Racor Fuel/Water separator - Half full and Air bubbles

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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

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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.

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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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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

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Yes, the hose is inside the tank Peter.

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Thank you for confirming, Ron.

Peter

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Thank you for confirming Ron!

Peter

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Peter, I went through many of the steps you have on our 1987 30U several years ago. We also had a 200 series Racor primary fuel filter. After much fiddling with hoses, fittings and filters I ordered a rebuild kit for the Racor. As I remember, replacement filters for the Racor included a large o-ring for the top of the filter assembly and and a small o-ring for the bottom drain fitting. The rebuild kit contained several other internal o-rings. Installing the kit parts fixed my problem. I have since replaced the 200 Racor with one of the newer spin-on filter units. You may want to consider that. Filter changes are easier with the spin-on type filters.

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Peter, a few years ago we had air ingress into our fuel supply and accumulating at the Racor. It took a couple of years for us to resolve the issue. The shut-off valve at the top of the tank was leaking air. We replaced the valve and have not had any trouble since—long shot maybe, but if you haven’t already done so, it may be worth considering.

…Ed
SaSeaCat 30Ultra, 322
Sarnia Ontario