TM 10-3930-669-20 VERIFY REPAIR (1) Start engine (TM 10-3930-669-10). (2) Observe tailpipe after 10 minutes of operation. (a) If   engine   does   not   produce excessive black or gray smoke, fault corrected. (b) If  engine  produces  excessive black or gray smoke, fault not corrected.    Perform  Step  (3) below.  Repeat procedure and notify Supervisor. (3) Shut down engine. 2-81