Air Pressure Regulator; Air Regulator Troubleshooting - Mercury Optimax 250 Manual

Air Pressure Regulator

The air pressure regulator is located on the port fuel rail.
The air pressure regulator is designed to limit the air pressure inside the rails to approxi-
mately 80 psi.
The air regulator uses a spring (pressure) to control the air pressure. This spring (80 psi)
holds the diaphragm against the diaphragm seat. The contact area blocks (closes) the
air inlet passage from the excess air, return passage. As the air pressure rises (below the
diaphragm), it must reach a pressure equal to or greater than the spring pressure holding
the diaphragm closed. Once this pressure is achieved, the spring compresses, allowing
the diaphragm to move. The diaphragm moves away from the diaphragm seat, allowing
air to exit through the diaphragm seat, into the excess air passage leading to the air ple-
num.

Air Regulator Troubleshooting

Air pressure should be measured at the air schrader valve located near the middle of the
port fuel rail assembly.
Less than 78 psi?
Remove air regulator and clamp.
Inspect air regulator o-ring.
Air regulator o-ring OK and
air pressure is less than 78 psi?
Air exiting air bypass?
Yes? No?
Failed air regulator.
90-888438 JUNE 2002
Is air pressure within 78 to 82 psi range at neutral idle psoition?
No
Greater than 82 psi?
Remove air bypass hose from
exhaust adaptor and measure
air pressure at neutral idle condition.
Air pressure normal – 78 to 82 psi?
Plugged bypass circuit in adaptor plate.
Obstruction at compressor inlet
or outlet or failed compressor
DIRECT FUEL INJECTION
57980
Yes
Air regulator is OK
Air pressure greater
than 82 psi?
Failed air regulator.
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