acceleration trouble

[gilbertmonchat]

hi,
my brother have a problem with his truck, sometime his 6.5 td stall in acceleration after he full his tank, but no problem to be restart, he have a FSD cooler, a new fuel filter, he repare the connector of the lift pump (corrosion), new oil pressure switch and he have no engine code. but he find he have some negative pressure inside is tank ( pusssss) when opening his tank , but he don't know if it's ok or not ..
tanks for your help......
his truck 98 gmc k3500 6.5 turbodiesel

[JohnC]

It's easy to confuse pressure and vacuum in the tank. Regardless, try running with the cap loose and see if the problem goes away.

How long after filling the tank does he have the problem?

[gilbertmonchat]

he can run 3 or 4 days before he have some trouble ,but sometime after 1 hour , some other time he have that trouble after he stop his truck himselve to do shopping, or go to school, and when he restart the engine have esitation and stall, ...for the cap he try one day but the fuel go out . cap loose to much because of the vibration. sorry for my english