Ninety-Eight FWD V6-181 3.0L (1985)
Distributor Thermal Vacuum Switch: Description and Operation
Choke Vacuum Break Distributor Thermal Vacuum Switch
This switch is located in the air cleaner and permits the choke to run richer below the switching point, then to the leanest point above the switching
point. The distributor vacuum advance receives full manifold vacuum below the switching point of the CVB-DTVS. When temperatures exceed the
calibration value of the switch, manifold vacuum is directed to the thermostatic air cleaner and choke vacuum break ports while the port to the vacuum
advance is blocked, preventing distributor advance above the switching point.
Dist. Spark/Canister Purge Thermal Vacuum Switch (DS-CP-TVS)
The two upper ports and the two lower ports of this valve are sealed when cold and connected to each other when warm. The two upper ports are not
connected to the two lower ports.
Dist. Thermal Vacuum Switch (EGR-EFE-EMR-DTVS)
When engine coolant temperature is below the calibration value of the switch, the EFE valve actuator and the EMR vacuum switch receive manifold
vacuum from port 2, which is directed through the TVS from port 1. Port 3 is vented through port 6 while ported vacuum at port 4 and the distributor
ports are sealed.
When engine coolant temperature is above the switching point, distributor port 5 receives vacuum from port 1; the EFE actuator and the EMR vacuum
switch are vented at port 6; while port 3 receives ported vacuum from port 4.
Distributor Spark Thermal Vacuum Switch (DS-TVS)
This switch allows no vacuum flow to the distributor when engine coolant temperature is below the calibration temperature. When engine coolant
temperature is above the calibration temperature, the DS-TVS allows ported vacuum to the distributor. The ported vacuum signal is controlled by a
distributor spark vacuum delay valve (DS-VDV) which maintains vacuum advance during rapid throttle openings, thereby improving engine response
during cold engine operation.
Distributor Spark Thermal Vacuum Valve (DS-TVV)
This valve supplies manifold vacuum through a distributor spark vacuum delay valve (DS-VDV) to the distributor when the carburetor air inlet
temperature is below the specified temperature. The DS-VDV maintains vacuum advance during rapid throttle opening to improve engine response
during cold engine operation. When engine coolant temperature is above the calibration temperature, ported vacuum is supplied to the distributor
through a distributor spark thermal vacuum switch (DS-TVS) with no additional vacuum controls.
Distributor Thermal Vacuum Switch (EGR-EMR-DTVS)
When engine coolant temperature is below the switching point, this switch receives manifold vacuum from port 2, which is directed through the TVS
from port 1. Port 3 is vented through port 6 while ported vacuum at port 4 and distributor ports are sealed.
When engine coolant temperature is above the switching point, the distributor port 5 receives manifold vacuum from port 1. Port 2 is now vented
through port 6, while port 3 receives ported vacuum from port 4.
Early Fuel Evap/Dist. Thermal Vacuum Switch (EFE-DTVS)
The EFE-DTVS is an engine coolant sensitive vacuum switch which controls vacuum to both the distributor and EFE valve. When engine coolant
temperatures are below the calibration point of the switch, manifold vacuum is directed to the EFE system and the distributor vacuum advance is vented
to atmosphere. When engine coolant temperatures are above the calibration point of the switch, the EFE actuator is vented to atmosphere while the
distributor receives ported vacuum for proper spark advance.
TAC/Distributor Thermal Vacuum Switch (TAC-DTVS)
When TAC inlet air temperature is below the switching point, vacuum from the carburetor port is directed to the distributor vacuum advance and the
TAC sensor. Above the switching point, vacuum is directed to the TAC sensor but not to the distributor vacuum advance.
