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Can anyone tell me which way the fuel flows through a 296 filter? It's the version with 4 ports in the head, two of which get blanked off. Assuming that it's connected properly to the other two ports, does the fuel flow through the filter before reaching the bottom of the housing or does it flow straight to the bottom of the housing before passing through the filter?

 

I'd always assumed it went to the bottom of the housing first but something I read on another forum suggests that it passes through the filter first (and someone there suggests that it's better to connect it back to front so that the filter isn't exposed to any water).

 

I ask because I've noticed that the fuel flows out of the drain cock at the bottom of the housing relatively slowly if I loosen it to check for water, and I'm wondering whether this is because it has to pass through the filter first (which may indicate that I need to change the element). If not it would suggest that maybe there is still something unwanted in the pipe.

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If its a genuine 296 or reputable pattern one then its a pocket filter where a long strip of filter material is folded to form along pocket and then wound up like a swiss roll. In these the fuel flows from the top, down through the pocket and at some point sideways through the filter material and exits the bottom via louvres that give it a slight spin. Then up the centre and on to the engine.

 

If its a non-genuine one it may be a pleated filter where the filter material is folded like a concertina and then formed into a circle. In these the fuel flows down the outside and at some point sideways through the filter material straight into the centre where it turns through 90 degrees to flow up and out of the filter.

 

In my view always use a pocket filter. They gave a greater "dirt capacity" and makes it harder for a small water or dirt droplet to pass on to the injector pump.

 

Note: Many well known name 296 filters are pleated. I use Mann or genuine 296s. The types are interchangeable according to the individual manufacturers.

 

 

Edited to add. Unless you are pumping the fuel through the filter then you are relying on the head of fuel to push it through the system and filter so on a typical boat it would not gush out, only dribble. You could improve the flow a bit if you let air into the top of the filter but then you would have to bleed the system.

Edited by Tony Brooks
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If its a genuine 296 or reputable pattern one then its a pocket filter where a long strip of filter material is folded to form along pocket and then wound up like a swiss roll. In these the fuel flows from the top, down through the pocket and at some point sideways through the filter material and exits the bottom via louvres that give it a slight spin. Then up the centre and on to the engine.

 

AAAaaarrghhh - the exact opposite of the diagram!

 

I have a CAV filter head here somewhere, I know I've been falling over the wretched thing for weeks now. Do you think I can find it?

 

Richard

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Yes there's two opposite answers for me! But Tony's reply and edit suggest that I shouldn't be worried at getting a dribble rather than a gush.

 

Sadly the only filters I've been able to get while on my travels have been the cheap folded ones. I'll maybe get some of the better ones over the winter.

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Pocket filter - down through the body of the filter, out the bottom and back up the centre.

 

Pleated filter - down the outside of the pleated filter, sideways through the pleats to the centre and back up the centre.

 

All 296s should have a small O ring on the "nose" in the centre of the filter head so that whichever type of filter can seal to the nose and stop dirty fuel getting into the centre without passing through the filter.

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If its a genuine 296 or reputable pattern one then its a pocket filter where a long strip of filter material is folded to form along pocket and then wound up like a swiss roll. In these the fuel flows from the top, down through the pocket and at some point sideways through the filter material and exits the bottom via louvres that give it a slight spin. Then up the centre and on to the engine.

 

If its a non-genuine one it may be a pleated filter where the filter material is folded like a concertina and then formed into a circle. In these the fuel flows down the outside and at some point sideways through the filter material straight into the centre where it turns through 90 degrees to flow up and out of the filter.

 

In my view always use a pocket filter. They gave a greater "dirt capacity" and makes it harder for a small water or dirt droplet to pass on to the injector pump.

 

Note: Many well known name 296 filters are pleated. I use Mann or genuine 296s. The types are interchangeable according to the individual manufacturers.

 

 

Edited to add. Unless you are pumping the fuel through the filter then you are relying on the head of fuel to push it through the system and filter so on a typical boat it would not gush out, only dribble. You could improve the flow a bit if you let air into the top of the filter but then you would have to bleed the system.

