The exhaust emission air injection system consists of a belt driven air pump which directs compressed air through connecting hoses to a steel distribution manifold into stainless steel injection tubes in the exhaust port adjacent to each exhaust valve. The air, with its normal oxygen content, reacts with the hot, but incompletely burned exhaust gases and permits further combustion in the exhaust port or manifold.
See Figures 1, 2 and 3
The air injection pump is a positive displacement vane type which is permanently lubricated and requires little periodic maintenance. The only serviceable parts on the air pump are the filter, exhaust tube, and relief valve. The relief valve relieves the air flow when the pump pressure reaches a preset level. This occurs at high engine rpm. This serves to prevent damage to the pump and to limit maximum exhaust manifold temperatures.
Pump Air Filter
The air filter attached to the pump is a replaceable element type. The filter should be replaced every 12,000 miles under normal conditions and sooner under off-road use. Some models draw their air supply through the carburetor air filter.
Air Delivery Manifold
See Figure 4
The air delivery manifold distributes the air from the pump to each of the air delivery tubes in a uniform manner. A check valve is integral with the air delivery manifold. Its function is to prevent the reverse flow of exhaust gases to the pump should the pump fail. This reverse flow would damage the air pump and connecting hose.
Air Injection Tubes
The air injection tubes are inserted into the exhaust ports. The tubes project into the exhaust ports, directing air into the vicinity of the exhaust valve.
The anti-backfire diverter valve prevents engine backfire by briefly interrupting the air being injected into the exhaust manifold during periods of deceleration or rapid throttle closure. The valve opens when a sudden increase in manifold vacuum overcomes the diaphragm spring tension. With the valve in the open position, the air flow from the air pump is directed to the atmosphere.
On the 1972 6-232 engine, the anti-backfire valve is what is commonly called a gulp valve. During rapid deceleration the valve is opened by the sudden high vacuum condition in the intake manifold and gulps air into the intake manifold.
Both of these valves prevent backfiring in the exhaust manifold. Both valves also prevent an over right fuel mixture from being burned in the exhaust manifold, which would cause backfiring and possible damage to the engine.
REMOVAL & INSTALLATION
- Loosen the bolts on the pump pulley.
- Loosen the air pump attachment racket. On V8 models with air conditioning, loosen the power steering pump to aid in drive belt removal.
- Detach the air supply hoses at the pump.
- Remove the drivebelt and pulley from the hub.
- Unfasten the bolts on the bracket and remove the pump.
- Place the pump on its mounting bracket and install, but so not tighten the attachment volts.
- With the rotor shaft used as a center, fit the pulley into the hub and install the drive belt over the pulley.
- Tighten the pulley attachment bolts, using care not to snap them off.
- Adjust the pump until the belt is secure. Tighten the mounting bolts and the adjusting screw to 18-22 ft. lbs. Do not overtighten.
- Attach the hoses and clamps.
Air Pump Relief Valve
- Use a gear pulley and a steel bridge to remove the relief valve from the pump.
- Remove the pressure plug from the new relief valve assembly.
- Insert the relief valve into it housing mounting hole.
- Place a block of wood over the valve. Use a hammer to tap the valve until it lightly registers against the housing. Use care not to distort the housing.
- Press the pressure plug into the center of the relief valve.
Centrifugal Filter Fan
Never attempt to clean the filter fan. It is impossible to remove the fan without destroying it.
- Remove the air pump from the car, as detailed above.
- Gently pry the outer disc off and pull off the remaining portion. Be careful that no fragments from the fan enter the pump air intake.
- Install a new filter fan pulling it into place with the pump pulley and attaching bolts.
- Alternately tighten the bolts so that the fan is drawn down evenly. Be sure that the outer edge of the fan fits into the pump housing.
- Install the pump on the car.
For the first 20-30 minutes of operation, the fan may squeal until its lip has worn in. This is normal and does not indicate a damaged pump.
- Remove the exhaust tube by grasping it (never the pump body) in a vise or a pair of pliers. Pull the tube out with a gentle twisting motion.
- Install the new exhaust tube by tapping it into the hole with a hammer and a wooden block. Be careful not to damage its end.
- Tap it until 7 / 8 in. (22.23mm) of the tube remains above the pump cover.
Do not clamp the pump in a vise while installing the exhaust tube.
By-Pass (Diverter Valve)
- Disconnect the hoses from the valve.
- Remove the screws that attach the valve bracket to the engine. Remove the valve and bracket assembly.
- Installation is the reverse of removal.
Air Injection Manifold and Check Valve Assembly6-232 AND 258 ENGINES
- Remove the intake/exhaust manifold assembly, after disconnecting the hoses from the air injection manifold.
- Place the assembly in a vise and unfasten the retaining nuts on the air injection manifold at each cylinder exhaust port.
- Lightly tap the injection tubes, then pull the injection manifold away from the exhaust manifold.
- If the tubes have become fused to the injection manifold, remove them by applying heat while rotating them with pliers.
- Insert new air injection tubes into the exhaust manifold.
The shorter tubes of into the Nos. 3 and 4 cylinders.
- Using a new gasket, assemble the exhaust/intake manifold to the engine.
- Using new gaskets, install the air injection manifold on to the exhaust manifold in the reverse order of removal.
- Detach the air delivery hose at the check valve.
- Unfasten the air injection manifold attachment nuts from the cylinder head. Carefully, ease the air injection manifold away from the heat.
On some models it may be necessary to lower the bottom steering shaft clamp to gain access to the left rear mounting bolt; or to disconnect the right engine support and raise the engine to remove the right air injection manifold assembly.
- On newer cars, the air injection tubes and the manifold are removed as an assembly.
- On older models, or if the tubes are hard to remove, use a screw extractor to twist the tube out gradually.
Some interference may be encountered because of the normal carbon buildup on the tubes. Injection tubes which are removed with a screw extractor must be replaced with new ones.
- Installation is the reverse of removal.
- Check the pump drive belt tension. There should be about 1 / 2 in. (12.7mm) play in the longest span of belt between pulleys.
- Turn the pump by hand. If it has seized, the belt will slip, producing noise. Disregard any chirping, squealing, or rolling sounds from inside the pump; these are normal when it is turned by hand.
- Check the hoses and connections for leaks. Hissing or a blast of air is indicative of a leak. Soapy water, applied lightly around the area in question, is a good method for detecting leaks.
- Disconnect the air supply hose at the antibackfire valve.
- Connect a vacuum pressure gauge to the air supply hose.
If there are two hoses plug the second one.
- With the engine at normal operating temperature, increase the idle speed and watch the gauge.