allright so i have a 3500 no duels 99 5 speed. no fuel gauge(i know guys).bone stock. i took off the chips(hyperteck,edge ez).problem still exist. i replaced my grid heater relays.that works fine.i have clean fillters and regularly do fuel water separator. i have a new stock lift pump.stock vp.and 244.000 miles. so when i point the nose down hill a little or a lot it fires right up,hot or cold(cold -10).when the nose is pointed up or on level ground it flat out gives me hell starting.regardless the fuel level in the tank. i can start it and shut it down and come back 2min latter and it has a hard time starting on level ground. point it down hill and come back 3 weeks latter.fires up no questions asked. it started to hesitate and took two cranks of the key then it would fire.now its blown a starter and takes 3-5 cranks on the key.the problem stated 5kmi after new lift pump.when its on the highway(no chips) it runs like a dream.no bog,no hesitation, from a start to 110mph its solid.just when i shut it off on level ground it hates to start.pointed down hill at all it fires up and runs great.no visable leak frome vp,lift or the fuel lines,or the T on the back of the block.the frame dosnt show any sign of fuel drips.i put card bord under it and no drip any where.nose up hill or down.fuel gauge goes on next week.i degreased the whole block lift pump vp,lines...its shiny like new.and still no leak can be found.my best gess and thats a GESS is a broken return line or loose fitting (T fitting on block).injector lines are tight fuel filter cup is tight with gasket and no thers not two gaskets on there.every thing on the truck is origanal.clutch tranny vp injectors.i also use diesel clean every tank.and sea foam here and there.never mixed the two.

any ideas?

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ok guys. so i tighted the T fitting and it starts like it should.the lower part of the T fitting was loose but not loose enough to alow fuel to seep threw.