The little diesel pump for the Racor filters - 2

Later August - Paradise Village Marina in Banderas Bay Mexico

 This piece of 3\4 inch marine plywood was left over from another project. We cut it to fit in the engine room where we will attach a diesel pump for back filling the Racor filters after we drain the bowel of dirt and water. Racor suggests doing this every 10 hours of engine run time. Back filling the fitter with a can of diesel is a pain plus we need to store the can. We painted the wood with silver engine paint we got at Autozone along with the pump.

The spot for the pump.

The Marine 3/4 plywood we made up for mounting the pump.

Still a work in progress.

The blue seas switch we will use to turn on and off the pump when needed. We made the switch plate out of 1\4 inch marine plywood. It was left over from a job on the boat.


  1. I can't understand the reason for a back filling operation every 10 hours of operation, since the filters don't need to be changed nearly that often. That process could be after 1 or 2 days of engine operation. Are you sure they didn't mean every 100 hours?

  2. That was after 10 hours of engine run time you should drain the filteroh water, crud etc. That requires filling the filters back up with diesel fuel so not to get air in the system as far as I know. I can re-read the manuel.
    Hope this helps,

  3. On our Pathfinder we have one stock, spin on fuel/water separator filter, and one Racor using a 30 micron filter after the stock filter. The few times I've checked the stock filter for water in the fuel (I've never found any to date), I haven't topped off the filter before starting the engine, and there wasn't a problem. If I was going to replace the stock filter with a new one, I would top it off with fuel before putting it on because otherwise it would be dry to start. I just changed the Racor filter without topping off the fuel (The fuel level was only about 1/2 to 3/4" lower after the change), and no problems running the engine. When I change engine oil filters I top them off before putting them off, otherwise they would be dry and might cause a problem. On cars when either fuel or oil filters are changed, no one tops them off before running the engine, but I think that is because fuel filters on cars are much smaller, and oil filters on cars work at lower pressure levels.

    I'm not trying to talk you out of what you're doing, I just haven't experience a problem changing a Racor filter without topping it off. If I lowered the fuel level in the Racor down much farther than I do, then I would top it off. Maybe different engines have different requirements in this regard.

  4. Well I think you have been lucky. On the diesel side of filters they should always be back filled.
    You can check this YouTube video out for the Racor filters.
    I also sent off an email to Phill Jones "The Marine Man' who installed our Beta 38hp in our boat asking about this question.

  5. After looking at the Racor video, and re-reading my Pathfinder manual, I know why the Racor filter needs to be topped off.

    On a Racor the fuel enters and exits the Racor body at about the mid-point of the filter body, and if the fuel is not topped off above the enter/exit ports this creates an air pocket above. The part of the filter above the ports stays dry because of the air pocket, and only the part of the filter at the level of the ports and below will filter fuel...essentially making the filter surface smaller.

    The fuel enter/exit ports on the Pathfinder stock spin on filter, are on the very top of the filter body so no air pocket can exist. The Pathfinder manual says that after changing a filter or bleeding a filter, open the fuel valve from the fuel tank to gravity fill the fuel filter, and then run the engine.

    Good to know how different fuel filter setups work huh. Now I need to check my Racor next time I'm at the boat to make sure it's topped off, so the whole filter is filtering.