Air pump?

[R422b]

Haha ok. I'll have to do some research to learn more about this and see if I can maybe route my belt to avoid the air pump to get a little more gas mileage. Because using less gas helps the environment too, right!? And I don't have cats anyway [emoji2375]

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Chuck it off the highest cliff you have available. [emoji16]

Talking about GMT400s using Tapatalk

 

[Erik the Awful]

In your first picture, the lower-left-most, gray component is your air pump.

The air pump draws almost no horsepower. If it works, leave it. If you upgrade to newer cats, feel free to delete it, but understand that you're technically in violation of federal law. My truck had no cats nor air pump when I got it, and I put newer cats on it, but I'm still technically in violation of the law even though I'm trying to do the right thing.

 

[PlayingWithTBI]

I'm not sure if the TBI trucks were 2 way or 3 way catalysts. 3 way would make more sense, but they were the older pellet style in 88.

Yeah, they were 2-way and quite restrictive. That's why they came up with the EGR valve to reduce NOx. A newer 3-way will help do that.

 

[Schurkey]

You must be registered for see images attach

1. It's not an "air pump". It's an A. I. R. pump, Air Injection Reaction. GM does love it's acronyms, although I generally leave out the periods and spaces. The name gives a clue to it's purpose--supporting a chemical reaction by adding air to the exhaust stream.

2. "Diluting" the exhaust with ordinary air is not it's purpose.

3. AIR pumps were on vehicles years before catalytic converters. The intention of the thing depends on the overall emissions-reduction strategy.

The purpose of AIR on my '88 K1500 is to warm-up the exhaust system, in particular the catalyst, immediately after engine start. Catalytic converters don't work when they're cold. The oxygen sensor doesn't work when it's cold. The rich mixture provided by the cold-enrichment system means the exhaust gas is not fully-reduced. In other words, the exhaust gas is capable of supporting combustion even after it's being blown down the exhaust port--all it needs is additional oxygen squirted-into the exhaust manifold to turn carbon monoxide (CO) to carbon dioxide (CO2); and if there's still hydrocarbons (HC) in the exhaust, they'll reduce to water vapor (H2O) and CO2. In the process, that combustion produces additional heat that warms everything down-stream.

The AIR system shouldn't pump air into the manifold once the computer is ready for closed-loop operation--the additional oxygen from the air being pumped into the exhaust manifold will screw-up the O2 sensor readings. So the output of the AIR pump is diverted into the air cleaner. But by then, the exhaust system is warm enough that the catalyst is functional.

Other uses of the AIR pump involve "full time" reduction of combustible exhaust, exactly as described above. In vehicles that don't have O2 sensors, (My high-school '69 Chevelle, for example) the air was blown into the exhaust manifold almost the whole time the engine was running. There was a vacuum-sensing diverter valve that stopped air flow into the exhaust system during deceleration(high manifold vacuum.) Air in the exhaust during deceleration leads to exhaust backfires that blow the muffler apart. I had two blown mufflers on my Chevelle for this exact reason.

A third use of the AIR pump/diverter valve involves "upstream/downstream" switching. "Upstream" air warms the exhaust system as before, getting the catalyst and O2 sensor (if used) toasty, quickly. Then the system would switch to "downstream" injection, into the catalyst itself to provide oxygen for the reaction within the cat converter. Downstream injection was always far behind the O2 sensor, (if used) so it didn't screw up the signal. Typically, the air was blown into the catalyst behind the first section but ahead of the second section. The first section reduced hydrocarbons and CO, the second section worked on oxides of nitrogen (NOx)

The AIR pump (in good condition) doesn't use enough horsepower to make a difference. You'll never see it on the fuel economy without real instrumentation. They can go bad, bearings seized, etc. so they become hard-to-turn, noisy, etc.

The diverter valves tend to cause more problems--sticking in one position instead of switching back-and-forth like they're supposed to. Exhaust backfires result from sticking one way, if it sticks the other way on an '88, you'll just have slower exhaust warm-up.

In general, the system is simple and reliable. No reason to disable it, or to be scared of it. If it's broken, it's easy to fix.

 

[RANDALL COOK]

A worn belt can cause squeaking. Other things can cause a good belt to squeak, including the A/C if it is overcharged, or has a bad bearing; the air pump can also start dragging (if you have one). If the belt has cracks, especially between the ribs, replace it. Also, check for a weak idler pulley spring. When is it squeaking? At start up, turning on A/C, when driving through puddles, turning a corner, all the time, etc.

