passing tables name into a cursor

Im having a problem changing several cursors in a function to use a passed
in child table name. Database is 8.4.3 on Linux
--Original cursor

c_runway18a cursor is

( select id, geom
, way_num as waydesignator, status_d as status
, t_width as width
, t_len as length
, coalesce(type_d,'X') as type
from v_features
where f_type = ' || feature_type and transaction_id = ' || id );

-- Modified cursor

SQL_18a text :='select id '
|| ' , geom '
|| ' , way_num as waydesignator '
|| ' , status_d as status '
|| ' , t_width as width '
|| ' , t_len as length '
|| ' , coalesce(type_d,''X'') as type '
|| ' from ' ||v_features_child
--the table is a child table, so I have to passed in to the function so
it will use indexes
|| ' where f_type = ' || feature_type
|| ' and transaction_id = ' || id ;

c_18a cursor is execute SQL_18a ;
-- this works on 9.1 Windows, but when I compile it on a 8.4.3 system I
get the following error

psql:val_ways.sql:756: ERROR: syntax error at or near ":"
LINE 1: execute $1
^
QUERY: execute $1
CONTEXT: SQL statement in PL/PgSQL function "val_ways" near line 26

I have tried "c_18a cursor is SQL_18a" without the execute clause, with
single quotes and ':' and get the same general error "QUERY: $1" .
Any thoughts?