Bmc 1.8 bleed issue

[Tony Brooks]

39 minutes ago, rusty69 said:

Our boat has only ever had the one filter connected after the lift pump.I have always known this isn't really ideal, so a few weeks ago fitted one of these, before the lift pump (thanks @gazza):-

 

 

 

https://www.ssldieselparts.co.uk/aluminium-sedimenter-double-dfas1-p-722.html

 

 

 

These two items are available as separate units and with this sort of combined unit it is very important to have the fuel flowing through it in the correct direction. In this case right to left.

 

The right hand unit is a sedimentor with just an inverted cone inside it so as long as its not full of water & muck it is very hard to block. Basically it centrifuges about 80% of the water and any large chunks of muck out of the fuel. It will leave about 20% of any water in the fuel in fine droplets. This is where the second unit comes in.

 

The left hand unit is an agglomerator, as is your and every other engine filter. The centre section is a very common filter. Those droplets of water get trapped on the surface of the filter medium until they agglomerate together into larger droplets. At that point the pressure inside the water droplet (fuel pressure x surface area) is sufficient to force it through the filter where being much larger and heavier it drops to the bottom of the bowl.

 

Although I have both between tank and engine if money is an issue I would fit just a sedimentor and leave the engine filter to do the agglomerating.

 

 

 

[Tony Brooks]

PS - Well done SamT and thanks for the feedback.

[Bee]

My system can be tricky to bleed, I always have a couple of litres of fuel in a bottle before I start and fill the filters before I spin them on. Saves a lot of effort and sometimes you really are not sure if anything is happening when pumping by hand.

[Sam T]

All makes a lot of sense. Thank you.

[Tony Brooks]

2 hours ago, Bee said:

My system can be tricky to bleed, I always have a couple of litres of fuel in a bottle before I start and fill the filters before I spin them on. Saves a lot of effort and sometimes you really are not sure if anything is happening when pumping by hand.

Not on a standard BMC you can't. The filter assemby comes in three parts with O rings between each part    and they are not fuel tight until they are assembled and the centre bolt tightened.

 

Sam T  would just spill most of the diesel out all over the engine and starter.

[rusty69]

5 hours ago, Tony Brooks said:

 

These two items are available as separate units and with this sort of combined unit it is very important to have the fuel flowing through it in the correct direction. In this case right to left.

 

The right hand unit is a sedimentor with just an inverted cone inside it so as long as its not full of water & muck it is very hard to block. Basically it centrifuges about 80% of the water and any large chunks of muck out of the fuel. It will leave about 20% of any water in the fuel in fine droplets. This is where the second unit comes in.

 

The left hand unit is an agglomerator, as is your and every other engine filter. The centre section is a very common filter. Those droplets of water get trapped on the surface of the filter medium until they agglomerate together into larger droplets. At that point the pressure inside the water droplet (fuel pressure x surface area) is sufficient to force it through the filter where being much larger and heavier it drops to the bottom of the bowl.

 

Although I have both between tank and engine if money is an issue I would fit just a sedimentor and leave the engine filter to do the agglomerating.

 

 

 

You have me thinking now Tony. I am sure the one I have has two inputs and two outputs. 1 in on the left, 2 out on the left. 3 in on the right and 4 out on the right. I have used an in and an out and blanked off the other two. 

 

I will have to look in the morning. 

[Tony Brooks]

7 hours ago, rusty69 said:

You have me thinking now Tony. I am sure the one I have has two inputs and two outputs. 1 in on the left, 2 out on the left. 3 in on the right and 4 out on the right. I have used an in and an out and blanked off the other two. 

 

I will have to look in the morning. 

That is the way the filter heads are made but when the pair are on a common top casting for optimum efficiency you need to get the fuel into the sedimentor first so that can remove the larger pieces of muck and water so they do not block the true filter. As I don't know where the galleries go inside the casting I would just make sure the pipe from the tank goes to the in arrow port on the sedimentor. If the galleries are cross connected so both inlets go to the sedimentor then fine but they may not be because on some installations a return from the injector pump would be fitted into the agglomerator (filter) side inlet port.

[rusty69]

21 minutes ago, Tony Brooks said:

That is the way the filter heads are made but when the pair are on a common top casting for optimum efficiency you need to get the fuel into the sedimentor first so that can remove the larger pieces of muck and water so they do not block the true filter. As I don't know where the galleries go inside the casting I would just make sure the pipe from the tank goes to the in arrow port on the sedimentor. If the galleries are cross connected so both inlets go to the sedimentor then fine but they may not be because on some installations a return from the injector pump would be fitted into the agglomerator (filter) side inlet port.

Thanks Tony. Just looked. It is actually in 1, out 2 on left and in 4,out 3 on right.

 

So until I can prove otherwise,if I understand correctly you reckon I should connect the output from the tank to in 4 on the right and out 2 on the left to the lift pump. 

[Tony Brooks]

3 minutes ago, rusty69 said:

Thanks Tony. Just looked. It is actually in 1, out 2 on left and in 4,out 3 on right.

 

So until I can prove otherwise,if I understand correctly you reckon I should connect the output from the tank to in 4 on the right and out 2 on the left to the lift pump. 

Sounds correct.