Secondary air injector pump / check valve

[c bausch]

Hey been search around and I'm kinda confused on what to do. I have a bad pump or check valve and here is my findings,

I pulled the black 1" hose off of the check valve and started the truck and it blew air out now that means the pump is good?

Later in the evening i started the truck ran to the front and put my hand on the check valve while it does its cycle it did and i heard and felt a thunk after it was done so im assuming that its working

But when everything is hooked back up i hear the jet sound for about 10 seconds then shuts off soooo.... Whats going on here?

 

[The_Roadie]

...I have a bad pump or check valve ...

You may be jumping to a diagnosis without knowing exactly what the system diagnostic is looking for.

Do you have a CEL code? What is it? How many miles? When did you last change the plugs and upstream O2 sensor?

The turbine sound, hose blow, and check valve noise is as expected. You should pull the hose and have somebody else start the engine and make sure you can hear exhaust noises coming out of the check valve for those first few seconds. That makes sure it's opening all the way and not just a partial. You may have a sticky check valve.

But the SAIS diagnostic also depends on a well-running O2 sensor, which I explained a few times on the OS but maybe I've never repeated that essay over here.

 

[c bausch]

No codes ever came up , been 2 years when this first started happening

59k on the dash as we speak its a 2007

I did the plugs at 30k and probably going to change them again at 60k miles

Never changed the o2 sensors (no ses)

Every early morning i start it but the truck sounds like crap like a slightly caned out race car while is cycles then it stops and eveyyhing is normal

 

[The_Roadie]

No codes? Why suspect the SAIS then?

 

[c bausch]

Because of the jet like sound for about sec on start ups

Unless you recommend me looking at something else

 

[The_Roadie]

It's supposed to sound like a shop vac for 10-20 seconds on cold starts. It's a very powerful turbine pump. It injects fresh air into the exhaust manifold to encourage burning of the initially rich mixture the PCM delivers at start-up. It's supposed to hasten the PCMs entry into the reduced-emissions closed loop mode. All it does is reduce emissions on start-up and allow GM to meet the EPA's requirements that changed after the 2002 model year.

Listen to another truck with the SAIS and compare them. The system has a lot of things that go wrong if you aren't hearing the pump, but they all result in a code.

Could you be hearing the cooling fan noise, which is also normal for a few seconds if the clutch drains some of its silicone fluid overnight?

Do you have any other symptoms besides a noise? You could have a functional pump with a deteriorating bearing or impeller that's making extra noise. Again, find a buddy and compare it to theirs.

 

[c bausch]

I just hear the hi pitched sound with crappy exhaust putting then it goes away after it cycles trough

 

[BRomanJr]

No codes ever came up , been 2 years when this first started happening

59k on the dash as we speak its a 2007

I did the plugs at 30k and probably going to change them again at 60k miles

Never changed the o2 sensors (no ses)

Every early morning i start it but the truck sounds like crap like a slightly caned out race car while is cycles then it stops and eveyyhing is normal

If you use the correct Delco Iridium plugs they will go 80-100k miles (mine went 160k). O2 sensors get lazy before they throw a code, schedule it for your 100k service.

You might have an SAIS hose that is leaking.