Racor Fuel/Water separator - Half full and Air bubbles

[Peter Grabow]

Hi All,

My W27A engine runs well, but a couple of seasons ago I noticed the Racor fuel/water separator was only half full, and it has been this way but no engine issues (though I do feel the engine isn't putting out as much power ie the boat doesn't seem to move as fast under power, though that could be from a number of other things - dirty bottom (just cleaned) prop pitch, etc.

Within the last couple of days I decided to check the Racor again as we are sailing to Maine over the next 4-5 weeks... when I turned the ignition key to let the fuel prime, I noticed air bubbles forming at the top of the fuel in the filter (again, only about half way up).

I decided time to change the filter and o-rings. so I did that this morning and when the filter self primed it filled all the way (don't get too excited, there's more...). I let it sit for a while to allow the new filter to absorb as much fuel as possible. After a while it was still full... so I motored over to the fuel dock to top off the tank for our upcoming departure, and when I got back to the dock, expecting to see the Racor full of fuel and the problem solved - it wasn't! 

The Racor was half full again and when I look at it with the engine off but key turned on so it will prime - air bubbles again.

The fuel lines attached to the Racor all look good, as do the rest of the fuel lines. There is no evidence of a fuel leak and no fuel smell...

But apparently air is getting in from somewhere...

Suggestions????

Thank you,

Peter Grabow

S/V CAKE WALK III

1987 30U 430

Stamford, CT

[JohnS]

Check the vent line. You are creating suction here. Presumably using the old clear-class-bowl racor filter?

Also, the clear "glass" might be cracking, letting in a tiny bit of air under vacuum. Ours did, and I obtained a new glass bowl. The air bubble stream was hard to see, but when lit properly, there it was, a tiny stream of air bubbles

Note that, if you sell your boat, the surveyor might require changing fuel filter for a modern one.

John Stewart

Boatless in Ottawa.

[Ron Schryver]

Hi Peter, one obscure source of air is from the pickup tube in the diesel tank itself. It happened to our 1987 30U and a very clever mechanic discovered it. There's a hose on the end of the brass fitting that goes into the diesel tank. This hose is friction fit and glued to the brass fitting. Over the years of fuel sloshing back and forth this hose worked slightly loose. When the diesel tank was filled to the top - no problem. As soon as the diesel level dropped below the connection point of the hose to the fitting air would get drawn in along with the fuel. We simply cut off an inch of the hose and reinstalled it and it has been fine ever since.

Hope this helps......Ron

Ron & Diane Schryver

"Alpha Waves" 1987 NS30U #393

Georgian Bay Midland ON

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[Peter Grabow]

Thank you John and Ron for your input/suggestions.

When reviewing the Racor 200FG parts list and trouble shooting suggestions, I noticed that there is an O-ring for the bowl as well as the two O-rings that come with the filter replacement.

I will check to see if this O-Ring may be the source of the air leak and hopefully have/or can find, the proper size O-ring to replace...

John - I will check the vent line. The bubbles are fairly easy to see so I suspect that more than a micro-crack in the bowl is the source, but I will double check the bowl as well.

Ron - the hose which you mention... this is inside the tank, or on the exterior of the tank at the pickup fitting.  The tank is full and air bubbles are still seen... I will check the exterior connection to ensure that this fitting is secure.

Best regards,

Peter

S/V CAKE WALK III

1987 30U 430
Stamford, CT

[Ron Schryver]

Yes, the hose is inside the tank Peter.

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[Peter Grabow]

Thank you for confirming  Ron!

Peter