Pontiac Fiero 1988 Service Manual page 684

D R I V E A B I L I T Y A N D E M I S S I O N S - F U E L INJECTION ( P O R T ) 6 E 3 - C 3 - 1
SECTION C3
EVAPORATIVE EMISSION C O N T R O L S Y S T E M (EECS)
CONTENTS
o o o o <
GENERAL DESCRIPTION .
P U R P O S E • • • • • • • • • • • • • • • » « • • • «
E V A P O R A T I V E E M I S S I O N S Y S T E M . . .
RESULTS O F I N C O R R E C T O P E R A T I O N
DIAGNOSIS
• • • •
C3-1
C3-1
C3-1
C3-1
C3-1
V I S U A L C H E C K O F C A N I S T E R C3-1
GENERAL DESCRIPTION
PURPOSE
The basic Evaporative Emission Control System
(EECS) used on all vehicles is the charcoal canister
storage method. This method transfers fuel vapor from
the fuel tank to an activated carbon (charcoal) storage
device (canister) to hold the vapors when the vehicle is
not operating. When the engine is running, the fuel
vapor is purged from the carbon element by intake air
flow and consumed in the normal combustion process.
E V A P O R A T I V E E M I S S I O N S Y S T E M
This system uses a canister with an integral
diaphragm operated purge valve. The fuel vapors
vent from the vapor storage tank to the canister.
When the engine is running, manifold vacuum is
supplied to the top tube of the purge valve (Control
Vacuum Signal) which lifts the valve diaphragm and
opens the valve. The lower Tube on the purge valve
(PCV Tube) is connected to a timed port above the
throttle valve. The rate of purge is controlled through
this port by throttle location.
To increase the capacity of the fuel tank there is a
vapor storage tank located near the fuel tank.
RESULTS OF INCORRECT OPERATION
Evidence of fuel loss or fuel vapor odor can be
caused by:
Liquid fuel leaking from fuel lines, fuel pump,
or fuel rail,
Inoperative purge valve,
Disconnected, misrouted, kinked, deteriorated
or damaged vapor hoses, or control hoses.
Poor idle, stalling, and poor driveability can be
caused by:
Inoperative purge valve,
Damaged canister,
Hoses split, cracked and or, not connected to
the proper tubes.
F U N C T I O N A L TESTS . <> * * . . • * * . o * <, <> <> o * C3-2
C a n i s t e r P u r g e V a l v e
* * * o • * » < , <> * * * o o C3°2
O N - C A R S E R V I C E . . . . . . . . . . . . . . C3-2
F U E L V A P O R C A N I S T E R • . . o * . . * . . . o
0
» * C3-2
P A R T S I N F O R M A T I O N . . . . . . . . . . . . . . . . . C3-2
o
PCV
CONTROL V A C U U M
F U E L T A N K
PURGE VALVE
5-28-85
* 6 S 28Q8-6E
F i g u r e C3-1 - V a p o r C a n i s t e r
DIAGNOSIS
V I S U A L C H E C K O F C A N I S T E R
• Cracked or damaged, replace canister.
• Fuel leaking from bottom of canister, replace
canister and check hoses and hose routing.
• Check filter at bottom of canister. If dirty,
plugged, or damaged, replace
filter.