 

[kenh]

The old saying goes...."The solution to pollution is dilution". MY opinion was the air pump just diluted the exhaust so it could meet the numbers. Ya it may have made some other minor differences?????

Ken

 

[Supercharged111]

The old saying goes...."The solution to pollution is dilution". MY opinion was the air pump just diluted the exhaust so it could meet the numbers. Ya it may have made some other minor differences?????

Ken

You'd need a helluva lot bigger air pump to appreciably dilute the emissions in the exhaust.

 

[Kat141]

You must be registered for see images attach

1. It's not an "air pump". It's an A. I. R. pump, Air Injection Reaction. GM does love it's acronyms, although I generally leave out the periods and spaces. The name gives a clue to it's purpose--supporting a chemical reaction by adding air to the exhaust stream.

2. "Diluting" the exhaust with ordinary air is not it's purpose.

3. AIR pumps were on vehicles years before catalytic converters. The intention of the thing depends on the overall emissions-reduction strategy.

The purpose of AIR on my '88 K1500 is to warm-up the exhaust system, in particular the catalyst, immediately after engine start. Catalytic converters don't work when they're cold. The oxygen sensor doesn't work when it's cold. The rich mixture provided by the cold-enrichment system means the exhaust gas is not fully-reduced. In other words, the exhaust gas is capable of supporting combustion even after it's being blown down the exhaust port--all it needs is additional oxygen squirted-into the exhaust manifold to turn carbon monoxide (CO) to carbon dioxide (CO2); and if there's still hydrocarbons (HC) in the exhaust, they'll reduce to water vapor (H2O) and CO2. In the process, that combustion produces additional heat that warms everything down-stream.

The AIR system shouldn't pump air into the manifold once the computer is ready for closed-loop operation--the additional oxygen from the air being pumped into the exhaust manifold will screw-up the O2 sensor readings. So the output of the AIR pump is diverted into the air cleaner. But by then, the exhaust system is warm enough that the catalyst is functional.

Other uses of the AIR pump involve "full time" reduction of combustible exhaust, exactly as described above. In vehicles that don't have O2 sensors, (My high-school '69 Chevelle, for example) the air was blown into the exhaust manifold almost the whole time the engine was running. There was a vacuum-sensing diverter valve that stopped air flow into the exhaust system during deceleration(high manifold vacuum.) Air in the exhaust during deceleration leads to exhaust backfires that blow the muffler apart. I had two blown mufflers on my Chevelle for this exact reason.

A third use of the AIR pump/diverter valve involves "upstream/downstream" switching. "Upstream" air warms the exhaust system as before, getting the catalyst and O2 sensor (if used) toasty, quickly. Then the system would switch to "downstream" injection, into the catalyst itself to provide oxygen for the reaction within the cat converter. Downstream injection was always far behind the O2 sensor, (if used) so it didn't screw up the signal. Typically, the air was blown into the catalyst behind the first section but ahead of the second section. The first section reduced hydrocarbons and CO, the second section worked on oxides of nitrogen (NOx)

The AIR pump (in good condition) doesn't use enough horsepower to make a difference. You'll never see it on the fuel economy without real instrumentation. They can go bad, bearings seized, etc. so they become hard-to-turn, noisy, etc.

The diverter valves tend to cause more problems--sticking in one position instead of switching back-and-forth like they're supposed to. Exhaust backfires result from sticking one way, if it sticks the other way on an '88, you'll just have slower exhaust warm-up.

In general, the system is simple and reliable. No reason to disable it, or to be scared of it. If it's broken, it's easy to fix.

Schurkey, would you know where to get a replacement smog/a.i.r. pump for an '88 K3500 with TBI, 4x4?

 

[Schurkey]

Treasure Yard would be my first choice.

There may be "rebuilts" or even new pumps offered by the local parts store, or via internet/mail-order.

 

[Majoraslayer]

I'm curious what trucks even had them. I've always wondered what the empty spot was on my accessory bracket, and of the several junk yard trucks I've pulled parts from I'd never seen one of these pumps in person. The only place I've ever seen one was online pics of engine bays, and this thread is actually where I learned how it even works. The closest I've come to encountering one in the wild was picking up a used set of OEM exhaust manifolds that had chopped off metal lines plumbed into them for it. I thought maybe it was just the early trucks that got them for emissions and the need was eliminated later, but the later style aluminum bracketry has provisions for it too. My own truck is a 1988 and didn't have it from the factory. Is it maybe a 2500+ feature?