Thermactor System Ford LTD Crown Victoria I

DESCRIPTION

The Thermactor Exhaust Emission Control system reduces carbon monoxide (CO) and hydrocarbon (HC) content of exhaust gases. It injects fresh air into the exhaust gas stream which continues combustion of unburned gases. A typical system consists of an air supply pump, air by-pass valve, centrifugal filter, check valve(s), air control valve, air manifold and air hoses.

Individual systems may vary in number and type of components, depending upon engine size and application. 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 the Thermactor II system. It uses a Pulse Air Valve (PAV) instead of an Air Pump. Another system, the Extended Idle Air By-Pass system, is used to release secondary thermactor air to the atmosphere.

OPERATION

The air pump supplies air under pressure to the exhaust port near exhaust valve by either an external air manifold, or through an internal drilled passage in cylinder head, or exhaust manifold. This pressurized air, combined with hot exhaust gases, creates a secondary combustion stage which produces carbon monoxide and water.

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

In the Thermactor II system, natural pulses present in the exhaust system are used to pull air into exhaust manifold through a Pulse Air Valve (PAV). The pulse air valve is connected to exhaust manifold by a tube, and to air cleaner by a hose.

In the Extended Idle Air By-Pass System, a normally closed Idle Tracking Switch (ITS) opens when throttle returns to idle. This signals the EEC module to de-activate the normally closed solenoid valve. Vacuum is removed from the normally closed by-pass valve, causing thermactor secondary air to be released into atmosphere.

AIR PUMP

The air pump is a belt-driven, positive displacement, vane type pump. It is available in 11 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 air inlet nipple of pump. The by-pass valve performs pressure relief.

AIR BY-PASS VALVES

The 2 types of air by-pass valves are those normally open and those normally closed. These valves may be mounted in-line or directly to air pump.

Normally Open Valves

Normally open valves are available with or without vacuum vents. Valves without vents release air for 1.1-2.8 seconds when a sudden high vacuum of about 20 in. Hg is applied to the signal port. This prevents backfiring during deceleration.

Normally open valves with a vacuum vent release air at intervals during deceleration, and when a vacuum pressure difference is maintained between signal port and vent port. The signal port must have 3 in. Hg more vacuum than vent port. The pressure difference, along with timed release of air during these stages, prevents catalyst from overheating.

Scheme 26

Normally Closed Valves

Normally closed valves supply air to exhaust system by applying medium and high vacuum signals during normal operating modes, short idles, and some accelerations. With low vacuum applied, pump air is released through silencer ports of valve.

Scheme 27

AIR SUPPLY CONTROL VALVE

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

Scheme 28

COMBINATION AIR BY-PASS/AIR CONTROL VALVE

The combination Air By-Pass/Air Control valve is used with some MAT systems. The valve combines functions of 2 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 rating molded on side of case. The by-pass portion of valve releases air into atmosphere, while control valve portion re-directs air.

Scheme 29

CHECK VALVES

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

IDLE TRACKING SWITCH

The Idle Tracking Switch (ITS), located on carburetor, is a mechanically operated electric switch held open by throttle linkage when throttle is closed. It is used on the Extended Idle Air By-Pass System.

When ITS is opened, EEC module is signaled to de-activate the normally closed solenoid. When this happens, vacuum is removed from the normally closed by-pass valve, and thermactor air is released into atmosphere.

PULSE AIR VALVE

The Pulse Air Valve (PAV) replaces the air pump on some thermactor systems. It permits air to be drawn into exhaust system by vacuum exhaust pulses. This allows fresh air to complete oxidation of exhaust gases, and it blocks backflow of high pressure exhaust pulses.

DUAL THERMACTOR AIR CONTROL SOLENOID VALVE ASSEMBLY

The dual Thermactor Air Control Solenoid Valve assembly consists of 2 normally closed solenoid valves with vents; one controls Thermactor Air By-Pass Valve, and the other controls Thermactor Diverter Valve. Both valves pass air when de-activated, and do not pass air when activated.

Scheme 30

ANTI-BACKFIRE (GULP) VALVE

The Anti-Backfire Valve, located downstream from the Air By-Pass Valve, diverts a portion of thermactor air to intake manifold during periods of sudden decrease of intake manifold pressure.

AIR SILENCER

The Air Silencer, mounted in engine compartment, is a combination silencer and filter for the Pulse Air (PA) system, or for an Air Supply Pump not equipped with an impeller type centrifugal air filter fan. It is connected to system by means of a flexible hose.

ELECTRONIC CONTROL ASSEMBLY

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

THERMACTOR IDLE VACUUM VALVE

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

Check belt tension and adjust to specification. Disconnect air supply hose from control valve. Observe airflow 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 Park or Neutral, 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 functions properly, replace valve.

Normally Open Valve With Vacuum Vent

1. With engine at normal operating temperature, parking brake applied, and transmission in Park or Neutral, 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 speed at 1500 RPM, no air should be felt at outlet, since all air is 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 properly, replace valve. Reconnect all vacuum and thermactor lines.

Normally Closed Valve

1. With engine at normal operating temperature, parking brake applied, and transmission in Park or Neutral, 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 speed 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 properly, replace valve. Reconnect all vacuum lines.

1. With engine at normal operating temperature, parking brake applied, and transmission in Park or Neutral, disconnect hoses from ports "A" and "B". (Scheme 29) Disconnect and plug line to port "D". With engine speed 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 speed 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 speed 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, it must be replaced. Reconnect all vacuum hoses.

1. Verify that air is being supplied to valve inlet by disconnecting inlet supply hose. Disconnect hoses at valve outlets "A", "B", and at vacuum nipple. With engine speed at 1500 RPM, some airflow should be heard and felt at valve outlet "B", and little or no air at valve outlet "A".
2. Using a direct vacuum line from manifold vacuum source, connect line to vacuum nipple. An increase in airflow 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.

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

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 releases secondary air through vents, system is operating properly. If not, check routing and condition of hoses, and of By-Pass Valve.
2. If valve is operating correctly, check battery voltage to ITS. Also check for continuity through normally closed ITS while manually cycling switch. If correct, check that solenoid is functional and actually opens to close off vacuum. If solenoid is okay, turn engine off. Turn ignition switch to "ON" position. After 2 1/2 minutes, check vacuum signal to solenoid.