Equus 3660 - Hand Vacuum Pump & Brake Bleeding Kit - Manual (Page 14)

12 3660
B. TROUBLESHOOTING
NOTE: EGR systems vary greatly between vehicle makes and models.
The following paragraphs provide general testing and troubleshooting
procedures for EGR systems. For specific tests for your vehicle, refer to
the manufacturer's service manual.
A defective EGR valve generally remains either fully closed or fully
open. An EGR valve which remains closed will increase NOx emissions.
An EGR valve which remains open will cause the engine to stall at idle,
to idle roughly, to lose power, or to run rough at full throttle.
An EGR valve may fail as a result of one or more of the following
causes:
• Loss of vacuum or control vacuum
• Mechanical defect (such as a ruptured diaphragm)
• Contamination of or damage to the valve seat (restricted by carbon
buildup)
• Restrictions in the exhaust tube
C. TESTING EGR VACUUM/ EGR CONTROL SYSTEM
1. Connect the vacuum pump's vacuum port to the EGR valve's
vacuum supply line (use the vacuum tee included in the accessory
kit, if necessary).
2. Start and run the engine until it reaches normal operating
temperature.
3. Increase engine speed to approximately 2000 ~ 2500 RPM and
observe the vacuum gauge.
• The EGR valve vacuum supply should be at least 4 ~ 6 in. (10
~ 15 cm) Hg of vacuum.
• If no vacuum is present, check the vacuum hoses and
connections that supply vacuum to the EGR valve for any
abnormality or defect. Repair as necessary.
• If vacuum hoses are in good condition, test the control system
that modulates and controls the vacuum to the EGR valve .
(Control systems and testing procedures vary widely
depending on the make, year and model of the vehicle. Consult
the manufacturer's service manual for testing procedures.)