I use it like this, and it works without any truncation.
Dim da As New OleDbDataAdapter("select * from [x.txt]", "Provider=Microsoft.Jet.OLEDB.4.0;Data Source=c:\;Extended Properties=""text;HDR=No;FMT=Delimited""")
Dim ds As New dataset
da.Fill(ds)
contents in c:\x.txt
---------------------
1,prerak,400,12.50
2,patel,500,12.00