Chapter 6 Emissions control systems
3.OL Engine,
I .I
3.38 Detach the vacuum hose from the throttle body purge hose
nipple and connect a hand-held vacuum pump in its place
(fuel-injected models)
38 Detach the vacuum hose from the throttle body purge hose nipple and
connect a hand vacuum pump in its place (see illustration).
39 Start the engine and verify that, after the engine rpm is raised by rac-
ing the engine, vacuum remains fairly constant.
40 If there’s no vacuum created, the throttle body port may be clogged
and require cleaning.
Purge control solenoid valve (fuel-injected models)
Refer to illustration 3.4 1
41 Detach the vacuum hose with the red stripe from the solenoid valve
and attach a hand-held vacuum pump in its place (see illustration).
3.41 Detach the vacuum hose with the red stripe from the
solenoid valve and attach a hand-held vacuum pump in its place
(fuel-injected models)
42 Unplug the electrical connector from the solenoid valve.
43 Apply battery voltage (or any 12V DC source) to the purge control so-
lenoidvalve. apply a vacuum and verify that the valve leaks vacuum when
voltage is applied; when voltage is discontinued, the valve should main-
tain vacuum.
44 Measure the resistance between the terminals of the solenoid valve
and compare your reading to the range of acceptable resistance listed in
this Chapter’s Specifications.
45 If the purge control solenoid valve fails either of these tests, replace it.
4 Jet air system (carbureted models only)
Refer to illustration 4.1
1 The jet air system (see illustration) utilizes an additional inlet valve
(jet valve) whrch provides for air, or a super lean mixture, to be drawn from
the air intake into the cylinder. The jet valve is operated by the same cam
as the inlet valve. They use a common rocker arm so the jet valve and the
inlet valve open and close srmultaneously.
2 On the intake stroke of the engine, fuel/air mixture ffows through the
intake ports into the combustion chamber. At the same time, jet air is
forced into the combustion chamber because of the pressure difference
between the jet intake in the throttle bore and the jet valve in the cylinder as
Carburetor
Primary
throttle valve
\ \
4.1 Jet air system
A piece
Jet air
intake
opening
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