About this diesel pre-filter

[Cuan]

Thanks, it might be a better idea to install a glass bowl as well. there is a version that allows you to drain off water as per lw's response. Thanks

 

[jbweston]

I have at the back of my mind that in some circumstances glass bowls are not permitted. Possibly on inland waterways and on new builds under the RCD where the filter is in the engine compartment. I'm not sure about that and don't have time to look it up at the moment.

I know that Penguin came new with a metal bowl and I swapped it as I really want to know if the bowl is filling up with muck or water and with a metal bowl I'd never know unless I'd been disciplined enough to drain a little fuel off into a glass jar every time I did an engine check. Much easier just to take a quick look at a glass filter bowl.

 

[pvb]

I know that Penguin came new with a metal bowl and I swapped it as I really want to know if the bowl is filling up with muck or water and with a metal bowl I'd never know unless I'd been disciplined enough to drain a little fuel off into a glass jar every time I did an engine check. Much easier just to take a quick look at a glass filter bowl.

The glass bowl contains filtered fuel, so you won't see muck. There might be some water, but in my experience it's rare.

 

[lw395]

The glass bowl contains filtered fuel, so you won't see muck. There might be some water, but in my experience it's rare.

Long may it stay 'rare'.
An alternative to a glass bowl is to have a water sensor in the filter.
A lot of vehicles have this.
Usually in a plastic filter body...
If you are worried about the effects of an engine fire on your filter, then it's probably best to have it outside the engine compartment.
Lot to be said for that anyway, depending on the layout of the boat.

The much-maligned CAV filter scores because I can buy a filter element almost anywhere so cheaply, it can be changed at the slightest suspicion of trouble.

 

[Ruffles]

You could, with bottom cap on, but it would be messy.

I always do. It's above the tank so any spillage is used to stop the tank rusting!

But you can pre-fill it from the bleed screw on top of the casting if you have a steady hand and enough headroom.

 

[Graham376]

The much-maligned CAV filter scores because I can buy a filter element almost anywhere so cheaply, it can be changed at the slightest suspicion of trouble.

CAV filters are a nightmare to change at sea if the boat's rolling around (been there & done that) whereas a separate glass bowl sediment/water trap before a spin on filter is much faster and easier to change. These are fairy cheap and effective - https://www.ebay.co.uk/itm/Fordson-...919763?hash=item4b08b977d3:g:8YIAAOSwv8FZ3pNJ

 

[lw395]

I don't think those are nearly so effective as a CAV type when it comes to separating water droplets that are well mixed with diesel.
It might be interesting to try one on a polishing rig.

It takes quite a lot of water to fill a CAV.

 

[psousa]

Found it:
https://www.youtube.com/watch?v=VfoRgHsiUqU

you open this by unscrewing the top screw! That's what I was looking for.

 

[pvb]

you open this by unscrewing the top screw! That's what I was looking for.

I don't think you actually asked that question though!

 

[psousa]

yes. asked for a video where they explain how to change the filter here, so... how to open, change, reassemble and bleed it. That's what happen when you change a diesel filter/pre-filter. I think.

 

[De.windhoos]

when assembling the filter you need to be sure that the lower o-ring is set properly. This can be a pain in the ass.
when you can't bleed the system in like 5 minutes it's highly probable that the ring has moved when placing or tightening the bowl

 

[psousa]

Thank you for the advice.
I'm still postponing this maintenance, mainly because I'm afraid of a wrong bleeding and then, a major problem will come.
Can I use the small lever on the fuel feed pump? Even knowing the fuel feed pump is AFTER the CAV/pre-filter and I need to keep the bleeding nut open on the top of the CAV/pre-filter until I get diesel coming out? My first thought is that wouldn't work because can't create vacuum since I need to keep the CAV bleeding nut open.
Or should I keep the CAV air bleeding nut closed and bleed all the system until the regular diesel filter which is installed between the fuel feed pump and the injection pump?

 

[PaulRainbow]

Thank you for the advice.
I'm still postponing this maintenance, mainly because I'm afraid of a wrong bleeding and then, a major problem will come.
Can I use the small lever on the fuel feed pump? Even knowing the fuel feed pump is AFTER the CAV/pre-filter and I need to keep the bleeding nut open on the top of the CAV/pre-filter until I get diesel coming out? My first thought is that wouldn't work because can't create vacuum since I need to keep the CAV bleeding nut open.
Or should I keep the CAV air bleeding nut closed and bleed all the system until the regular diesel filter which is installed between the fuel feed pump and the injection pump?

You are correct that you need to keep the CAV bleed screw closed if you use the hand pump on the engine, otherwise it will just draw air in. There should be a 10mm bleed screw on the secondary filter, open this one turn and use the hand pump until no air comes out. Don't drank the engine too long if you have the sea cock open.

 

[psousa]

just to update: bleed using the secondary filter pump, with the CAV bleed screw closed, until the diesel shows up on the top of the secondary diesel filter cap. Not fast but not that slow. I was expecting more time pumping :-O
Did this long time ago and so far so good. No problems. I'll do it again soon since I used the engine a lot this season :-|