ARMY TM 9-281-252-24 AIR FORCE TO 38G1-92-2 TABLE 3-2.  Troubleshooting Malfunction Test or Inspection Corrective Action a. Remove and test fuel injectors.  Refer to paragraph 3-17.  If not defective, do step 2. b. Replace fuel injector(s).  Refer to paragraph 3-17. Step 2. Check for improper fuel pump timing. a. Adjust fuel pump timing.  Refer to paragraph 3-14. b. If timing is correct, repair or replace defective engine. 12.  BLUE EXHAUST SMOKE. Step 1. Check for blocked air intake system. Remove blockage as found.  If no blockage is found, do step 2. Step 2. Check for loss in vacuum. a. Perform vacuum check.  Refer to paragraph 3-5.2. b. If vacuum is correct, do step c. c. If vacuum is not correct, repair or replace engine. Step 3. Check for defective intake or exhaust valve seals or valve guides. a. Repair or replace defective components.  Refer to paragraph 3-27. b. Disassemble and inspect valve seals and guides.  Refer to paragraph 3-27.  If not defective, repair or replace defective engine. 13.  ABNORMAL ENGINE NOISE. Step 1. Check for worn tappets. a. Inspect tappets for wear.  Refer to paragraph 3-27.  If not worn, do step 2. b. Replace worn tappets.  Refer to paragraph 3-27. 3-9