Fuel tank pick up air leak

[Rusty68801]

I have a 1984 Hunter 31 I have been getting air in my fuel system. I started with new fuel lines then a new fuel pump. Checked filters installed a new fuel water separator filter and gasket. A mate then told me to check the fuel pick up. I removed it from the tank and it is an aluminum street elbow with an integrated hose barb under the threads. It has a hard plastic tube on it that appears to have been heated to originally install. Of course it is hard and brittle, it swivels around the barb very easily and could very well be where the little bit of air is coming from. Now the question I am looking at putting a 20" long Tygon hose on the barb, Yes I know I will have to fashion a clamp over that connection because over time the tube will swell and leak air once again. Then installing a brass fitting in the inlet end of the tube with a brass screen fashioned over the inlet side of the fitting. So the pick up tube can slide around the bottom of the tank. That being considered can anyone see why I shouldn't do this?

 

[Bill Roosa]

The fuel tank pickup should be "underwater" all the time except for the last few gallons. Can't get an air leak unless that part of the pickup is exposed to air!
Air leaks are always found in the suction side of the system. a leak in the pressure side will leak fuel out. Since you have replaced the filters etc are you sure you got all the air out after replacing them?
I don't understand what you are explaining with the Tygon hose stuff. Try starting at the tank wall fitting and walking us through it to the pickup end.

 

[kloudie1]

Rusty, it might be best to replace the hard plastic tube with a copper or stainless one. Make it so that it clears the bottom by a quarter inch or so as did the original. You can solder it into the tank fitting (as long as there is a good mechanical connection) so that it doesn't leak air there at the top. I would not put a moving pickup inside the tank (like my weed eater has to allow it to feed fuel no matter the position). The little screen on the tip of the pickup is not necessary and most folks remove it, preferring to have the debris caught by the primary filter rather than plugging the tip inside the tank where is is very difficult to clean.

 

[Rusty68801]

Bill, The fitting at the top of the tank is a Street elbow with a hose barb sticking down in the tank through the threaded part of the tank. it is made all one piece. Tygon tubing is a fuel line that is very flexible and my tank is 11 inches deep, 16 inches wide, and 24 inches long. the hypotenuse of the 11 X 16 face of the tank is a little longer than 19 inches and the hypotenuse of the 11 X 24 face of the tank is a little longer than 26 inches. that is how I decided upon about 24 inches long. I will put a heavy enough weight on the end of the very flexible hose so when the boat rolls from side to side the weight will travel to the low side of the tank. A 24 inch hose will allow the weight to travel from one side of the tank all the way to the other side with out hitting the back of the tank. The current pick up is placed in the front port side of the tank and extends to with in a 1/4 of an inch of the bottom of the tank. So when I am low on fuel and she rolls to the starboard side while I am motor sailing I will pick up air. My though is with a "Clunk" and a flexible tube in the tank it will always be under fuel. My question is can anyone see why that would not be a good idea???

 

[Chris Patterson]

Rusty, I have thought this over for two days, and have given it some consideration in the past. I 'worried' the problem of the weighted line settling into a groove, and am still not convinced that it would not. In fact, it probably will to some extent. However, it will solve the problem of fuel sloshing above the pickup. Myself, in your shoes right now; I would have to try it.

 

[Rusty68801]

Thank You Chris

 

[kloudie1]

Couple of things to ponder, Rusty.. There are several different "Tygon" formulations.. some aren't compatible with diesel. I think F-4040-A is the correct one. The chemicals in diesel biocide and anti-oxidant may even attack the best Tygon. When the flex tube breaks off at the flex point, the top, there will be no pickup.. Not saying it is a bad idea, just saying I wouldn't do that..

 

[Bill Roosa]

Kinda poor tank design IMHO. tanks should have a Vee bottom to prevent this sort of thing

 

[Rusty68801]

Thank you ALL for your thoughts. Very helpful, I will let you know how it turns out.