Question about fuel tanks and diesel return line

[Photo Chief]

On an earlier post I told my sad story of diesel fuel and water contamination that I was having with the BMW D12 in my Bristol 27. Since I only planned to do mostly day sailing near the Norfolk area I decided to eliminate the internal tank and run on a small portable fuel tank much like the outboard powered cape dorys.

Today I returned to the boat to replace some brightwork that I had refinished. I warmed the engine up using the aforementioned portable tank but noticed that in about 15 minutes of running time the engine had "used" about three gallons of diesel fuel. I did not believe that it could be in the engine but I checked the oil level as a precaution. The level was normal so I sat to ponder the situation. Soon the lightbulb went on. The fuel return line to the main tank must be the culprit.

So the question is this. I am pretty familiar with gasoline engines but I am new to the diesel. I plan to pull and plug the return line. I cannot see how doing this will cause any other related problems but...Will this cause any other unforeseen problems? The PO told me he had paid to get the tanks cleaned but the problem came back. I plan to clean out the internal tanks but do not want to use them to avoid any repetition of the water condensation and biological activity happy times. What do you all think of my plan?

[Ron Turner]

Chief,

You can't plug the return line. A powerful fuel injection pump pressurizes the fuel lines going to the injectors. What fuel is not injected returns to the tank. Plug the line and you overpressurize other things.
I have been around several engines with the fuel return going somewhere other than the fueltank but still to somewhere. They have not returned "gallons " of fuel, maybe ounces.
I have used a portable tank on deliveries but I let the return fuel go to the tank or to some other secured container.

[Photo Chief]

Ron,

Thanks for your input with the return line. I thought it would be a good idea to ask before chopping off the limb behind me so to speak.

But the question remains. Where did the 3 gallons of fuel go? The fuel tank line passes through a hand primer bulb on its way to the fuel filter/separator. There is not fuel leak that I can detect. I connected the tank to the filter last week, ran engine a total of 15 minutes. Today the tank is empty.???

I will now purchase some more fuel line and run the return line to another small tank to test the amount of fuel that is returned through this line.

Puzzled in Norfolk.

[fenixrises]

Hi Rich,

Typically a diesel engine has a return for the diesel fuel. Your engine is probably still returning fuel to the old tank.

In addition to bleeding off the high pressures created by the injector pump the excess fuel flow often serves the additional purposes of lubricating and cooling the fuel injection pump. For these reasons it is vital to retain the fuel return feature of the fuel system.

Depending on the design of the pump and engineering of the engine the injector pump may circulate a great deal of fuel - far more than than the engine would ever use for combustion, for the above listed reasons.

Happy sails to you,
Fred B.

[Photo Chief]

Greetings again,

Today as I walked the pier to my Bristol 27 light snow was blowing sideways and I thought of you CDers up north. I went to the boat today to finally finished the installation of my portable diesel tank. I had to removed the fuel level gage assembly from the portable and use the hole to installed a return line from the engine. I ran the engine for about fifteen minutes without a problem. Hooray.

Now for a sail question. The mainsail on my boat does not appear to have any way to be reefed. No holes in the sail and no blocks etc on the boom. OK, I am a newbie and would not intentionally attempt to sail in heavy winds, yet as it stands now I am limited to under about 15-20 knots. As soon as I get some sailing hours under my belt I will want to try some over 20 knots. I was wondering about the sail reefing. Do I need to get someone to install reef points? Or is my newbyism missing something.

Thanks to Ron and Fred for info about the diesel return line.

[Neil Gordon]

The mainsail on my boat does not appear to have any way to be reefed. No holes in the sail and no blocks etc on the boom.

Chief,

There are four possibilities... in mast furling (not likely), a roller furling boom (could be, I suppose), grommets for a reef tack and clew but no reef points (not the usual, but a way to save some sailmaking $$$) or there is no way to reef the main.

Is there a former owner you can ask?

You can live without reefing hardware; which just makes it easier and quicker to tie in a reef. Same with reef points; they're only for tidying up the sail.

See your sailmaker if there is, in fact, no way to reef the main. It's not major surgery to modify the sail. Ponder whether the sail is old and it's worth it, though vs. a new sail (with two sets of reef points).

There's a safety factor in being able to reef. You can pick the weather you go out in. Not so for the weather that brings you back.

[Ron Turner]

Rich,

Back to the 3 gals of fuel used.
You may have siphoned it back to the old tank depending on how high the portable was in relation to the old. It should take an odd set of circumstances to do that BUT stranger things have happened on boats.