TM 10-3930-669-34 4. EXCESSIVE BLACK OR GREY SMOKE (CONT). KNOWN INFO TEST OPTIONS Injection pump OK. Compression test. Injection pump timing OK. STE/ICE-R #50. POSSIBLE PROBLEMS REASON FOR QUESTION Low engine compression. If engine compression is low, Valves or valve springs faulty. engine will exhaust black or Piston ring(s) faulty. grey smoke excessively. 2-42