Fuel Filter question

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Tim Lee

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Morning All
I am seeking some advice, again!
My 30 year old Volvo Penta MD11C appears to have been retro fitted with an additional fine fuel filter in addition to the main fine filter mounted close to the engine. This additional filter is not a pre filter/water separator type but a typical fine filter.
The whole assembly is a bit knackered and leaky so I am going to remove it and rely on the main filter solely. My questions are thus:
Does this additional filter really offer any extra 'protection'? When I have serviced the engine, this filter has always collected all the muck with the main filter being totally clean. Is it just an extra complication that is more likely to leak/get blocked than offer any real assistance?
Should I really be seeking to replace it with a proper pre filter/water separator rather than just remove it?
Thank you:confused:
 
Could it be that the previous owner found the main filter hard to get at and fitted one that he could reach easily? You should certainly have a proper filter/separator.
 
I suppose that is possible, although I find this extra filter equally inaccessible!
By the look of it, it was fitted a long time ago. Presumably the separator type filters weren't around 30 years ago?
 
The engine filter is usually designed to remove particles in the 2 micron range while the upstream filter is designed to remove gunk in the 10 - 30 micron range. If the engine pumps more fuel through the filters than is consumed and returns the excess back to the tank having the excess filter is desirable since you have much more filtering surface area than if you rely on the engine's filter only. If you use a lot of fuel, more filters are desirable, or if the tank is dirty with asphaltine and bacterial gunk then an additional filter is desirable.

Generally you only see relianace on the OEM filter when the engine is quite small, the amount of fuel used isn't great, and the tanks are kept clean. The last is virtually impossible since all diesel has asphaltine particles that will settle out, water does condense providing a home for bacteria to do their thing, and most tanks have no clean outs.

If you're looking for a project, remove the existing primary filter and replace it with a suitable size Racor type with a transparent bowl so you can see what's going on.
 
I always use a Mr Funnel filter before the fuel goes in the tank as well, not sure about microns but it filters out any water in the fuel...
 
Tim Lee said:
Morning All
I am seeking some advice, again!
My 30 year old Volvo Penta MD11C appears to have been retro fitted with an additional fine fuel filter in addition to the main fine filter mounted close to the engine. This additional filter is not a pre filter/water separator type but a typical fine filter.
The whole assembly is a bit knackered and leaky so I am going to remove it and rely on the main filter solely. My questions are thus:
Does this additional filter really offer any extra 'protection'? When I have serviced the engine, this filter has always collected all the muck with the main filter being totally clean. Is it just an extra complication that is more likely to leak/get blocked than offer any real assistance?
Should I really be seeking to replace it with a proper pre filter/water separator rather than just remove it?
Thank you:confused:
Click to expand...

For a sound setup you should have a water separator type filter first in line, in addition to the main filter on the engine.

Access is something else - perhaps you can ditch the current aged item, remake the line carefully to prevent air ingress and replace in another more accessible position?

Chucking away apparently clean filters is the best news from your point of view - cruddy filters are a srious warning of trouble ahead!

With variable quality fuels these days, you never know when you'll take some water / bug on board with the diesel and be grateful the filter stopped it getting any further.

An engineer friend told me long ago to chuck out used fuel filters first, before changing the oil filter. Clean fuel is a must!

PWG
 
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