PREVENTION OF DPF BLOCKAGE
• Correct and regular use of quality fuel additives.
• Correct use of oils and lubricants.
• Use of quality fuels.
• Correct driving technique and operating environment – i.e. short journeys will cause the DPF to block due to lack of time for successful regeneration to take place.
• Full, regular servicing of the vehicle is essential.
• Use of high quality replacement parts.
• Always use new gaskets and fittings and replace sensors where possible.
• The inappropriate use of sealing paste can damage substrates and lead to local hot spots.
• Follow manufacturer’s guidelines when resetting the ECU.
When a DPF can no longer be regenerated, a DPF warning light will illuminate on the dashboard. A garage would then look to perform a forced regeneration, dependent on the level of blockage.
• Regeneration should NOT be attempted on an adversely blocked DPF system without the prior removal and cleaning of components to reduce blockage.
•Recovery additives (chemical treatments) aid conversion by loading the DPF with products that help increase temperatures sufficient to oxidise soot. These “washing” methods require product knowledge and training if critical damage is to be avoided.
• Water-based cleaning can deteriorate DPF efficiency by 25-30% as it can remove the precious metal coating
When a DPF becomes blocked, the cause is very unlikely to be the DPF itself. The main reason for a blocked DPF is failure of regeneration. This is often caused by unsuitable driving
Unsuitable driving conditions → Incomplete regeneration → Inability to burn off soot → Blocked DPF
Other causes of a blocked DPF can be ash build-up or defects elsewhere within the engine. Replacing a blocked DPF without correct diagnosis of the genuine fault will only cause the new DPF to also become blocked!
DIAGNOSING THE FAULT
The following components are used in the control of soot combustion, therefore faults with any of these will either result in the DPF becoming blocked, or will lead the ECU to think the DPF is blocked when it is not. Ensure the following components are operating correctly before assuming a replacement DPF is required:
•Air Mass Meter
• EGR Valve
• Heater Plugs
• Swirl Flaps
• Lambda Sensor
• Exhaust Gas Sensor
• DPF Pressure Sensor
• Oxidation Cat
A DPF will find it impossible to convert soot into carbon dioxide once it has been impaired by excessive regeneration cycles, ageing (ash accumulation) or due to inappropriate cleaning methods that have damaged the coating. In such cases, replace with a high quality DPF.
Some vehicle manufacturers recommend that the DPF is replaced from 60,000 miles.