Re: Fuel pump

Posted by HH56 On 2023/2/12 22:18:39

The solenoid or pulse pump has two valves very similar in operation to those in the mechanical pump. When the pump is operating the solenoid works a kind of diaphragm arrangement and valves are functional. If it is turned off the mechanical pump suction will just pull the valves open and fuel can flow thru the pump.

The rotary pump has a set of offset gears similar to an oil pump or some tightly fitting vanes mounted on the motor shaft which rotate in a chamber. As those turn the fuel is pulled in from one side, pushed thru the spaces between teeth in the gears or vanes in the chamber and expelled out the other side and on to the engine. Once the pump stops the gear or vane segments form a fairly tight seal so any fuel is blocked from passing thru the pump.

In order to use a rotary it usually needs a parallel path for fuel to flow. That path has a check valve in the middle. If pump is running it prevents the pressurized fuel out of the pump from flowing backwards and into the pump inlet side again. When the pump is off then the suction of the mechanical pump opens the check valve and allows fuel to flow thru that path.