1991-Montero-Service-Manual · emission control visual inspection guidelines · страница 7 из 15 · Открыть оригинал PDF ↗
Verify EGR valve is present and not modified or purposely
damaged. Ensure thermal vacuum switches, pressure transducers, speed
switches, etc., (if applicable) are not by-passed or modified. Ensure
vacuum hose(s) to EGR valve is not plugged.
Fig. 8: Typical Dual Diaphragm EGR Valve
Courtesy of General Motors Corp.
Positive Backpressure EGR (BP/EGR) Valve
This type uses both engine vacuum and exhaust backpressure to
control the amount of EGR. It provides more recirculation during heavy
engine loads than the single diaphragm EGR valve.
A small diaphragm-controlled valve inside EGR valve acts as a
pressure regulator. The control valve gets an exhaust backpressure
signal through the hollow valve shaft. This exhaust backpressure
exerts a force on bottom of control valve diaphragm. The diaphragm
plate contains 6 bleed holes to bleed air into the vacuum chamber when
backpressure valve is in open position. See Fig. 9.
Verify EGR valve is present and not modified or purposely
damaged. Ensure thermal vacuum switches, pressure transducers, speed
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