Diesel in bilge

[Akapeterc]

I have a problem everytime I fill my diesel tank to the top I get diesel fuel in my bilge. I cannot find any diesel leaking around the filler hose at the top or where it goes into the tank. Once the tank goes down I don't have a problem. Any suggestions where I should look. Very hard to follow the line from the tank to Filler cap. There is definitely no oily feeling on the pipe at both ends. My boat is a 2003 Hunter 44 DS. Is no sign of any fuel leakage around the motor. I can't even see how it gets into the bilge. Any suggestions where to look would be very helpful. Thanks

 

[KD3PC]

first, never fill a fuel tank (gas or diesel) to the top....the fuel needs room to expand....and when it expands, it has to go somewhere.

You will need to find the overflow for the fill tube...they usually dump overflow, overboard...thus you see products/funnels/rags placed under or in the overflow. Similarly the "vent" tube, if the overflow does not act as one.

Perhaps your overflow/vent hose is broken or drains to the bilge, although being a newer boat that seem unlikely. I sooner think a cracked hose or loose clamp, somewhere along the filler hose/vent/overflow hose.

Usually diesel will leave a stain/mark on clean fiberglass where it "runs" down. You can try the spread some talc or chalk line chalk along suspect areas (works for water leaks, too) to make sure

 

[kloudie1]

I just had a similar problem and it was a cracked fuel return hose from the injectors. Usually a 1/4" hose. As KD3PC says, the other prime suspect here is the fuel vent line. a 5/8" hose from the top of the tank to the tank vent on the outside of the boat. Check the hose clamps, but it may be that either the return or the vent has a crack in it.

 

[Don12364]

I would wager it is from the air vent pipe. On my H376 this pipe exits the top of the tank, runs alongside the filler pipe and then overboard. Returning from holiday in Holland one day I filled up in my last port of call and it was a hard beat all the way back along the English Channel to the Solent. When we arrived we were noticeably low on fuel and I puzzled over possible reasons.
There were no leaks and eventually we found that the answer was because the overflow pipe did not rise high enough above the top of the tank. When heeled on port tack the inboard end of the tank was raised high enough to allow diesel to dribble out into the sea.
I had been polluting the whole of the first 50 odd miles of English Channel. All it needed was six feet of flexible pipe on the overflow and clipped up under the deckhead until eventually exiting overboard. No amount of heeling will cause the diesel to overflow now.
See attached drawing from 2006.

 

[splax]

I think that I have another vent hose on my tank top valve that acted as an overflow before my outboard overflow started to work the first time I filled up. Search the forums for "diesel fill bilge" and you will find material to help you solve your issue.

 

[Mike H.]

I had a similar problem on my 94 vision 36.

I searched for months. It turned out to be crushed and cracked fill hose between the hull and the fill opening on the tank.

When the boat was built the workers installed the tank, fill and vent hoses then they glassed on the cockpit locker floor on top of the tank and hose. They did not allow enough clearance between the bottom of the cockpit locker floor and the top of the tank. They crushed the hose and that is where the crack occured in the hose about 14 years later.

I had to cut away a piece of the cockpit locker floor to remove the leaky hose.

Good luck!