Thermactor System Mercury Topaz I

DESCRIPTION

The Thermactor Exhaust Emission Control system reduces carbon monoxide (CO) and hydrocarbon (HC) content of exhaust gasses. It injects fresh air into the exhaust gas stream as it leaves the combustion chamber, allowing continued combustion of unburned gasses. A typical system consists of the following components: Air supply pump, air by-pass valve, centrifugal filter, check valve(s), air control valve, air manifold and air hoses.

Individual systems vary in number and type of components depending upon engine size and application, these are as follows: The Managed Thermactor Air (MTA) system uses the same basic components as the standard system, but "manages" thermactor air according to operating conditions. Some models are equipped with Thermactor II system which uses a pulse air valve instead of an air pump. Another system, the Extended Idle Air By-Pass System is used to dump secondary thermactor air to the atmosphere.

OPERATION

Inlet air to air pump is drawn through a centrifugal air filter fan. Air pump then supplies air under pressure to exhaust port near exhaust valve, by either an external air manifold, or through an internal drilled passage in cylinder head or exhaust manifold. Oxygen in fresh air, plus heating of exhaust gasses, cause further burning which converts gasses into carbon dioxide and water.

In Managed Thermactor Air System, air can be by-passed to atmosphere by a Thermactor Air By-Pass Valve and/or directed upstream near exhaust manifold or downstream to underbody catalytic converter by Thermactor Air Control Valve. Some models may use a Combined Air By-Pass/Air Control Valve.

In Thermactor II System, natural pulses present in exhaust system are used to pull air into exhaust manifold through a Pulse Air Valve. Pulse air valve is connected to exhaust manifold with a tube and to air cleaner with a hose.

In Extended Idle Air By-Pass System, a normally closed Idle Tracking Switch opens when throttle returns to idle, signaling EEC Module to de-energize normally closed solenoid valve. Vacuum is removed from normally closed by-pass valve, causing thermactor secondary air to be dumped into atmosphere.

AIR PUMP

Air pump is a belt-driven, positive displacement, vane type pump. It is available in 11 cu. in. and 19 cu. in. sizes. Either may be driven with different pulley ratios for different applications. Air is received from a remote silencer filter attached to the air inlet nipple of the pump. The by-pass valve performs pressure relief.

AIR BY-PASS VALVES

Two types of valves are used by Ford Motor Co., normally open and normally closed valves. In addition, these valves may be mounted in-line with air pump or mounted directly to pump.

Normally Open Valves

Normally open valves are available with and without vacuum vents. Valves without vents provide a timed dump of air for 1.1-2.8 seconds when a sudden high vacuum of about 20 in. Hg is applied to signal port. This prevents backfire during deceleration.

Normally open valves with a vacuum vent provide a timed dump during deceleration and also dump when a vacuum pressure difference is maintained between signal port and vent port. Signal port must have 3 in. Hg more vacuum than vent port to hold dump. This is used to prevent catalyst from overheating.

Normally Open Air By-Pass Valve Valve with vacuum vent shown. Scheme 24

Normally Closed Valves

Normally closed valves supply air to exhaust system with medium and high vacuum signals applied during normal operating modes, short idles, and some accelerations. With no or low vacuum applied, pump air is dumped through silencer ports of valve.

Normally Closed Air By-Pass Valve. Scheme 25

AIR SUPPLY CONTROL VALVE

Air supply control valves direct air pump output to exhaust manifold or downstream to catalyst, depending upon engine control system.

Air Supply Control Valve. Scheme 26

COMBINATION AIR BY-PASS/AIR CONTROL VALVE

Combination air by-pass/air control valve is used with some managed air thermactor systems. Valve combines functions of two normally closed valves in one unit. There are bleed type and non-bleed type valves; both look alike. Bleed type valves will have percentage of bleed molded into side of case. By-Pass portion of valve dumps air to atmosphere, while control valve portion directs air upstream or downstream.

Combination Air By-Pass/Air Control Valve Available bleeds for port "A" seat listed above. Scheme 27

CHECK VALVES

Check valves are used on all thermactor systems in various locations. These valves block air flow in one direction and allow air flow in other direction.

IDLE TRACKING SWITCH

Idle tracking switch, located on carburetor, is a mechanically operated electric switch held open by throttle linkage when throttle is closed and is used on Extended Idle Air By-Pass System.

When idle tracking switch is opened, EEC Module is signaled to de-energize normally closed solenoid. When this happens, vacuum is removed from normally closed by-pass valve and causes thermactor air to be dumped into atmosphere.

PULSE AIR VALVE

Pulse air valve replaces air pump on some thermactor systems. It permits air to be drawn into exhaust system on vacuum exhaust pulses and blocks backflow of high pressure exhaust pulses. Fresh air completes oxidation of exhaust gas components.

Pulse Air Valve. Scheme 28

DUAL THERMACTOR AIR CONTROL SOLENOID VALVE ASSEMBLY

Dual thermactor air control solenoid valve assembly consists of 2 normally closed solenoid valves with vents; one controls thermactor air by-pass valve and other controls thermactor diverter valve. Both valves should pass air when de-energized and not when energized.

ANTI-BACKFIRE VALVE

Anti-backfire valve, located downstream from air by-pass valve, diverts a portion of thermactor air to intake manifold during periods of sudden decrease of intake manifold pressure.

