Quote:
Originally Posted by funola
It is hard to determine where the leak is that causes a drain back. It could be from anywhere in the fuel system, above or below the level of where you see the drain back. Think of it this way, when fuel leaks out, no matter how small, it is displaced by air, which slowly works it's way to the highest point in the system. Your best bet is to fix any visible leaks first, one by one, till they no longer weeps, and see if that cures the drain back. If the air bubble/ drain back is still there, keep looking. A diesel fuel system should be totally dry, you should not see or smell any diesel.
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My delivery valves were leaking and I replaced the "O" rings today and that fixed that problem. I noticed that the fuel only drains back about an inch now in the clear line from the pre filter to the heat exchanger where before it almost drained back completely.
I'm tempted to squirt soapy water on every fitting and look for bubbles but I'm sure if it were to get sucked into a fitting that would be bad!
With all new clear lines it is much easier to see the fuel in the lines and I still see bubbles in the two lines on the lift pump. you can see it pulse with every stroke of the pump but it is much less than it was in the beginning.
This has really turned into a very frustrating project, I replaced both rubber hoses (feed and return) and hose clamps and all clear lines including every "O" ring (total of 18) and a new fuel pre heater that was cracked and leaking fuel.