Cav fuel filters

[Dr Bob]

Had our boat 2 years now. Last winter I had RCR do an engine service. They drained the contents of the primary fuel filter/agglomerator/wotever only.  Today I had them in again to do a service and they dismantled the 'cav'  unit. I knew it was not a filter - previously told it was a water separator. When they took it apart, there was no cone or funnel in it. Just the casing! So its just been operating as a simple sedimentation device!

So, what should I put in its place? On our lumpy water boat I put a Racor spin on filter as I wanted to be able to change it in the dark in a force 9 (.....and that did happen in the Messina straights) but it seems a bit of overkill on a NB.

What is the current thinking of what I use as the one unit to protect the main engine diesel filter? Is it a water separator or is it a 30 micron filter? I have read the 30 micron filter can get blocked easily whereas the separators just throw the crap down to the bottom of the bowl to be run out.

Never had a problem with fuel on this boat (or the other one - the Messina straight problem was motor sailing into a force 9 and the boat heeling too much so air was sucked into the filter system) so the fuel is pretty clean.

It would be nice to have a see through bowl at the bottom and looks like the fuel guard filters are ok on the BSS - but expensive. I need one feed in and two feeds out (for the engine and for the eberpacky thingy)

[RLWP]

14 minutes ago, Dr Bob said:

Never had a problem with fuel on this boat

There's your answer

[ditchcrawler]

I have one of these before the engine filters. One thing to note is the construction of the actual filter bit, its not the same as any equivalents I have bought in the way the element is wound, Tony Brooks will explain better that me https://www.asap-supplies.com/cav-type-fuel-filter-water-separator-302006

 

 

Edited April 3, 2019 by ditchcrawler

[Sea Dog]

When searching for such a unit to add to my boat a few years ago I fitted a cheap metric CAV/Delphi spin on filter head  and chose a Mann & Hummell WDK725 screw on filter which has a metal drain plug to allow me to take a sample and/or drain off any water.  Touch wood, I always get clear and bright diesel!  Finding the specifications for filters (other than thread and dimensions) is the devil's own job though and, try as I might, I can't tell you what they were, however, I must've found it somewhere cos I was looking for a particular filter size in microns and the ability to separate water.

 

Incidentally,  your Eber ought to have its own pick up from the tank a bit higher up than your engine supply take off.  This is so it can't use fuel down to a level that leaves you with insufficient fuel to run your engine, thus removing the potential of your heating accidentally leaving you stranded.

[Dr Bob]

2 hours ago, RLWP said:

There's your answer

Yep, I guess you are right, but something will be better than nothing.

[Dr Bob]

2 hours ago, ditchcrawler said:

I have one of these before the engine filters. One thing to note is the construction of the actual filter bit, its not the same as any equivalents I have bought in the way the element is wound, Tony Brooks will explain better that me https://www.asap-supplies.com/cav-type-fuel-filter-water-separator-302006

 

 

Thanks Brian. Is it a filter or is it a water separator? The link just shows the overall unit and I am not sure if its better to have a filter or a water separator.....and then if the filter is better, what sort of filter is the best?

2 hours ago, Sea Dog said:

When searching for such a unit to add to my boat a few years ago I fitted a cheap metric CAV/Delphi spin on filter head  and chose a Mann & Hummell WDK725 screw on filter which has a metal drain plug to allow me to take a sample and/or drain off any water.  Touch wood, I always get clear and bright diesel!  Finding the specifications for filters (other than thread and dimensions) is the devil's own job though and, try as I might, I can't tell you what they were, however, I must've found it somewhere cos I was looking for a particular filter size in microns and the ability to separate water.

 

Incidentally,  your Eber ought to have its own pick up from the tank a bit higher up than your engine supply take off.  This is so it can't use fuel down to a level that leaves you with insufficient fuel to run your engine, thus removing the potential of your heating accidentally leaving you stranded.

Thanks Sea Dog. That sounds a fairly simple solution. I like the spin on bit - much easier to do. The M&H WDK725 looks like it is used on a Merc. Where did you get the Cav/Delphi spin on filter head. I will do a search. I assume the pipe connections into my current head will be ok for a new Cav type head.

Ok on the pick up for the eberspacky thingy. ......but I wont be changing it! I guess that the tank will be pretty full when it is cold and I need to run the heater. Good point though. I'd not thought of that.

[Slim]

My experience of changing CAV 296 filters (in a gale) was in the Bay of Biscay. Good fun.

