Fuel leak when full down to 7/8 full only HELP!!!

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rockytopcummins

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I have never been so aggrivated by a problem on my truck because I can't figure this out to save my life. This thing will pour fuel on the hog head while driving and then slow to a drip at idle and no leak when the engine is off. Also, it only does this between a full tank and 7/8. Once I run about an eighth of a tank it it quits. Plunger on top of the pump, fuel lines, supply line and return line are all dry. Nobody I know has a clue, I'm hoping someone here does. Garmon's is about three hours from me and that's about the closest reputable shop to me. I really hate to drive that far but it's about to come to that if I don't get this thing figured out.
 
Make sure the vent line that runs up to the filler neck tube is intact and connected.
 
I don't know anything about your specific setup but it sounds like the water in fuel drain is getting tripped somehow. My 99 used to trip on me when it was real cold sometimes, it was real wonky like that. I ended up eliminating that filter with an air separator setup. Hope it gets you closer. 2¢
 
He's leaking fuel over the front Axel no part of the tank is near the front Axel or over it for that matter.
 
Mountainman234 said:
I don't know anything about your specific setup but it sounds like the water in fuel drain is getting tripped somehow. My 99 used to trip on me when it was real cold sometimes, it was real wonky like that. I ended up eliminating that filter with an air separator setup. Hope it gets you closer. 2¢
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I have an Air Dog so I don't think that would be an issue either.
 
How close have you looked at the return lines? As the fuel level in the tank gets higher there COULD be more restriction on return flow, as fuel level drops restriction goes away and therefore so does the leak. Could be either fitting at the rear of the engine, fuel runs onto the block then forward on the oilpan...
 
How is your fuel return from your p-pump run? The injector return comes out of the back of the head (at the fire wall) comes around the drivers side and has to connect to the return from pump one of those lines/fittings is leaking,
I would bet money maybe even cracked. Have a buddy put air pressure in the fuel tank NOT very much like 3psi and look for leaks if its leaking you will find it good luck
 
I have seen someone install an airdog 150 and not block off the stock feedline, just remove it from the stock lift pump and leave it hang. This caused the exact problem you are describing. The air pressure should help you find your problem.
 
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