Additionally, in older vehicles, the fuel pump was placed outside of the fuel tank, and the intake to the fuel pump was another place in which negative pressure was needed to pull the fuel through the system, and thus potentially the site for vapor lock.
Thus, in places where E10 blends are permitted to have a higher vapor pressure than gasoline fuels, they may be more likely to cause problems with vapor lock under hot weather conditions.
There has been some consideration of the specific location within the fuel system where vapor lock might occur.
The graph suggests that fuel is commonly at temperatures where the vapor pressure is greater than the system pressure; hence, there is potential for vapor lock.
It is not clear at what ratio of fuel vapor pressure to fuel system pressure that vapor lock becomes problematic, but this has typically been addressed as an allowable temperature at which the V/L ratio reaches a certain level.
Thus, this correlation suggests that the primary site for vapor lock is in the fuel rail or injector.
Vapor lock is the apparent cause of poor HWD, but there is conflicting evidence in the literature as to where in the fuel system it occurs, whether in the fuel pump or downstream of the fuel pump in the fuel line or injector.
Two, the fact that vapor lock is a real issue that needs to be addressed and resolved.
Our fuel cooler has an internal bypass for fuel return (so a tank return is not needed) and the fuel is cooled by sea water (to alleviate vapor lock problems).