Volvo V70 in for DPF (Diesel Particulate Filter) problem

In the workshop today:

MAKE

Volvo

MODEL

V70

MILEAGE

85000

YEAR

2002

We recently had this Volvo V70 in for DPF Diesel Particulate Filter problems referred to us by another garage.

We did a diagnostic check using Autologic and it came up with this error:

  • 2A30 PARTICULATE FILTER: BLOCKED (as seen in the photo)

Which means that the Diesel Partculate Filter on the exhaust is blocked.

The Diesel Partculate flter is made to collect soot partcles and when it reaches a certain amount of partcles collected the engine control unit then initates a regeneraton cycle, which it then heats the D.P.F. up to around 600 degreas. This is achieved by the Engine Control Unit making the injectors fre a set amount of fuel when each cylinder is on its exhaust stroke causing the D.P.F to burn the ash and partculates held inside of it which then in turn makes the ash content lower. The Engine Control Unit measures the ash content in the D.P.F by using a (back pressure sensor). Which is connected by a pipe to the exhaust just before the D.P.F.

A clean low ash content dpf will let Exhaust gas freely flow through it thus making low back pressure which the back pressure sensor picks up. A D.P.F needing to regenerate and starting to become restricted will restrict exhaust fumes fowing through it, causing high back pressure which the Engine control unit picks up via the pressure sensor and then initiates a regeneration to burn off the ash.

On a lot of models of car, when the Engine Control Unit initiates a regeneration. It will switch on the engine glow plugs to try and raise the engine temperature in the exhaust to help burn of the Particulates.

Some tmes though the D.P.F gets to blocked and can no longer Regenerate.

This can be caused by the customer doing to many short journeys not giving the car enough tme to warm up to get the D.P.F flter hot enough to burn of the ash content.

Or it can be caused by various faults on the engine. Most commonly a turbo leak, faulty pressure sensor, Glow plug fault, D.P.F filter aged and corroded and reached the end of its life, Engine burning oil making excess soot, sticking exhaust gas recirculation valve…and many other faults!

Ok back to the car in queston

We then looked at the live data on autologic and we could see that the particulate filter ash content was at 90 grams of ash. This should only be around 30 grams normally, so the filter was very blocked. We then visually inspected the D.P.F pressure pipes to make sure they were not split as they can melt from the over pressure and heat when a D.P.F. is this blocked. They were ok.

We did however notice the engine swirl fap linkage was very loose and had major play in the linkage and shaft and was leaking turbo pressure from it which could cause the D.P.F to block. Also We tested the glow plugs with a glow plug tester which saves removing them from the engine to test them. The vehicle was a 5 cylinder with a glow plug for each cylinder, When we tested them only 2 were working. These would also not be helping the problem, as I said before they are activated when the vehicle wants to regenerate.

So we rang the customer to advise him of this and he requested that we replace these worn parts. We fed the new Glow plugs and the swirl fap linkage and swirlfaps.

We then ran the car up, and initiated a Forced regeneration with Autologic. (this is where the diagnostc computer connects to the Engine Control Unit and forces the car To go into a regeneration cycle. How ever we could not get the D.P.F to come down clean enough as it was so blocked.

In fact this D.P.F. was so blocked it would need to be removed from the vehicle and chemical left in it overnight to dissolve all the solid carbon inside the filter.

We do have a Liqui molly D.P.F cleaning gun which can clean D.P.F’s on the vehicle but this one was so extremely blocked – the only option was to remove it and leave the chemical in it over night.

So we then contacted the customer and told him the unfortunate news. We then removed the D.P.F. filter from the exhaust (see photo) and poured the chemical into the filter and let it soak over night.

Then we refitted the D.P.F. filter to the exhaust and again carried out a forced regeneration.

Result:

This time it cleaned the filter grams of ash right down to 3 grams when it had finished

We then cleared all the faults with autologic and reset the D.P.F. learned values and carried out an extended road test. Then we returned to the garage and rechecked for any returned faults. None were found and the car is repaired.

Many people are led to believe that you just need to regenerate a blocked D.P.F. but it is always very important to obtain the reason why its blocked in the first place so the D.P.F is not going to block again, as a blocked D.P.F. is usually highlighting an underlying problem on the vehicle which has caused it to block in the first place.

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