'Tis those return lines that bedevil the C310 by only going to the mains.On anything other than the b@stard child of a Cessna fuel system they go back to all tanks.
With the mixture in ICO fuel goes from the tanks to the fuel metering system only and is then returned to the tanks. So by running the pumps you will get cold fuel from the tanks in the lines up to the fuel metering unit. Once done a brief run of the aux boost pumps will then put cold fuel in the fuel pumps and injector lines making the start so much easier.
With Lycomings there is no such fuel return line so once fuel has vaporised in the lines, pumps and injector lines making the hot start on such things as Chieftains an art form.
In summary, Contis' take more fuel than they need and return the unwanted to the tanks. Lycomings take what they need so no need for the return lines.