My understanding of the filter unit shown is that fuel flows into it, any water drops to the bottom allowing 'neat fuel' to pass through he element and on to the engine. My CAV filter has a water separator with the filter alongside all in one unit. In reality in 20 years + I've never found a drop of water anywhere in the fuel system. I do 'hoover' out bottom of the fuel tank once a year using my Pela  

 

[ditchcrawler]

10 minutes ago, Slim said:

My experience of changing CAV 296 filters (in a gale) was in the Bay of Biscay. Good fun.

My understanding of the filter unit shown is that fuel flows into it, any water drops to the bottom allowing 'neat fuel' to pass through he element and on to the engine. My CAV filter has a water separator with the filter alongside all in one unit. In reality in 20 years + I've never found a drop of water anywhere in the fuel system. I do 'hoover' out bottom of the fuel tank once a year using my Pela  

 

I have that on the engine, but I remember Tony saying its better to have one off engine so it dosen't get shaken about.

[Slim]

1 minute ago, ditchcrawler said:

I have that on the engine, but I remember Tony saying its better to have one off engine so it dosen't get shaken about.

Actually mine is off the engine between the lift pump and the injector pump. 

[Tony Brooks]

15 hours ago, Dr Bob said:

Had our boat 2 years now. Last winter I had RCR do an engine service. They drained the contents of the primary fuel filter/agglomerator/wotever only.  Today I had them in again to do a service and they dismantled the 'cav'  unit. I knew it was not a filter - previously told it was a water separator. When they took it apart, there was no cone or funnel in it. Just the casing! So its just been operating as a simple sedimentation device!

 

 

Thought I had posted this last night but obviously not.

 

Are you sure there is not a plastic cone fitted tight under the top. Modern practice no longer uses the intermediate body section with a metal cone in it. The plastic cones can be hard to spot if you cant get your head down to that level but easy enough to feel.

 

 

[Dr Bob]

49 minutes ago, Tony Brooks said:

 

Thought I had posted this last night but obviously not.

 

Are you sure there is not a plastic cone fitted tight under the top. Modern practice no longer uses the intermediate body section with a metal cone in it. The plastic cones can be hard to spot if you cant get your head down to that level but easy enough to feel.

 

 

Thanks Tony. Not sure on the plastic cone. The RCR guy was down the hole so I only saw the bowl. It looks 2004 vintage as per the boat and it looked like there were 'lugs' in the bowl to support a cone.

In previous threads IIRC, you have suggested a water agglomerator and a filter in line (going back a few years). Do the Cav type filters separate the water and then do the filtering? In my time on the lumpy water boat and this one I have never seen any water in the bowls and we dont put any additives in the fuel. We always fill it up and keep it topped up in winter.

I am tempted by the Cav/Delphi screw on conversion unit and then use the screw on filters, but these dont have bolts on the bottom to draw off water......but if there isnt any water? Maybe then just change the filter every 200 hrs or so. I cant seem to find any water agglomerators that havent got a filter. Can anyone see a link?

An alternative is the fuelguard stuff where there is a reusable filter but then that is more money.

I did come across this link which is just too much information!

http://www.lena.geoffrichings.co.uk/sail_site/cav.html

I'll read it again. Sea dogs solution sounds better by the day.

[Tony Brooks]

Sedimetors (the ones with the cone) separate the larger dirt and water particles but ;leave about 20% of fine water droplets in the fuel (From the CAV booklet) where as agglomerators deal with the whole lot (we hope). The problem is that the pores in the filters used in agglomerators are very small so clog far more readily than the large gap around the sedimento's cone.  In normal use with a CLEAN tank this is probably not a major consideration but once the possibility of bug arises my view is that it would be best if a difficult to block fuel cleaning device came before an easier to block one are best.

 

As far as I know all fuel filters agglomeratee the water droplets to a lesser or greater extent but they all do it via the small pores in the filter. This is why the pocket filters (Swiss roll type) are better as agglomerators than pleated filter. They have a far greater filter surface area so take longer to block.

 

I would not read too much into the lugs in the casting because it costs money to change the die and the extra  metal needed to form the lugs is so small it is unlikely to be economic to make the change.

 

If you really do not have a cone in it then just fit a CAV 296 type filter but keep the tank clean. This will involve you in one extra filter to change though but they only cost a very few pounds.

