Since you are using your own delimiter, format parameter should be 6 and not 1. Refer to the code below
ExcelObj.Workbooks.Open(FI.FullName, 0, true, 6, "","",false, Microsoft.Office.Interop.Excel.XlPlatform.xlWindows, "|", true, false, 0, true,false, false);
Workbooks.Open Method
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