CVA Diesel Filter - What ports?

[greggron]

CAV Diesel Filter - What ports?

I have a CAV fuel filter but I am not sure what ports should be used. There are four. At the moment the set up as inherited is fuel from tank coming in at 4 and exiting to engine from 1. Can someone please advise if this is correct or should they be changed.

Thank you!

I have attached a picture of a similar filter for reference

 

[pvb]

You'll see that the ports have arrows moulded on them. The arrow shows the correct direction of flow. You should plumb it so that the fuel from the tank goes to a port with the arrow pointing in to the filter; and the filtered fuel going to the engine comes from a port with the arrow pointing away from the filter.

 

[nigelmercier]

You'll see that the ports have arrows moulded on them...

Could this be any clearer?

Port 2 or 3 in, 1 or 4 out. Perhaps the problem is the choice?

 

[Sandyman]

Could this be any clearer?

Probably not, but I have such a filter that does not have direction of flow arrows on it.
So ????

 

[greggron]

Thanks

You'll see that the ports have arrows moulded on them. The arrow shows the correct direction of flow. You should plumb it so that the fuel from the tank goes to a port with the arrow pointing in to the filter; and the filtered fuel going to the engine comes from a port with the arrow pointing away from the filter.

Good - thank you, that echoed my thinking that the original installation was incorrect. Hence the question. I will change right now.

I wonder why the marine engineer who apparently fitted it for the previous owner got that wrong...

 

[srm]

Good - thank you, that echoed my thinking that the original installation was incorrect. Hence the question. I will change right now.

I wonder why the marine engineer who apparently fitted it for the previous owner got that wrong...

There are people who strongly advocate reversing the flow. Their argument is that the muck is then in the centre of the filter and can be seen in the bottom bowl (if glass), however this also reduces the surface area available for filtration.

 

[prv]

There are people who strongly advocate reversing the flow.

Sure, but if the filter really is plumbed as described (1 and 4), then the fuel is going in and out without passing through the filter at all.

Pete

 

[pvb]

Sure, but if the filter really is plumbed as described (1 and 4), then the fuel is going in and out without passing through the filter at all.

Correct! The filter element would have lasted for ever.

 

[PCUK]

For filtration the fuel goes down through the centre of the filter and up the element. For water trap agglomeration it goes through the element first and out up the centre so that the droplets 'aglomerate' inside the element and fall to the bottom of the glass or aluminium bowl.

 

[pvb]

There are people who strongly advocate reversing the flow. Their argument is that the muck is then in the centre of the filter and can be seen in the bottom bowl (if glass), however this also reduces the surface area available for filtration.

The problem with reversing the flow is that the agglomerator function of the element (intended to help remove tiny droplets of water) is lost.

 

[lw395]

So the water is supposed to pass through the filter to get to the bowl?

 

[pvb]

So the water is supposed to pass through the filter to get to the bowl?

Yes, as the fuel goes through the filter medium, tiny droplets of water agglomerate into bigger droplets which can settle out.

 

[nigelmercier]

There are people who strongly advocate reversing the flow. Their argument is that the muck is then in the centre of the filter and can be seen in the bottom bowl (if glass), however this also reduces the surface area available for filtration.

Does the normal flow not do this then? [Later] Oops! I didn't read on. That's daft!

 

[prv]

Yes, as the fuel goes through the filter medium, tiny droplets of water agglomerate into bigger droplets which can settle out.

So the drops appear on the downstream side of the filter?

Pete

 

[pvb]

So the drops appear on the downstream side of the filter?

See this extract from an early CAV operator's manual...

 

[prv]

See this extract from an early CAV operator's manual...

Makes sense.

Pete

 

[greggron]

diesel weep

Thanks for all the advice. Have changed it to 3 & 1. That the fuel was passing straight through without being filtered accounts for the clod of gunge extracted from the engine end of the fuel pipe causing the blasted thing to grind to a halt.

Having now changed the filter, I now have to try and stop the damned thing weeping diesel!

 

[fisherman]

It has puzzled me for years, all filters seem to flow down through the element and out up the middle, so when I change the element the muck is sitting on top and the element is full of muck. Surely it would be better to filter up through, so the muck can drop off into the base? Similarly my water trap has a plastic cone over which the fuel enters, the muck sits on top instead of dropping to the bottom where I can drain it off, I have to shake it about to get the muck out, and eventually dismantle it when too bad. The cone is ideally shaped to stop anything getting up and over its edge to the exit, if reversed.

 

[JimC]

Having now changed the filter, I now have to try and stop the damned thing weeping diesel!

These CAV filters do seem to give a lot of trouble one way or another. Is there nothing better available?

 

[lw395]

These CAV filters do seem to give a lot of trouble one way or another. Is there nothing better available?

There are expensive racor ones, various cheap ones, and the transit van type with built in pump.
The CAV type is OK once you have the knack of getting it back together, which boatbuilders like to make a bit tricky!
The main thing is the elements are cheap and readily available.