Seems to me the '04-'06 T1N & NCV3 OEM filter setups are adequate for all usual contaminates EXCEPT water. Water separation is more difficult for these systems, which utilize an in-tank low pressure fuel pump, because the shear and turbulence in the pump will tend to reduce water droplet size and promote a water-in-fuel emulsion. So, IMHO, merely adding more OEM-style filters won't solve the water issue here. I think a different water-in-fuel solution needs to be found for these systems.
Since water contamination most probably originates somewhere in the supply chain, the KISS solution would be to make sure any fuel put in your van's tank is free of water. It's easy to tell visually whether water is present (
http://www.wsbindustries.com/presentation_wsb_fuel_guide.pdf), so all that needs to be done is to pump a small amount of fuel into a clear container and look at it. If it's off-color (fluorescent green) or cloudy, it's water-contaminated - put the nozzle back and move on to a different station.
That's the KISS solution. Any other solution (dispersion-breaking filters, absorbing filters, etc.), while possible will be much more complex.
I'm no expert.
According to the DMax article author, a pre-filter does help the existing water separation capability to do the job.
Who is really going to sample their fuel at pump every time? How do you properly dispose of the sample that you pulled? A funnel back into the tank? It all sounds like a sloppy inconvenient process which will quickly be abandoned by most operators/owners.
The Mahle KL313 Pre-filter concept.
According to the DMax author a pre-filter helps.
The initial cost for the Mahle filter, connecting hose, clamps, and 2 each hose unions will likely be under $40.00 total.
The filter can be supported with a bracket formed by perforated strap or other metal. The filter can be clamped to the bracket using a worm drive hose clamp. There is room in my OM647 engine bay.
My service schedule.
Initially change out the existing OEM fuel filter [to a Mahle KL228/2D] and the new added KL313 pre-filter at the same time. After the pre-filter is in service then change that on whatever service schedule that the owner feels appropriate. Leave the original OEM filter alone.
The Mahle filter is about $25.00 per change. In the TIN the filter will be up where accessible. It will only require R&R of 2 each hoses for the change. The cost avoidance of not needing to change the more expensive OEM WIF filter will pay for the pre-filter.
On the OM612 engine just changing the added pre-filter means that the problematic air leak filter system is disturbed less often. Remember, 2 hoses for the pre-filter.
Gelling in the Mahle pre-filter. There is more risk of gelling with any added pre-filter. What
cheaper added aftermarket filter system will have fuel pre-heat built in? I believe that I can safely answer "None".
I'm actually considering adding the pre-filter to my 2006. I hate the access to the fuel filter now. Having a fuel filter accessible and only needing to deal with 2 hose connections is attractive.
A self designed aftermarket filter may be more effective (or maybe not...), but it is expensive and not easily installed.
I see no serious drawbacks to installing a Mahle pre-filter. I actually believe that there is benefit.
vic
P.S. - Check your local laws/ordinances as to whether pumping fuel into a glass container is legal. I believe that it is against the law all across the USA. You might get a reaction if some Homeland Security zealot decides to intervene.