Hot Engine Test

Fig. 52 Checking For Vacuum To The EGR Valve:

NOTE: Engine should be at normal operating temperature

1. Disconnect the #16 vacuum hose from the EGR valve and connect a vacuum gauge to the hose, Fig. 52.
2. Start the engine and warm up to normal operating temperature (cooling fan should cycle ON and OFF at least once).
3. Remove the vacuum control box, and open the lid.

Fig. 53 Plugging Hose To The Purge Cut-Off Solenoid Valve:

4. Remove the top hose from the purge cut-off solenoid valve and cap the solenoid valve, Fig. 53.

Vacuum readings should be as follows:

Idle:
No vacuum

3000 rpm:
2 - 6 in Hg

3000 rpm (with blocked vacuum bleed):
Less than 2 in. Hg

Rapid acceleration:
2 - 6 in. Hg

Deceleration:
No vacuum

5. If vacuum is available at idle:
a. Check the vacuum hoses for proper routing and connections.
b. Check for correct idle speed and idle mixture and adjust as necessary.
6. If there is no vacuum at 3000 rpm or when accelerating, check the purge cut-off solenoid valve.
7. If vacuum is greater than 2 in. Hg at 3000 rpm with the blocked vacuum bleed, replace the EGR valve and check the vacuum hoses for proper routing and connections.