The crank sensor will not cause low compression. If the valves have been redone in the heads and you have low compression, try a wet compression test. That is where you shoot a few shots of oil in the cylinder and then check for compression. If the compression increases, the rings are bad. If it is still low, the valves or a headgasket could be the issue.
Thursday, July 18th, 2013 AT 6:40 PM