Wednesday, Jan 18, 2012 at 23:36
Lindsay is correct in saying a filter will filter better when blocked.
The trouble starts when the filter, either petrol or diesel is left there long enough that the filter medium,ie the filter material itself, starts to degrade and lets through lumps of filter, water and dirt.
Donaldson filters site makes mention of filter degradation and to avoid it.
Many makes say 18-24 months is maximum life of a fuel filter actually immersed in fuel.
If the first filter was doing its job then all is well but when the degradation starts then it will cause further problems again and again if not changed.
As the owner of diesels Lindsay will have changed his filters and not got to the point where degradation of the filter medium happened.
The function of a filter is to stop contaminants and will block eventually. This will give symptoms of fuel starvation, not of component failure and component blockage.
This vehicle was driving until it was stopped with blockages of components down stream of the filter. The idea is to change the filter before this happens.
It is highly possible the filter has degraded and all the crap has now gone to the fuel system. It worked well when the filter was doing its job but now there is a repeat performance which theoretically can't happen with a properly functioning filter.
Although its about a petrol engine here. The mention of diesels came into it to highlight the fact that some of them, many makes involved here, can be driving along happily and suddenly destroy their injection pump and injectors. The common item here is NOT changing the filter as necessary to avoid trouble.
Many people who have had their vehicles serviced by dealer/mechanic have had trouble.
I can't recall such failures happening to people who diligently service their own vehicles.
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