Cav fuel pre filters, yes? or no?

[macca]

Today I decided to change my fuel filters, mine is a '05 4.2 TD.

The standard filter has a genuine Nisson product fitted, and I also use a CAV prefilter.

The ute has travelled 26000 klm since the CAV was installed and the Nissan was replaced at the same time.

The CAV is before the Nissan filter.

Take a look at these...

#1 Both on the bench
#2 CAV
#3 CAV close up, note sludge
#4 CAV side view
#5 Nissan side view

I am suprised at the filth on the CAV and how clean the Nissan one is.

[nissannewby]

The proof is in the pudding aye.

[GeeCee]

Not exactly sure what it proves. If the CAV is first in series, then I would hope it would capture more.
Or is your point that it lets something though?

Me: ditch the Nissan filter and change the CAV more regularly - they're cheap enough to do it every 5000 and still be in front.

[macca]

Not exactly sure what it proves. If the CAV is first in series, then I would hope it would capture more.
Or is your point that it lets something though?

Me: ditch the Nissan filter and change the CAV more regularly - they're cheap enough to do it every 5000 and still be in front.

Not sure if it proves anything.
And I have no point, only put the thread for discussion.
My observations are;
The CAV has a lot of crud in it, did it come from the fuel or my fuel tanks?
The CAV filter caught a lot of the rubbish, the Nissan looked to be fairly clean therefor did the CAV do a good job? or not?
Do you think the Nissan filter was a good backup?
Did I leave it too long between filter changes?
Do I replace the CAV more frequently?
If there was only the Nissan filter would it have let an amount of fine contaminants through to the pump / injectors?
What would have happened if they were the other way round?

Lots of questions, and hope some answers here will be of value to myself and others.

CAV cost about $7.00 Nissan $50.00 maybe change the CAV at each oil change and leave the genuine longer, a good point.
I will still leave the Nissan in circuit as it has the water alarm, my CAV is a cheapy without the alarm.
Cheers Macca

[nissannewby]

I would leave both filters fitted. I would just change the nissan filter every second service and the cav at every service. Could be from the tank could be a bad batch of fuel could be a number of things. Keep the 2 filters and you shouldnt have to worry about it getting much further than the second filter.

[macca]

I think you are on the right track there nissannewby, think this will be added to the maintenance schedule.

Was thinking 10k for the CAV and 20k for the Nissan.

Interested to hear what others do.

Cheers Macca

[nissannewby]

I would go 5 and 10. The biggest killer of injector pumps is contaminents. Being a diesel fitter myself I change all filters every 5k they are cheap both my 4.2's get done every 5 and both still on standard pumps.

[janderson]

If it works for you, keep doing it.

[bushytas]

WOW i asked this question in another post this is amazing and what i thought would be the case.

you might find the black sludge is a diesel bug it might be worth treating your tank to a fuel additive

I hear a brand called fuel keen is good but i have never used it I have used chemtech diesel power you can buy it from any repco store at around $15 a bottle 250ml

Hope that helps you a bit

Cheers
Brendon

[JoeG]

I installed a CAV filter/separator to my hilux in 1994, after a bad batch of fuel blocked the fuel pick up in the tank at 20,000km (i removed the in tank sock as it would not pass the black gunk)
the vehicle has now done over 300,000km, I changed the OEM filter at 200,000km as it was starting to rust on the outside, (I live on a dairy farm and the vehicle is always mucky from the cows droppings)
have always cleaned out the CAV every 5,000km since fitting it and always find a small amount of black sludge and some grit in the bowl, the black sludge and grit come from the local servo, if I see the tanker in the bay I try to wait a day before filling up to avoid as much as possible fuel from a stirred up tank
regards
Joe
PS have also fitted the CAV filter separator to my GUDX , Pajero and tractor for same reasons