The issue is that you're using the | (pipe) character instead of the , (comma) character in your SQL statement. change all "|" to "," in the SQL statement and you should be fine.
$import="INSERT into products(PID,pName,mID,pMerchant,pLink,pThumb,pImage,pPrice,pRetailPrice,pMainCat,pSubCat,pDescription,pCustom1,pCustom2,pCustom3,pCustom4,pCustom5,LastUpdate) values('$data[0]', '$data[1]', '$data[2]', '$data[3]', $data[4]', '$data[5]', '$data[6]', '$data[7]', '$data[8]', '$data[9]', '$data[10]', '$data[11]', '$data[12]', '$data[13]', '$data[14]', '$data[15]', '$data[16]', '$data[17]')";