DIRECT FUEL INJECTION
Page 3B-43
90-888438 JUNE 2002
Air Pressure Regulator
The air pressure regulator is located on the port fuel rail.
57980
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.
Is air pressure within 78 to 82 psi range at neutral idle psoition?
Yes
Air regulator is OK
No
Less than 78 psi? Greater than 82 psi?
Remove air regulator and clamp.
Inspect air regulator o-ring.
Remove air bypass hose from
exhaust adaptor and measure
air pressure at neutral idle condition.
Plugged bypass circuit in adaptor plate.
air pressure is less than 78 psi?
Air regulator o-ring OK and
Air pressure normal – 78 to 82 psi?
Air pressure greater
than 82 psi?
Failed air regulator.
Air exiting air bypass?
Yes?
No?
or outlet or failed compressor
Obstruction at compressor inlet
Failed air regulator.
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