GMC Repair: diesel truck, fuel level sender, fuel leaks

Question
I have previously asked this question. Please forward to a diesel tech. I have 2003 2500HD 4x4 with 6.6 Duramax engine that I can not keep running unless I continuously keep pump primer pump on top of fuel filter. Previously I would prime filter and get it started and it would run all day, then one day it wouldn't stay running unless I keep pumping primer pump. Please help, no one in town seems to know what is wrong, and it's over 100 miles to the nearest dealership.

Answer
Hi
Having 8 years experience with the Duramax I can almost guarantee your problem is a leak. There are 3 distinct fuel zones on a Duramax. From the tank to the injection pump (including the filter) is under vacuum. (Called low pressure) The pump is fed by this fuel, and then increases the pressure to up to 22,000psi (high side pressure), which feeds the injectors. The fuel not used in combustion is returned to the tank through the return side of the fuel system. If there is either a fuel leak OR a vacuum leak, it will cause a problem VERY similar to what your describing. There may not be any VISIBLE fuel leak, I have had numerous where there was no visible fuel leak. FIRST check the entire fuel line system from tank to underhood for ANY visible fuel leaks. If you have any, repair them first and recheck. The common places I have experienced leaks are at the plastic fuel line under truck on top of tank where the line connects to the steel line that goes up to the engine compartment. The filter gasket. Either of the 2 "banjo" fitting seals on the FICM (the control module located next to the filter). The rubber fuel line to the steel line also at the filter. Also check the small plastic fuel pressure port cap, located on the drivers front next to FICM. Make sure it has a small rubber seal on the inside and make sure there is no fuel in that area. There is also a small possibility it COULD be a check valve inside the fuel tank located on the fuel tank module (The module is what the fuel level sender is mounted on). And the Filter housing itself has a check valve so it could also be at fault. Also check the fuel cooler, located under the truck by the tank (looks like a mini radiator) for any leaks. You may also while under there clean out the fins with compressed air.  For ease I would recommend either lowering the tank or removing the bed to gain access to the top of the tank so you can really see top of tank good.
These are just suggestions.
Good Luck
Pawl