To my understand the air pump engages at idle for emmisions. What rpm range is "idle"(800 to 600rpm)? Does the air pump engange only when the pcm is in open/closed loop? Are there any other variables that come into play for the pcm to send the signal to the air pump relay?
Thank You

 

Been awhile since I played with one since there is a TSB on the b-bodies allowing the AIR system to be legally defeated by the dealership, but...................
From memory the AIR comes into play mostly at cold start and WOT. Open loop only because introduction of fresh air to the exhaust pre-O2s during closed loop would confuse the hell out of the system.

 

No. The pump is electric. It turns on when you start the engine, and runs for about 3 minutes. It's sole pupose is to burn the excess fuel in the richened cold start mixture, to help the cat(s) heat up faster. Once the timer times out, it won't run again. Its not like the AIR pump used in the 3rd Gens. That pump ran continuously (belt driven) and switched the air flow from the manifolds (where it was routed on cold start) to the AIR connection on the cat, to supply extra air for the oxidation reaction required to oxidize the CO to CO2 and the unburned HC's to CO2 and water.

 

The PCM turns on the AIR pump after startup when engine temp is above 59°. It will operate for a maximum of 240 seconds or until the system goes into closed loop. It will go off if RPM exceeds 2825 (or obviously, WOT). There are some other MAP parameters that will also cause it to shut off.

 

Do not use a test light unless you have one(with diodes) specifically designed to test low current circuitry

The vehicle is a 94 camaro, I believe the air pump is still required here in california for this vehicle. The reason I ask this question is because everthing on the system "seems" to be working proprely except one thing. The neg signal from the pcm going to the relay in the engine compartment is testing to be a good ground when vehicle is on, however when I put a test light on it with a good positve it will not test good. Seems like whenever I put a load on the ground (even the relay) it does not work? I think its a bad wire so I'm going to test this by putting in a temporary "direct" line to the relay to see what happens. Does this seem like a reasonable test? If nothing I'll check on thoes MAP parameters.

 

I decided not to put the temporary line in, the equipment is in, resistance on wire from PCM to relay is good, not throwing any codes, I'll revisit this if I have an issues during the smog inspection. I don't think I was running the tests during open loop and within the 240 second time frame.

 

The AIR pump is required on all F-Bodys in all states. The recall, and authorized deletion of the AIR pump was for the B-Bodys (Caprice/SS/Roadmaster/etc.) only.

Normally, the emissions tests only check the engine at normal operating temperature, not from a cold start, so the operation of the AIR pump is not going to affect emissions during the test. All they can do is a visual check to make sure its still there and connected.

You never really stated what the problem is you are trying to fix????? Does the pump not run on startup? That's the only time it is required. You also have to make the check within the first 205 seconds, since that's when the PCM open loop timer runs out, and the PCM will start to operate in closed loop, without the pump. If, for some reason your O2 sensors did not display the required activity at 205 seconds, and the coolant temp did not exceed the threshhold for closed loop operation, the AIR pump would continure to operate for another 35 seconds, but it is extremely unusual for the event to require more than 205 seconds from startup.

 

Yes, the problem is the air pump not turning on. I tested (with voltmeter at relay) the neg lead from the pcm during vehicle run and received a good ground. However, when I put any sort of load on the ground (the relay, a test light) the ground would not hold.

I can manually jumper at the relay location to turn the air pump on, and the relay its self is good.

The vehicle does enter closed loop.

 

I tested the air pump during open loop and it does run for about the 240 secs. It's kind of strange that even when the pcm is not sending the "ground" to the air pump relay, the line from the pcm still tests as ground with a voltmeter.

Thanks for the clarification guys

 

If I am understanding you correctly kyleg001 you are wondering why your test light wont light up when you are connecting it to a good positive and the relay trigger wire (-) coming from the pcm? The current supplied is only meant to close a relay(~500 milliamps), not nearly enough to light your test light, and furthermore, you shouldn't connect your test light to your pcm leads because you are potentially sending 12v (+) directly in to the pcm signal wire (the light filament in the bulb acts as a jumper wire to an extent). I have always been taught never to test your cars computer components with a test light. A multimeter is fine however because they have huge amounts of internal resistance so they will not harm computer components.

Hope this helps

-Jerry

 

Jerry,

Thanks for your reply.

You are correct, it's probably not a good idea to use a test light. I don't believe many of them include the internal circuitry that mine does.