Fuel Cooler; Fuel Regulator - TOHATSU MFS25 Service Manual

Fuel System (Fuel Injection)

3) Fuel Regulator

Fuel regulator located on the upper section of vapor separator serves to keep regular fuel pressure.
Fuel regulator consists of diaphragm with built in spring that actuates valve/seat, and returns (pressurized) excessive fuel
to vapor separator when the pressure exceeds certain value.
Excessive fuel is returned to vapor separator through internal pipe below fuel level to prevent it from bubbling.
Spring side a of diaphragm is open to air so that change of atmospheric pressure is applied to diaphragm.
a To Bottom Cowl (open to air)
b High Pressure Fuel from Fuel Cooler
c Excessive fuel returns to vapor separator.

4) Fuel Cooler

Fuel cooler (heat exchanger) is connected between vapor separator and high pressure fuel filter, and uses engine cooling
water to cool high pressure fuel to fuel injector and excessive fuel to vapor separator. It serves to prevent fuel vapor lock
and fuel feed pump (FFP) from wear by removing heat from circulating excessive (high pressure) fuel.
a Fuel from Vapor Separator/FFP
b Fuel to High Pressure Fuel Filter
c Cooling Water from Cylinder Block
d Cooling Water to Check Port
4-24
a
b
a
d
b
c
c
25/30 2006