| Share | Phrase |
|---|
| 22.16% | prevent back flow [perform operation] |
| 18.79% | bp [location] prevent back |
| 16.84% | valve [does] prevent back |
| 10.28% | crankcase [location] prevent back |
| 9.09% | prevent back drive [perform operation] |
| 7.78% | prevent back fuel [perform operation] |
| 5.67% | method [does] prevent back |
| 4.86% | substantially [degree] prevent back |
| 4.47% | chamber [location] prevent back |