OldS10

Does anyone out there understand how the air injection system is designed to run?
The air pump will sometimes run for a number of seconds and stop. I only notice this while at a stop light and idling. I am guessing that the system is "self testing" , but not sure. The other thing that it sometimes does, is to repeatedly start the pump, stop, start again, and stop again numerous times, maybe 20 or so times. When it does this, it only runs for a second each time, like you hit a momentary switch repeatedly. I runs for so short a time, that the pump doesn't come up to speed. We set the PCM to ignore the self test results, as we relocated the air injection point from the exhaust manifold to the exhaust pipes, in front of the cats and the self test would fail, since the front O2 sensors would not see the burst of fresh air. As the vehicle has to meet the standards of a 98 Vette, we left the emissions as intact as we could. I am guessing that the start & stop that the air pump is doing isn't normal, but hope someone out there knows a lot more than I do.
Your help is appreciated! Thanks

V-seriesTech

iTrader: (5)

my generic busy answer:

Cut and paste

rom All Data:

PURPOSE
The Secondary Air Injection (AIR) system helps reduce Hydrocarbon (HC), Carbon Monoxide (CO), and Oxides of Nitrogen (NOx) exhaust emissions. It also heats up the warm up 3-way catalytic conventers quickly on engine start-up so conversion of exhaust gases can occur sooner.

SYSTEM COMPONENTS
AIR Pump
The AIR pump is mounted to the lower left front of the engine Compartment and supplies the air to the AIR system. The electric air pump pressurizes air from the engine and pumps it to the check valves near the exhaust manifolds. The AIR pump is controlled by the PCM. Battery voltage to the AIR pump is controlled by the AIR pump relay. An integral stop valve prevents air flow through the pump during OFF periods. When the PCM provides a ground circuit for the secondary AIR pump relay, battery voltage is allowed to power up the AIR pump and integral stop valve.

Vacuum Bleed Valve
This valve helps prevent vacuum buildup within the AIR system, which could prevent the integral stop valve from opening. The bleed valve is controlled by the air pump relay and will be energized when the AIR pump is commanded ON. If the vacuum relief system is not functioning, the vacuum will cause the AIR pump integral valve not to open. This may result in no AIR flow to the exhaust manifolds or delay the delivery of air which may not allow the diagnostic to pass.

Check Valves
Check valves - The check valves prevent back flow of exhaust gases into the AIR pump in the event of an exhaust backfire.

Necessary plumbing

* Hoses
* Pipes
* Clamps

OPERATION
AIR Pump Control
The AIR pump with integral stop valve is controlled by the PCM. The PCM will turn ON the AIR pump by providing the ground to complete the circuit which energizes the AIR pump relay. When air to the exhaust ports is desired, the PCM will turn ON the integral stop valve and then the AIR pump.

The PCM turns ON the AIR pump during startup any time engine coolant temperature is above -10°C (14°F). The AIR pump will operate for a maximum of 240 seconds, or until the system enters Closed Loop operation. At the same time the PCM turns the AIR pump OFF, it also de-energizes the integral stop valve solenoid so no air is directed to the exhaust ports.

SYSTEM DISABLE CONDITIONS
The AIR system will be disabled under the following conditions:

* When the PCM recognizes a problem and sets a diagnostic trouble code.
* When the fuel system is operating in Closed Loop.
* The AIR pump has been ON for 240 seconds.
* Engine Speed is greater than 2825 RPM.
* Manifold Absolute Pressure (MAP) is greater than 96 kPa (14 psi) with Vehicle Speed Sensor (VSS) over 60 mph.
* MAP is less than 20 kPa (3 psi).
* Engine Coolant Temperature (ECT) less than -10°C (14°F).
* Warm up 3-way catalytic converters over temperature detected.
* Short and long term fuel trim are not in their normal ranges.
* Power enrichment is detected.

RESULTS OF INCORRECT OPERATION
No Air Flow
If no air (oxygen) flow enters the exhaust stream at the exhaust ports, HC and CO emission levels will be too high.

Constant Air Supply
Air flowing to the exhaust ports at all times could increase temperature of the warm up 3-way catalytic converter.

DIAGNOSTIC TROUBLE CODES
Diagnostic Trouble Codes P0410, P0412, P1415, and P1416 will set if there is a malfunction in the following components:

* The AIR pump.
* The AIR pump relay.
* Hoses or pipes that are leaking.
* The Check valves that are leaking.
* Circuits going to the AIR pump and the AIR pump relay.
* The vacuum bleed valve.

OldS10

Thanks for the info.....

I cannot find a vacuum relief valve or the wiring or connector. True, we integrated the engine into another vehicle, but the engine harness was kept intact and I do not remember seeing an electric valve on the AIR injection plumbing removed from the Vette. I also went down to the local GM dealer and had the parts guys look up the vacuum relief valve.....nothing. In looking at the diagrams in the 98 Corvette GM shop manuals (the big 3 volume set) I see nothing for a vacuum relief valve. No remove & replace instructions. The only mention of the vacuum relief valve that I can find is in the system description and in what you replied with.

Any ideas?

Thanks again.