Re: 1937 Packard 12 still not running right

Posted by HH56 On 2015/10/17 18:42:33

Flow thru rotaties really depends on the pump construction. On some of the roller rotaries and rotary vane types, as long as the pump is off and spring pressure or centrifugal force is not keeping the vanes tight to the cavity wall there is enough space between the vane and side walls that some fuel can get pulled past -- albeit not at full flow. On the gearrotor types there is generally minimal to no clearance and fuel is totally blocked unless pump is running.

The use of a check valve and tee setup is recommended for rotaries in series. In that setup a checkvalve parallels the pump. The mechanical pump can still pull fuel thru the checkvalve and the pump (if it lets any fuel pass) for complete flow yet when the electric pump is on the checkvalve closes so fuel cannot go back into the tank and has to go to the fuel line.