AIR SILENCER

Air silencer, mounted in engine compartment, is a combination silencer and filter for pulse air system or for an air supply pump not equipped with impeller type centrifugal air filter fan. It is connected to the system by means of a flexible hose.

ELECTRONIC CONTROL ASSEMBLY

Electronic Control Assembly (ECA), located in dash or under front passenger seat, is center of EEC IV System. It receives information from many sensors, evaluates data, and sends signals to various relays, solenoids, and other actuators.

THERMACTOR IDLE VACUUM VALVE

Thermactor Idle Vacuum Valve (TIV) vents vacuum signal to atmosphere when preset manifold vacuum or pressure is exceeded. During periods of extended idle conditions, this valve is used to divert thermactor air flow to limit exhaust temperature and to cut EGR in a heavy boost mode for turbocharged applications.

Check belt tension and adjust to specifications. Disconnect air supply hose from control valve. Observe air flow from pump outlet with engine running. Flow should increase as engine speed is increased.

Normally Open Valve Without Vacuum Vent

1. With engine at normal operating temperature, parking brake applied and transmission in "P" or "N", disconnect air supply line at valve outlet. Disconnect vacuum line at vacuum nipple and vacuum vent.
2. With engine at 1500 RPM, air should be heard and felt at valve outlet. Connect a direct vacuum line from any manifold vacuum source to vacuum nipple on valve. Air at outlet should be momentarily decreased. Air pump supply air should be heard at silencer ports.
3. Reconnect vacuum and thermactor lines. If valve fails any test and air pump checks okay, replace valve.

Normally Open Valve With Vacuum Vent

1. With engine at normal operating temperature, parking brake applied and transmission in "P" or "N", disconnect air supply line at valve outlet. Disconnect all vacuum lines from vacuum nipple and vent.
2. With engine at 1500 RPM, air pump supply should be heard and felt at outlet. Connect a vacuum line from vacuum nipple to one of vacuum fittings on intake manifold. With vacuum vent open to atmosphere and engine at 1500 RPM, no air should be felt at outlet and all air should be by-passed through silencer ports.
3. Using same direct line to an intake manifold vacuum source, cap vacuum vent. Increase engine speed to 2000 RPM and suddenly release throttle. A momentary interruption of air pump supply should be felt at valve outlet.
4. If valve fails any test and air pump is operating okay, replace valve. Reconnect all vacuum and thermactor lines.

Normally Closed Valve

1. With engine at normal operating temperature, parking brake applied and transmission in "P" or "N", disconnect air supply line at valve outlet. Remove vacuum line and ensure that a vacuum signal is present at nipple.
2. Remove any delay valves or restrictors in line. Vacuum must be present at nipple before proceeding. With engine at 1500 RPM, and vacuum line connected to nipple, air pump supply air should be heard and felt at outlet.
3. With engine at 1500 RPM, disconnect vacuum line. Air at outlet should be significantly decreased or shut-off. Air pump supply air should be heard or felt at silencer ports.
4. If valve fails any test, and air pump is operating okay, replace valve. Reconnect all vacuum lines.

1. With engine at normal operating temperature, parking brake applied and transmission in "P" or "N", disconnect hoses from ports "A" and "B". (Scheme 27) Disconnect and plug line to port "D". With engine at 1500 RPM, air should flow from by-pass vents.
2. Reconnect line to port "D". Disconnect and plug line to port "S". Ensure vacuum is present in line to port "D". With engine at 1500 RPM, air should flow from port "B", and no air should flow from port "A".
3. Apply 8-10 in. Hg vacuum to port "S". With engine at 1500 RPM, air should flow from port "A". If valve has a vacuum bleed, some lesser amount of air will flow from port "A" or "B" and main discharge will change when vacuum is applied to port "S".
4. If valve fails any test, replace valve. Reconnect hoses.

1. Verify that air is being supplied to valve inlet by disconnecting inlet supply hose. Disconnect hoses at valve outlets "A" and "B" and vacuum nipple. Some air flow should be heard and felt at valve outlet "B" and little or no air at valve outlet "A" with engine at 1500 RPM.
2. Using a direct vacuum line from manifold vacuum source, connect line to vacuum nipple. An increase in air flow should be detected at valve outlet "A" and little or no air at valve outlet "B". If valve fails any test, replace valve. Reconnect all lines.

VACUUM CHECK VALVE

Apply 16 in. Hg vacuum to check side of valve and trap. If vacuum remains above 15 in. Hg for 10 seconds, valve operation is normal. If not, replace valve.

When throttle stop lever is against idle tracking switch, switch is open and there should be no continuity.

EXTENDED IDLE AIR BY-PASS SYSTEM

1. With engine at normal operating temperature and transmission in "N", begin timing. If after 2 1/2 minutes thermactor by-pass valve dumps secondary air through vents, system is okay. If not, check routing and condition of hoses. If hoses are okay, check by-pass valve function.
2. If valve is okay, check battery voltage to ITS and continuity through normally closed ITS while manually cycling switch. If okay, check that solenoid is functional and actually opens to close off vacuum. If solenoid is okay, turn engine "OFF" and ignition "ON". After 2 1/2 minutes, check vacuum signal to solenoid.

With engine at normal operating temperature and curb idle, a suction should be felt at valve inlet. If not, replace valve.