There is an example I posted at http://www.canalworld.net/forums/index.php?showtopic=62795&p=1209815

 

filter.jpg

Edited by ditchcrawler
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I doubt they ever did make them but I would expect to get a Delphi/CAV/Lucas branded one from a fuel injection specialist. I know the Mann & Hummel equivalent is a pocket filter and I have seen others. The makes from what used to be Filtre Auto (Coopers, Fram, Purolator etc.) are as far as I know all pleated.

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I tried to get a Delphi one, as that was what was there originally, but was told that Delphi don't do them any more. Is that info correct?

 

Hmm! - bought genuine Delpi 296 filter element the other day through eBay, assuming that's what you are referring to.

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I thought Blackrose was asking a stupid question until we were educated by Tony B. I will use my spare Coopers filter and seek something better next time. Fuel filters are generally so cheap that there is little advantage to buying the cheapest. I doubt I can persuade my local Motor Factor of the difference but I am certain he will be happy to supply an AC/Delco rather than a Coopers.

 

Alan

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To add both types (all) of fuel filter also act as agglomerators that agglomerate tiny water droplets into larger ones that then drop into the bottom of the filter. If you reversed the flow through a pocket filter you would end up with water trapped within the body of the element with a much better chance of passing it to the injector pump - not a very bright idea. If you reversed the flow through a pleated filter large drops of water may fall into the bowl but the smaller ones will, after agglomeration, will end up trapped in the element on what would then be the clean side. Again not so bright.

 

Moral - don't trust everything you read on the internet, especially forums, unless the poster has some history and you have decided they know what they are talking about.

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I certainly wouldn't trust anything posted by someone who hadn't a proven track record, on any forum especially this one! Fortunately there are some proven experts here.

 

The poster in question was assuming that after reversing the direction of flow, agglomeration would still take place in the bowl and would therefore prevent the element being, as he put it, "exposed to the water in the fuel". I think I can see where he's coming from, but it seems that he got a bit confused and hence I got a bit puzzled; I just found his comments while I was trying to find out whether the drain tap was before or after the filter, particularly as the diagram on Tony's excellent site didn't resolve very clearly on the tiny screen I was using.

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I finally ran it to ground, hiding in my work bag

 

Underside-1.jpg

 

This is the underside of a modern CAV filter head. The inlets are at the upper connections, the outlet are the lower ones and connect to the central hole. The large groove is where the seal sits that seals the filter cartridge to the head

 

Underside-2.jpg

 

Here you can see the drilling that connects into the housing. It is connecting to the same space as the bleed hole, so bleeding the filter head bleeds the inlet side of the filter. On the central stub is the O ring that seals the inlet and outlet sides from each other by fitting into the central hole of the cartridge. This needs to be changed when you swap a filter. It does help too, as it will often hold a filter in place while you search for lost seals, spanners, bolts, bowls...

 

Top.jpg

 

This is the top of the filter. Here we can see the bleed hole connecting to the bleed screw. This is a later style filter and seals the centre bolt with an O ring. It slips onto the bolt and is compressed into the countersunk seating. Earlier heads have a flat face here and use a copper washer

 

The filter heads fitted to some Lister engines have the ports swapped about, the inlet and outlet being transposed. This makes replacing a head a bit of a problem - I'm looking for one

 

Richard

Edited by RLWP
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I certainly wouldn't trust anything posted by someone who hadn't a proven track record, on any forum especially this one! Fortunately there are some proven experts here.

 

The poster in question was assuming that after reversing the direction of flow, agglomeration would still take place in the bowl and would therefore prevent the element being, as he put it, "exposed to the water in the fuel". I think I can see where he's coming from, but it seems that he got a bit confused and hence I got a bit puzzled; I just found his comments while I was trying to find out whether the drain tap was before or after the filter, particularly as the diagram on Tony's excellent site didn't resolve very clearly on the tiny screen I was using.

 

Sorry about the diagram, the quality is a leftover from when I put the site together when almost all people were on dial up broadband so the image files needed to be a small as possible. I anticipate my days working for the magazine are numbered so when/if that comes to an end the site will come down to save money so I do not feel it is worth going through the site adding higher resolution images.

 

All fuel filters will act as agglomerators so the filter material should be water resistant. Unless I have been mislead about agglomerator operation teh chaps concerns are a non-issue.

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