DESCRIPTION
Air injection systems, used in many applications (may vary according to engine and equipment), are designed to reduce carbon monoxide and hydrocarbon emissions. This is done by injecting fresh air at critical points in the exhaust manifold to burn those gases which passed through the combustion cycle.
System consists of an air pump with integral filter, diverter/by-pass valve, check valve(s), external or internal injection tubing and connecting hoses. Some Ford models use additional valves, depending on applications. These valves are explained below.
AIR PUMP
The air pump uses an eccentric (off-center) vane to draw in fresh air, compress it, and force it on through the system. The pump is belt-driven. (Scheme 20)
Scheme 20
DIVERTER VALVE
Air flows from air pump into diverter valve. This valve prevents backfiring, by stopping air injection flow during periods of high increase in manifold vacuum (such as during deceleration). Diverter valve dumps air supply to atmosphere for the first few seconds of deceleration.
Most diverter valves also have built-in pressure relief valve, which bleeds off excessive air pump pressure to prevent damage to the system. Most diverter valves are similar. (Scheme 21)and (Scheme 22). Electric diverter valve is used on GM and Jeep V6 California models and is controlled by the Electronic Control Module (ECM).
Ford Motor Co. Timed By-Pass Valve
This is a normally-open valve. During normal operation, vacuum is equalized on both sides of diaphragm. Spring pressure holds valve open, allowing fresh air to the exhaust.
On deceleration, manifold vacuum pulls diaphragm, and air is directed to the atmosphere. Small orifice in diaphragm will allow pressure to quickly equalize again. (Scheme 22)
Ford Motor Co. Normally-Closed By-Pass Valve
When no vacuum is applied, all air pump air is diverted to the atmosphere to protect the catalytic converter. When vacuum is received, air then passes to exhaust ports.
Scheme 21
Ford Motor Co. Timed & Vented By-Pass Valve
Valve operation is similar to that of timed valve described earlier. When vacuum signal is 3 in. Hg or more, valve will continuously vent air pump air to the atmosphere. (Scheme 24)
POWER HEAT CONTROL VALVE (CHRYSLER MOTORS ONLY)
This vacuum-operated valve is located between right exhaust manifold and exhaust pipe. It directs majority of exhaust gas flow through left side exhaust manifold, until engine temperature reaches pre-determined point. After that temperature is reached, gas flows through both manifolds.
INJECTION MANIFOLD
Injection manifold in many applications is an external tubing system, mounted to exhaust manifold with air delivery ports for each exhaust port. It is through this manifold that air pump air reaches the exhaust system. Some applications have internal air injection system, consisting of specially drilled passages in intake manifold, which carry air pump air to exhaust ports. External tubing is eliminated.
CHECK VALVE
Check valve is a one-way flow valve. It prevents exhaust manifold air from backing up through the system and reaching air pump. Check valve will be found either in tubing, leading to injection manifold or as an integral part of manifold.
Scheme 22
Scheme 23
IDLE VACUUM VALVE (FORD ONLY WITH CATALYTIC CONVERTER)
This valve is used on Ford models which have a catalytic converter. Air injection system on these models is also tied into the EGR system. (Scheme 25)
Operating in conjunction with vacuum delay valve, idle vacuum valve provides backfire control, full-time idle air dump, cold temperature catalyst protection and cold EGR lock-out.
On long idle, air dump prevents high underbody temperatures in exhaust system.
During cold engine operation, the valve prevents air injection and EGR operation until catalyst and engine are warm.
Scheme 24
EXCESSIVE BELT NOISE
Loose pump drive belt or seized pump.
EXCESSIVE PUMP NOISE
Leak in hose or loose hose. Hose touching other engine parts. Diverter valve or by-pass valve failure. Check for valve failure, pump mounting loose, pump or impeller damaged.
NO AIR SUPPLY
Loose drive belt, leak in hose or hose fitting. Diverter valve or by-pass valve failure. Check for valve failure or pump failure.
EXHAUST BACKFIRE
Incorrect engine tune-up, engine vacuum leaks, faulty diverter valve or check valve.
Note. Proper operation of Air Injection System is dependent upon proper engine tune-up. See individual vehicle models for specifications and procedures.
DIVERTER VALVE TEST
Check valve by accelerating engine, and allowing throttle to close rapidly. Momentary rush of air should be noted at diverter air outlet.
CHECK VALVE TEST
To check operation of this valve, remove air supply hose from pump at distribution manifold. With engine operating, listen for exhaust leakage at check valve, which is connected to distribution manifold.
MAINTENANCE
Approximately every 15,000 miles, air injection system components should be checked for proper operation and condition. No regular parts replacement schedule is required. Service is limited to replacement of air pump filter, if it becomes clogged.
CENTRIFUGAL FAN FILTER
To replace, remove drive belt, pulley mounting bolts and pulley. Break off remaining portions of centrifugal fan filter from pump hub. Use care that fragments do not enter air intake hole. Install new filter by drawing it on with pulley and pulley bolts. Do not attempt to hammer or press filter on shaft.
Removing Centrifugal Fan Filter from Air Injection Pump with Pulley Removed. Scheme 25
Note. After new filter is installed, it may squeal during operation, until its outside diameter has worn in. This may require 20 to 30 miles of operation.
| CAUTION | If engine or engine compartment is to be cleaned with steam or high pressure detergent, centrifugal filter fan should be masked off to prevent liquids from entering air pump. |
EXHAUST EMISSION SYSTEM CLEANING
DO NOT attempt to clean diverter valve. Do not blow compressed air through check valve.
AIR PUMP OVERHAUL
Overhaul of air pump is not recommended, since internal components of pump are not serviceable.
AIR PUMP EXHAUST TUBE REPLACEMENT
Remove by placing tube in vise, or use pliers to pull tube with twisting motion. Insert new tube into hole, and tap in using block of wood to protect tube. Approximately 7/8" (22 mm) of tube should extend above cover.