Gas Line

[alldodge]

I think were going down a different rabbit hole

 

[bobdec]

I agree w/unclewillie post #16 . OP has 2 (two) engines sucking the 2 separators dry , that were previously filled and primed with fuel. Something has to displace the fuel leaving those filters or they would not be empty. Either both have an input air leak or the common feed line to both filters has a leak. Also in post#16 we did not get an answer to the missing plug in the filter input pic in post #8

 

[alldodge]

Post 8 is just a pic, yes the plug is missing, but its just a pic with arrows pointing out the two ports which can be used for incoming fuel.

 

[carrier82]

I disagree with bobdec and claim that it may also be possible that the fuel hoses are full of air between tank and filter which the fuel pump is unable to solve. Although an air leak may also be possible.

 

[UncleWillie]

An air leak is the most likely cause. <----<<<

Examples of Positive Displacement Pumps are Piston, Gear and Diaphragm Pumps. Like most Fuel pumps are.
Examples of Non Displacement Pumps are Centrifugal/Inertial Pumps. Like your bilge pump and the fuel pump in your auto that is in the fuel tank. They can push, but can not pull.

The fuel pump in the boat has significant suction capacity.
They need to have enough pumping power to open the anti-siphon valve on the tank and then pull the fuel up to the engine.
The anti-siphon valve is required to remain closed until more than 20-24 inches of water column pressure is present. That is nearly 1 psi.
It is unlikely that any portion of the fuel system exists 4 feet above the tank, even if it did, that would only present <2 psi of counter pressure.

A diaphragm pump with only a 2:1 pump stroke will generate ~7psi of suction. It could pull fuel up 20 feet.
We are not really asking much of the pump.

 

[frantically relaxing]

Yes, an air leak IS the most likely cause, and almost a certainty. In this case the air leak is somewhere between the new filter and the tank. The reason it's a certainty is simple- the pumps are sucking the gas out of the filter(s). The only way this can happen is if air is getting in the line somewhere. Otherwise, there's only two other possible options: The pumps aren't pumping (they are) or the tank is empty (???) and the air is getting in THAT way. Working fuel pumps with no air leaks and fuel to suck up will suck fuel just fine, and move along any air bubbles that might be in the line.

But since fuel IS moving from the filter to the engine, but NOT from the tank to the filter, an air leak (or empty gas tank) is the only possible explanation...

 

[carrier82]

After rethinking this, air leak it must be. There is no way for the pump to empty the fuel filter without the fluid being replaced by fuel or air (it would create a vacuum behind the filter. It can only be air if the tank is empty or there is an air leak.

 

[HPLou]

Thank You all for the help. I have installed Plugs on the Inlest & Outlets that are not used. To seal them, I used Form A Gasket Aviation #3.
I have 2 separate Fuel Lines that comes out of 1 Fuel Tank (240gallons) and I have installed 1 Fuel/Water Separator Kit on each Line.
The Fuel Water separators are located near the Fuel Tank, approx in the middle Height of the Tank. I have not increased the lenght of the Fuel Lines.
Both Engines will stall after burning half or 2/3 of the fuel in the filter.
You must be right, there is no Fuel in the lines beetween the tank and the Fuel Water Separator.
I will have to tight the Collar on both Lines and see if there is Air Leaks.
I have no Fuel Leaks at all, so I think there must have no Air Leaks also!

It will rain all weekend, so I will spend time to work on my problem. I will be back soon with results
Thanks Again

 

[Grub54891]

How full are the tanks? If there is a pinhole in the pickup tube,it'll run till it gets below that level,then suck air.

 

[bobdec]

I apologize , in post #28 you just said "Both Engines will stall after burning half or 2/3 of the fuel in the filter. " I misread your original symptoms and thought the filters were sucked dry and incorrectly put that in my head. If 1/2 of the fuel is still in the filter then it sounds like an obstruction with, or feeding the filters. Or air leak has to be between filter and fuel pump. A mini-vac pump or vacuum gauge on the filter inlet would isolate problem. Or an outboard primer bulb (for testing only) on the filter outlet to engine with engine hose disconnected and emptying into a can or bottle (to collect fuel) would test the tank through filter operation in a heartbeat.. Then attach the fuel line to fuel pump and again squeeze bulb looking for a leak in line and fittings to pump. Then start engine and if bulb collapses it proves you have an obstruction, if bulb stays full then it's an air leak. Shot-gunning and guessing can get frustrating..

 

[HPLou]

For testing,
The Fuel Tank (240 gallon ) is at 50% Full And always was.
I have removed both Fuel/Water Separator Bracket Kit from both Fuel Lines use a brass male adaptor with collar to connect both ends of Fuel Lines (both Lines)
I have ran the engine for 5 minutes without the engine stalling. I went for a 15 minute ride, Engines are running perfectly.
This tells me that there is no Air Leaks or Fuel Leaks Beetween the tank & fuel pump on both Lines.
My problem has to be in the Fuel/Water Separator Kit that is not compatible. It is very strange that both kits acts the same way.

 

[UncleWillie]

...I have removed both Fuel/Water Separator Bracket Kit from both Fuel My problem has to be in the Fuel/Water Separator Kit that is not compatible. It is very strange that both kits acts the same way.

Now we have narrowed it down!
Whatever is wrong is wrong with both.
Do you have all the seals and gaskets in place?
The seals on the face of the filters will sometimes jump out of place.
It seems the manufacturers try to save a little cost by not glueing the gaskets in like they used to.
Also be sure you are using the correct Filters. Just because it will thread on doesn't mean it will seal.

There is an air leak in there somewhere. Plug three of the ports and blow air into the fourth to see where it comes out.