Filters for dumbos. How fine is a CAV

[pcatterall]

Agood week since our last filter session. Somebody mentioned That having two CAV filters was an issue as they were equally 'coarse'.
I have a water seperator with drain then a CAV with glass bowl and drain then another CAV without bowl.
In my ignorance I thought that the filters inside the two CAVs were of different coarseness.
IE say around 15 for the first filter then 5 for the fine filter, I expected that when I ordered the filter for the engine filter it would be different than that for the primarry filter.
The response made last week leads me to wonder about this.
Can someone please enlighten me? ( I know there are others who could use a lesson!!)
Why dont they supply info about the filter coarse/fineness on the box?

 

[rob2]

The Delphi HDF296 is quoted on the Thornycroft site as 5-7micron. Also equivalent to:

Crossland 522
Fram C1191
Lister 351-29760
Coopers AZF015
Kubota 15451-43560
Volvo 233628,233666284,263628,3473910/-2, etc

I tried the Delphi website but that is pants, can't look up parts without a vehicle make model and type.

I bought a pack of twenty filters when news of the bug broke. Of course, I haven't used them yet! Good price though...

Rob.

 

[theoldsalt]

I don't know what all the fuss is about with fuel filters.

I have a standard glass bowl water trap between the tank and the lift pump and a Delphi 296 between the lift pump and the injector pump.

I have never had engine problems caused by inadequate fuel filtration. I have a Thornycroft T80.

 

[paulm299]

CAV 296 for example filters to 5-7 microns . When I do it the engine manufacturer usually states that 2 filters are fitted with no mention of coarse or fine . Is a Crossland filter different ?

 

[GrahamM376]

I don't know what all the fuss is about with fuel filters.

I have a standard glass bowl water trap between the tank and the lift pump and a Delphi 296 between the lift pump and the injector pump.

I have never had engine problems caused by inadequate fuel filtration. I have a Thornycroft T80.

That's what our T80 had and I always thought it strange that the primary filter (first in line) was the gauze in the fuel pump.

 

[theoldsalt]

GrahamM376,

As you say the first filter in the fuel line is the gauze in the lift pump.

I have replaced my mechanical lift pump with an electric pump for which I have a spare pump filter element but never had to fit is as the one in the pump never seems to be dirty. I think that is because it is designed to stop only large particles and I keep my tank as clean as possible. The small ones go through the lift pump having no effect and are collected in the Delphi 296.

 

[neil1967]

theoldsalt

So does your electric 'lift' pump pressurise your fuel system and remain energised all the time the ignition is on? I presume that so long as the pump can supply sufficient fuel to keep the high pressure pump supplied, it does not have to be anything special. I guess that having an electric pump, which could be quite close to the fuel tank, makes bleeding the system alot easier?

Neil

 

[theoldsalt]

Neil,

Yes, since fitting the electric lift pump the engine starts sooner as the system is pressurised as soon as the ignition is stitched on. You don't have to wait for the engine to turn over to get pressurised fuel to the injector pump.

This has the added benefit that bleeding is much easier. Just crack a union or open a bleed valve and turn on the ignition. Again no cranking of the engine or leaning over the engine to operate the manual lever on a mechanical lift pump (if there is one fitted).

I can hear the electric lift pump working as soon as the ignition is switched on. It ticks very rapidly at first and slows as the pressure builds up. It never completely stops even without the engine running as fuel returns to tank via the spill loop.

 

[Jim@sea]

I put a new CAV Filter Unit in which also had the Glass Bowl underneath.
The other thing I did was to use a jig saw cutting a section out of the GRP above the fuel tank so that the tank can be totally removed for cleaning. (before I cut the panel out I placed brackets on the GRP, drilling holes, so that I could replace the panel, 4ft x 6", being held in place by the brackets easily, so when the boat is winterised I am taking the tank home and stored in a dry area) (No winter condensation for me then)
You would not believe the krap which was in the tank.
Certainly making sure that the tank is totally clean is just as important as upgrading filters.
(Being paranoid saves money)

 

[gavin400]

I have a gravity feed fuel tank (with no access for cleaning), and the outlet comes straight out the bottom of the tank so it is always liable to pick up debris from the bottom of the tank.

I'm considering a new tank with a top outlet (so that the fuel supply pipe is higher than the bottom of the tank), this feeds a CAV/water seperator and then the engine - my question is, would my Volvo md1 be able to pump fuel to itself with such a system, or would I need a lift pump to get the fuel from the tank to the CAV?

 

[pvb]

... my question is, would my Volvo md1 be able to pump fuel to itself with such a system, or would I need a lift pump to get the fuel from the tank to the CAV?

Yes, the engine's pump will cope fine.