Mityvac 06820 Diesel Compression Test Adapters - Manual (Page 13)

Page Number - 13
Form 822378
temperature (195° F approx). Check
for vacuum at 3000 RPM; it should be
5 Hg minimum.
4) If no vacuum is available in step 3,
check for it between the EGR thermal
vacuum switch (TVS) and the
carburetor. If the vacuum is available
there, replace the TVS.
5) If the vacuum supply between the
EGR and the carburetor is adequate,
connect the pump to the EGR valve
inlet. Depress the valve diaphragm
and apply approximately 10” Hg of
vacuum to the EGR. Release the
diaphragm and record the time it takes
for the diaphragm to return to its
seated position.
6) If it takes less than 20 seconds for the
valve to seat, replace the valve.
GM POSITIVE BACK-
PRESSURE EGR TEST
1) Follow steps 1 through 4 of the
ported vacuum and negative back-
pressure EGR test.
2) Remove the EGR valve from the
engine. Connect the pump to the EGR
vacuum inlet and apply 10” Hg of
vacuum. The valve should not open. If
it does, replace the valve.
3) Continue the test by keeping the
vacuum applied and shooting a low-
pressure stream of air into the valve’s
exhaust inlet. The valve should now
open. If it does not, replace the valve.