Page 226 - 05. Subyek Teknik Mesin - Automobile Mechanical and Electrical Systems Automotive Technology Vehicle Maintenance and Repair (Vehicle Maintenance Repr Nv2) by Tom Denton

2
210 Automobile mechanical and electrical systems

Figure 2.268 Fuel pressure regulator on rail

Manifold
pressure

Fuel inlet

Fuel outlet

Figure 2.269 Fuel pressure regulator valve closed

A fuel pressure regulator is fi tted to maintain a precise pressure at the fuel
injector valve nozzles. On port fuel injection systems, a fuel rail is used to hold
Key fact the pressure regulator and the fuel feed to the injector valves ( Fig. 2.268 ). The
injector valves usually fi t directly onto or into the fuel rail. The fuel rail holds
A fuel pressure regulator is fi tted to
maintain a precise pressure at the suffi cient fuel to dampen fuel pressure fl uctuations and keep the pressure
fuel injector valve nozzles. applied at all injector nozzles at a similar level.
Fuel regulators are sealed units with a spring-loaded diaphragm and valve on
the return outlet to the fuel tank ( Figs 2.269 and 2.270 ). Fuel is pumped into the
regulator and when the pressure is high enough, it acts against the diaphragm
and compression spring to open the valve. Surplus pressure and fuel is allowed to
return to the fuel tank. Once the pressure in the fuel regulator is reduced, the valve
Key fact closes and the pressure builds up again. Throttle body injection systems operate
in the region of 1 bar, and port fuel injection systems in the region of 2.5 bar.
Throttle body injection systems
operate in the region of 1 bar, and In port fuel injection systems, the inlet manifold vacuum acts against the
port fuel injection systems in the
compression spring in the fuel pressure regulator. This is required to maintain a
region of 2.5 bar.
constant pressure differential between the fuel rail and the inlet manifold. With a
constant pressure differential, the amount of fuel delivered during a set time will
be the same irrespective of inlet manifold pressure.