See Figures 1 and 2
Some 240 Z and 260 Z models are equipped with a positive displacement air pump to inject fresh air into the exhaust ports to accelerate combustion in the manifold. The system includes:
- An anti-backfire valve. When the throttle is suddenly closed, this valve diverts the air pump discharge into the intake manifold in order to promote burning in the combustion chambers and minimize burning in the exhaust manifold.
- A check valve. This device prevents exhaust gases from traveling back into the air pump when exhaust pressure exceeds air pump discharge pressure.
- An air pump relief valve. This valve controls the air pump discharge pressure in order to protect the pump from excessive pressure.
- Operate the engine until it reaches normal operating temperature.
- Inspect the hoses and connections, replace any damaged hoses or clamps and retighten any connections as needed.
- Check the air pump belt tension and adjust, as necessary.
- Disconnect the air supply hose from the check valve.
- Insert the open end of an air pump test gauge into the air supply hose and clamp it securely. This adapter is required because it provides a relief port of critical size.
- Operate the engine at 1,500 rpm and read the test gauge. The pressure should be 0.30 psi (0.63 in. Hg) or more.
- With the engine still at 1,500 rpm, close the relief port in the gauge adapter and listen for leaks. If there is any leakage from the relief valve, it is faulty.
- If the system fails the pressure test, the pump must be replaced unless the problem is in the relief valve.
- Stop the engine. Inspect the check valve plate position. The plate should be in light contact with the seat away from the air manifold.
- Insert a small screwdriver into the valve connection, depress the valve plate and release it. It should return to the seat freely.
- Start the engine and slowly bring the idle speed up to 1,500 rpm. There should be no leakage of exhaust gas from the check valve although a slight fluttering at idle is normal.
- If the check valve fails any of the tests, replace it.
- Reconnect the air supply hose and remove the air cleaner cover.
- Lightly position a finger over the inlet hole for the anti-backfire valve. DO NOT shut the hole off entirely.
- Increase the engine speed to 3,000-3,500 rpm, then suddenly release the linkage. There should be a sudden flow of air during deceleration. If there is no outflow or if outflow exists under other than deceleration conditions, replace the valve.
REMOVAL & INSTALLATION
- Disconnect the hoses from the housing.
- Remove the bolt used to position the pump on the belt adjusting bar. Remove the pump-to-mounting bracket bolts.
- Remove the drive belt and the pump.
- To install the pump, reverse the removal procedures. Adjust the drive belt tension.
See Figure 3
No special instructions are required except that the valve must be replaced with its diaphragm chamber upward. Never attempt to disassemble and repair the valve.
- Disconnect the air supply hose.
- While removing the valve, put opposing pressure on the flange of the air manifold with a wrench.
- To install, reverse the removal procedures, again using pressure in opposing pressure to install the valve on the air manifold flange. Never attempt to disassemble and repair the valve.