[dmr]

40 minutes ago, Dr Bob said:

Thanks Tony. Not sure on the plastic cone. The RCR guy was down the hole so I only saw the bowl. It looks 2004 vintage as per the boat and it looked like there were 'lugs' in the bowl to support a cone.

In previous threads IIRC, you have suggested a water agglomerator and a filter in line (going back a few years). Do the Cav type filters separate the water and then do the filtering? In my time on the lumpy water boat and this one I have never seen any water in the bowls and we dont put any additives in the fuel. We always fill it up and keep it topped up in winter.

I am tempted by the Cav/Delphi screw on conversion unit and then use the screw on filters, but these dont have bolts on the bottom to draw off water......but if there isnt any water? Maybe then just change the filter every 200 hrs or so. I cant seem to find any water agglomerators that havent got a filter. Can anyone see a link?

An alternative is the fuelguard stuff where there is a reusable filter but then that is more money.

I did come across this link which is just too much information!

http://www.lena.geoffrichings.co.uk/sail_site/cav.html

I'll read it again. Sea dogs solution sounds better by the day.

If you want a spin on conversion then the HDF496 filter does have a drain at the bottom. Its a plastic drain but easy to replace with a flanged head bolt and washer. Its a lot deeper than the 296 so more capacity, but obviously needs more height to accommodate it. Its a whole lot quicker to change than the 296 type.

 

If you want a good trustworthy 296 filter element then Racor do them, but they cost a fair bit more than the bog standard ones.

 

I have a spin on 496 as the first filter, its under the floor so access is a bit restricted, then a standard 296 as the second filter on the engine, but with a Racor element.

 

I have cut the bottom from a large coke bottle (the old 2 litre version?) and this just fits over the 296 (from below) which usually avoids spilling a load of diesel when I change the filter.

 

..............Dave

[Tony Brooks]

2 minutes ago, dmr said:

I have cut the bottom from a large coke bottle (the old 2 litre version?) and this just fits over the 296 (from below) which usually avoids spilling a load of diesel when I change the filter.

 

..............Dave

 

Good tip Dave, never would have thought of that.

[ditchcrawler]

1 hour ago, Tony Brooks said:

 . This is why the pocket filters (Swiss roll type) are better as agglomerators than pleated filter. They have a far greater filter surface area so take longer to block.

 

 

 

As per my photo in 

 

[Dr Bob]

Ok, with all your inputs I have now worked out a way forward. I am looking to get one of these:

https://www.asap-supplies.com/spin-on-fuel-filter-replacement-kit-for-cav-filters-302040

 

The blurb says it has four 1/2" UNF female ports.

The spin on filter is

https://www.asap-supplies.com/spin-on-engine-fuel-filter-element-103423

Which says it is an M16 * 1.5. This is the size of many of the spin on filters so gives me a good choice  from the following link

https://www.inlinefilters.co.uk/Filters-Fuel/SpinOn/M16x1.5

I can get one with a metal drain tap and I think use the Mann filter that Sea Dog suggested earlier.

 

So, it has UNF ports but a metric fitting for the filters? Is this right?

 

Below is an image of my current head. Any thoughts on the size of the inlet/output ports on this. Can you tell from the size of the spanners needed? It would be good if my current brass fittings can screw straight into the new head.

[peterboat]

9 minutes ago, Dr Bob said:

Ok, with all your inputs I have now worked out a way forward. I am looking to get one of these:

https://www.asap-supplies.com/spin-on-fuel-filter-replacement-kit-for-cav-filters-302040

 

The blurb says it has four 1/2" UNF female ports.

The spin on filter is

https://www.asap-supplies.com/spin-on-engine-fuel-filter-element-103423

Which says it is an M16 * 1.5. This is the size of many of the spin on filters so gives me a good choice  from the following link

https://www.inlinefilters.co.uk/Filters-Fuel/SpinOn/M16x1.5

I can get one with a metal drain tap and I think use the Mann filter that Sea Dog suggested earlier.

 

So, it has UNF ports but a metric fitting for the filters? Is this right?

 

Below is an image of my current head. Any thoughts on the size of the inlet/output ports on this. Can you tell from the size of the spanners needed? It would be good if my current brass fittings can screw straight into the new head.

