Dpf back pressure

[Pvapour]

Fitted a new dpf 2 moths ago along with a load of new overdue stuff that was stopping regens.

Now regens fine, no faults, engine temps correct.

But app was showing 14psi back pressure for dpf, no fault lights or codes and car ran fine but there was a bit of black smoke so took dpf off and cleaned it through, was quite blocked as water wouldn't pass through easily, (there was a short period of running new dpf with no regens) free flowing after oven clean and jet wash.

All this done but psi is showing the same, rises and falls with rpm so think sensor is ok, small amount of black smoke has gone (dpf working better)

Regens are reducing soot mass from 30 - 0g ok but ash mass remains at 39g which I thought would hav dropped with manual clean, or do u have to instruct a new dpf fitted after manually cleaning ? There aren't any sensors on the Dpf..

Any ideas?

[Pvapour]

Sorry, e60 530d 2004

[Matt Seabrook]

You would normally measure dpf pressure in mb. A good one at idle would be 10mb or less bring revs up to about 2500rpm and less than 100mb flat out under load and 300mb max. 300mb is about 4.5 psi. Ash content is a calculation and needs resetting on diagnostic tools after a dpf is replaced. I would be confirming dpf pressure with a gauge and than supplying a know pressure to the dpf sensor checking live date to confirm performance. If your pressure readings are correct you have a problem.

[Pvapour]

Thanks, the dpf is very easy to remove so did that, and its as clear as you like, coupled up an air line set 1 psi and it flowed freely, the only other thing is the cat (theyre seperate on pre lci). Could that be blocked? Its the only other thing in the system that could cause back pressure really apart from manifold, where along the system does the pressure sensor sit, do you know?

Did a long run at weekend, mpg was fine, pulls like a train but a puff of black (diesel) smoke out back under initial acceleration, varies, sometimes heavy sometimes very little.

Will test sensor next, its values do rise and fall with revs, is it possible to be faulty and still measure increases / decreases??

Edited by Pvapour on Wednesday 17th May 05:55