A question for Racor 500FG experts

[bluedragon]

My recently installed filter is above the fuel tank and lift pump. It has a shut-off valve on the downstream side, but not to the tank itself. What will happen when I open the top to change the filter. Will it drain down into the tank and leave both filter and piping empty, or is the design such as to prevent this? If it does drain down, then filling the unit with diesel from the top after a filter change will not work and I'll need to install a check valve or shut-off for the inlet, or suck it through conventionally via the lift pump (which defeats the object of this design does it not).

An associated question: with the present set-up what will happen when I open the bowl cock to drain-off water? Will this work properly? If water comes out, where does the fuel come from to replace it (or does air get in). The more I try to envisage all this, the more confused it becomes! I could of course just try it and see, but don't want to mess around before setting off this weekend. Hopefully nothing will need to be done until the winter anyway, but just in case it would be good to know.

Thanks.

 

[vyv_cox]

I can't claim to be an expert in this type of filter, but other than its internal turbine features it doesn't appear to be unusual in its general design. Mounting it above the level of the tank would seem to be a long way from ideal, for the reasons you have identified. Opening it, either to change the element or to drain off water, will allow air into it and allow fuel to run back into the tank. Fitting a check valve or a stop-cock in the inlet line would allow you to partially fill it with fuel, but you then cannot bleed it, so all air will have to be bled right through to the next available point using the lift pump. You will not be able to drain water from the bowl by closing an inlet valve.

 

[rotrax]

My recently installed filter is above the fuel tank and lift pump. It has a shut-off valve on the downstream side, but not to the tank itself. What will happen when I open the top to change the filter. Will it drain down into the tank and leave both filter and piping empty, or is the design such as to prevent this? If it does drain down, then filling the unit with diesel from the top after a filter change will not work and I'll need to install a check valve or shut-off for the inlet, or suck it through conventionally via the lift pump (which defeats the object of this design does it not).

An associated question: with the present set-up what will happen when I open the bowl cock to drain-off water? Will this work properly? If water comes out, where does the fuel come from to replace it (or does air get in). The more I try to envisage all this, the more confused it becomes! I could of course just try it and see, but don't want to mess around before setting off this weekend. Hopefully nothing will need to be done until the winter anyway, but just in case it would be good to know.

Thanks.

Hi, our Racor is mounted like yours. If you are only draining a small amount of water or sediment it seems to drain to half empty OK. To get more out loosen the top to allow air in to clear the vacuum produced by draining. If you then remove the top and the filter element and top off with clean fuel,then replace the element and top this will minimise bleeding. We are fortunate-the maker of our boat fitted an electric pump for the purpose of bleeding so i'ts a doddle!

 

[bluedragon]

I wondered about putting a squeeze bulb on the input side to act as check valve and means of filling the unit? Does yours have any shut-off or valve to prevent drain-back into the tank, or does this not happen anyway?

PS - from a diagram I've seen, there is a ball in the filter which seems to act in some way as a one-way valve, but it's not clear whether it's in the input or output.

 

[vyv_cox]

I wondered about putting a squeeze bulb on the input side to act as check valve and means of filling the unit? Does yours have any shut-off or valve to prevent drain-back into the tank, or does this not happen anyway?

PS - from a diagram I've seen, there is a ball in the filter which seems to act in some way as a one-way valve, but it's not clear whether it's in the input or output.

I looked at a few diagrams yesterday and didn't see any check valves. If I missed it, sorry. The squeeze bulb would be a good idea, I seem to remember that Skipper Stu has advocated this method from his experience.

 

[bluedragon]

I've looked in various places (inc. a call to Parker/Racor UK) to find out what this ball actually does. I've got various answers that don't make it any clearer! I've got a non-return valve coming in the mail should I need to fit it in the feed line, and depending how I get on with changing the filters / re-filling from the top, may well fit a bulb. Supposedly, done correctly, there's often no need to bleed the system after a filter change, which is very useful if it has to be done in a hurry or at sea. I need to play around with it when we're NOT setting off somewhere.

 

[The engineer]

If I remember correctly this filter has a silver ball that floats in water and sinks in diesel. If the water level in the bowl rises it serves to stop it going to the engine by blocking the hole.