Hi I have attached a quote from another user of this forum about this issue to show you what kind of things I have read. I couldn't get the whole quote to paste over but if you search the heading below u can see it all.
Diesel Sorento Tank Delamination
Hi Everyone Applicability: All 1st Generation Diesel Sorentos 2002 to 2010 Bad News: this problem can result in many different symptoms ranging from non-starting, to poor starting, erratic running, loss of power or sudden engine stop at speed. Good News: Kia Main Dealers are replacing the fuel tank and flushing the fuel systems FOC. BUT, some dealers are insisting on an Inspection Charge to check your tank. If the problem is confirmed then that charge should become payable by Kia.