Sounds like expected operation to me. WeeWX records rainfall on a per-period basis; so an archive record (or for that matter a loop packet) should contain the total rainfall recorded for the period covered by that archive period (or since the last loop packet for loop packets). The field map in an import config file determines which source data is mapped to which WeeWX field and for each field the
is_cumulative config option determines whether the source data is a cumulative value or not. If
is_cumulative is set
True the imported value is the difference between successive values. The default value for
is_cumulative is
False, but the example import config file has
is_cumulative set
True for the example rainfall entry (as experience shows most csv imports use a cumulative rainfall value).
Without knowing the nature of your source data, the field map config for your rainfall field and what is actually imported into your archive (you say 'no data is imported' - does the mean the value zero was the result or there is no data at all (the two are quite different)) it's impossible to say what is wrong, if anything at all. If the above does not explain what you are seeing please post an extract of your source data, your import config file and an extract of the imported data (covering the source data extract provided) and we will see what is going on.
Gary