Bob I have a fuelguard on mine, it works well is clear and will pass the BSS, it has a washable filter in it. I fitted it a few years ago now, and wash it out yearly, its surprising how much crap it stops. Mine is fitted straight out of the tank and before the fuel pump and the main filters on the diesel engine [all that removed now apart from the fuel guard which prefilters the kero before the whispergen eats it]

[Dr Bob]

1 hour ago, peterboat said:

Bob I have a fuelguard on mine, it works well is clear and will pass the BSS, it has a washable filter in it. I fitted it a few years ago now, and wash it out yearly, its surprising how much crap it stops. Mine is fitted straight out of the tank and before the fuel pump and the main filters on the diesel engine [all that removed now apart from the fuel guard which prefilters the kero before the whispergen eats it]

Thanks Peter,

I looked at those and they do look good. The snag is that the ones I looked at only had two ports, one in, one out. I need two out - one for the engine and one for the eberspakcy thingy. I looked at breaking the line into the current CAV unit and putting a fuel guard in there so leaving the current CAV in place, but there is not enough pipe to do this so would need a bit of work (ie Faffing). The spin on conversion head above seems the minumum faffing option to get a spin on filter.

 

eta Here's the pic I should have posted earlier.

Edited April 6, 2019 by Dr Bob

[ditchcrawler]

The only thing that bothers me with washable filters is the risk of contaminating the down stream side of the filter when cleaning. Probably not a problem for people posting here as they would be taking great care, but there are a lot of boaters who read the add and may not be so aware of the need for cleanliness with diesel in injector systems

[David Schweizer]

On Helvetia we just one fuel fiklter which was the original equipment CAV fuel filter, attached to the engine. In twenty years we never had any fuel problems, and each service, I poured a jar full of clean fuel out containing no water or sediments.

 

 

 

Edited April 6, 2019 by David Schweizer

[peterboat]

19 minutes ago, ditchcrawler said:

The only thing that bothers me with washable filters is the risk of contaminating the down stream side of the filter when cleaning. Probably not a problem for people posting here as they would be taking great care, but there are a lot of boaters who read the add and may not be so aware of the need for cleanliness with diesel in injector systems

I had two more filters down stream of it, I fitted it because there was no filter before the fuel pump, guess what happened to the first fuel pump!!!

[ditchcrawler]

5 minutes ago, David Schweizer said:

On Helvetia we just one fuel fiklter which was the original equipment CAV fuel filter, attached to the engine. In twenty years we never had any fuel problems, and each service, I poured a jar full of clean fuel out containing no water or sediments.

 

 

 

I think you need a new V belt on there

[Sea Dog]

2 hours ago, Dr Bob said:

Ok, with all your inputs I have now worked out a way forward. I am looking to get one of these:

https://www.asap-supplies.com/spin-on-fuel-filter-replacement-kit-for-cav-filters-302040

 

The blurb says it has four 1/2" UNF female ports.

The spin on filter is

https://www.asap-supplies.com/spin-on-engine-fuel-filter-element-103423

Which says it is an M16 * 1.5. This is the size of many of the spin on filters so gives me a good choice  from the following link

https://www.inlinefilters.co.uk/Filters-Fuel/SpinOn/M16x1.5

I can get one with a metal drain tap and I think use the Mann filter that Sea Dog suggested earlier.

 

So, it has UNF ports but a metric fitting for the filters? Is this right?

 

Below is an image of my current head. Any thoughts on the size of the inlet/output ports on this. Can you tell from the size of the spanners needed? It would be good if my current brass fittings can screw straight into the new head.

That blurb for that head does say UNF threads on the ports so it might well just accept your current fittings...  as long as they're UNF of course (pretty likely, I'd have thought). You'll be needing a blank for the unused port and copper washers all round.  It also has an M16 thread so the spin on filters to fit are widely available. I think I bought from a little outfit (possibly recommended on here - I may recognise the name) and got 2 blanks in the head already, but I wouldn't swear to it. Makes sense though as most folk are going to be using it "1 in, 1 out" I'd have thought.

 

There are many ways to skin this cat, but if you're gonna go the same way I did, I bought my WDK725s from eBay and Amazon at about a tenner Inc postage - other places were cheaper, but the postage was a killer.  I'm sure you could also get the things from a local commercial motor factor.  The metal drain plug makes it very easy to take a fuel sample so you can see what's coming out of your tank or to drain any water.

[Guest]

1 hour ago, ditchcrawler said:

I think you need a new V belt on there

It's one o' them invisible ones wot they used to make. You don't see 'em now.

[Dr Bob]

10 minutes ago, catweasel said:

It's one o' them invisible ones wot they used to make. You don't see 'em now.

Where did you see them then?