MD802 is telling me that the DPF is too clogged to regen so I'm assuming that it can only be cleaned by taking it out and manualy cleaning it , chemical or roding it out ??
Please give me some ideas . Thanks, Frank

 

[mikeme]

http://www.fsxinc.com/index.html

These guys can clean it for you (or point to someone closer)

but you want to know why it got so clogged.

is there a sensor malfunction?

do you idle it for hours?

 

[Frank Mc]

Thanks, Mike , but I'm trying to figure a way of rodding and chemicaly cleaning it . Another ? Why do so many guys on this forum change the Y-cable ? I would think if it was not burnt and had good contacts it should be just fine but instead so many guys just change it out !

 

[Frank Mc]

Also Mike, I do not idle it very long at all . Here are the DTC's 2079 , DPF differential press. , 2501 boost pressure regulator signals fault 2626 DPF soot content too high for regen.
2116 misfire detect cyl 4 # of misfires is too high 2011 charge air system , airmass too small. I'm wondering is the DPF being clogged could maybe cause the other air mass DTC's to be
wonky. ? Frank

 

[Rob S]

I'd say all those symptoms might be more likely a faulty sensor is causing the engine to run all wrong, thus pumping out to much soot... Lack of boost also causes excessive soot.

These sensors can be a bit tough to track down. Lindenengineering has posted some procedures to test at atmospheric pressure to make sure all read the same.

Injector cleaner just might clean up the Cylinder 4 misfire, but you'd have to be able to run it for a while, which it won't do very well right now.

You could try cleaning or replacing the MAF sensor.

 

[Frank Mc]

Also again ,, I know that I am running the wrong oil [ 229.5 instead of the 229.51] but I'm planning on a GDE delete of EGR and DPF so I'm thinking it will be OK to run this oil after the delete . Of course I would change the oil again . The correct oil is hard to find and spendy . Basicly I'd have a V6 T1n . I can't live with the van as it is 08 . Too spendy to have it serviced at MB or Dodge , money I don't have . I'm trying to have a vehicle that I can trust at long distances from my home . thanks, Frank

 

[smiller]

Also again ,, I know that I am running the wrong oil [ 229.5 instead of the 229.51] but I'm planning on a GDE delete of EGR and DPF so I'm thinking it will be OK to run this oil after the delete . Of course I would change the oil again . The correct oil is hard to find and spendy . Basicly I'd have a V6 T1n . I can't live with the van as it is 08 . Too spendy to have it serviced at MB or Dodge , money I don't have . I'm trying to have a vehicle that I can trust at long distances from my home . thanks, Frank

The correct 229.51 oil is frequently (every couple of months) on sale at NAPA for about the same price as any other synthetic diesel oil. What many of us do is just stock up while it is on sale, and that way there is no real additional cost for the recommended oil.

 

[benventerrr]

Frank Mc, have you gone ahead with the dpf delete? I'm in a similar position, my van keeps throwing the p242f code and sending the vehicle into LHM. I just replaced the DPF with a refurbished one and the code comes back even though the new one is in good shape. I'd like to get the GDE tune and am also considering deleting the DPF because I want a reliable van that doesn't leave me stranded hours from home on a regular basis.

Do you know how involved it is to delete the DPF? I hear this is illegal and I wonder what other repercussions it has for the van... does it involve reprogramming the computer to ignore the dpf pressure sensors etc?

 

[lindenengineering]

Frank Mc, have you gone ahead with the dpf delete? I'm in a similar position, my van keeps throwing the p242f code and sending the vehicle into LHM. I just replaced the DPF with a refurbished one and the code comes back even though the new one is in good shape. I'd like to get the GDE tune and am also considering deleting the DPF because I want a reliable van that doesn't leave me stranded hours from home on a regular basis.

Do you know how involved it is to delete the DPF? I hear this is illegal and I wonder what other repercussions it has for the van... does it involve reprogramming the computer to ignore the dpf pressure sensors etc?

First a question here?
Why don't you take it to a competent repair shop (like a dealer) and get it fixed so that it stops throwing codes and LHM's if you can't DIY fix it?
Curious?
Dennis

 

[benventerrr]

Hi Dennis,

I will take it to the dealer to have them clear the p242f code. Is this really something only a Sprinter dealer can do?

I had my dpf repairs done at 2 non-sprinter specialists because they were the shops that happened to be nearby when I broke down. I was traveling and didn't have access to a truly competent mechanic. I live in Lander, WY and will try to take it to my local dodge dealer. I believe they employee a sprinter mechanic but I'm often traveling ( and breaking down ) in places with unknown mechanics.

I'm considering the GDE tune in hopes that I can avoid breaking down so often. I'd love to take the van to see you in Golden, it probably would have saved me a lot of time, money and stress. I'll definitely schedule my next service with you. It has been hard to find a good mechanic that I trust.