Typically fuel tanks are usually mounted at least two feet below and ten feet away from the fuel pump. This configuration creates multiple problems associated with the fuel delivery to the engine. First, the injection pump has to draw the fuel from the tank by creating a vacuum. When diesel fuel is drawn by a vacuum fuel vapor is produced. Second, while the vehicle is underway the fuel is sloshing around in the fuel tanks creating entrained air. This circumstance has created a situation far from the manufacturer test cell conditions which results in air and vapor being mixed in with the fuel when it is delivered to the injector. By having entrained air and air vapor in the fuel the engine does not perform at the engine manufacturer's specification. Air and fuel vapor occupy the space that should have pure fuel, thus delaying the injection of fuel into the combustion chamber. This phenomenon is better known as "RETARDED TIMING." Air/vapor present in fuel is very inconsistent also causing varying degrees of changes in injection timing.
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