DESCRIPTION
The 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 and all Chrysler 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. see scheme 1
DIVERTER VALVE
The air flows from the air pump into the diverter valve. This valve prevents backfiring, by stopping air injection flow during periods of high increase in manifold vacuum (such as during deceleration). The diverter valve dumps the air supply to the atmosphere for the first few seconds of deceleration.
Most diverter valves also have a built-in pressure relief valve, which bleeds off excessive air pump pressure to prevent damage to the system. Most diverter valves are similar. (Scheme 73)
Diverter Valve (Typical) Spring pressure holds valve open; air flows to exhaust. Scheme 73
INJECTION MANIFOLD
The injection manifold in many applications is an external tubing system, mounted to the 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 an internal air injection system, consisting of specially drilled passages in the intake manifold, which carry the air pump air to the exhaust ports. External tubing is eliminated.
CHECK VALVE
The check valve is a 1-way flow valve. It prevents exhaust manifold air from backing up through the system and reaching the air pump. The check valve will be found either in the tubing, leading to the injection manifold or as an integral part of the 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 the pulley and pulley bolts. Do not attempt to hammer or press filter on shaft.
Removing Centrifugal Fan Filter from Pump w/Pulley Removed Be careful that fragments do not enter air intake hole. Scheme 74
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. However, certain service items can be replaced as follows
PUMP EXHAUST TUBE REPLACEMENT
Remove by placing tube in a vise, or use pliers to pull tube with a twisting motion. Insert new tube into hole, and tap in using a block of wood to protect tube. Approximately 7/8" (22 mm) of tube should extend above cover.
DIVERTER VALVE TEST
Check valve by accelerating engine, and allowing throttle to close rapidly. A 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.
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 the Air Injection System is dependent upon proper engine tune-up. See individual vehicle models for specifications and procedures.