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trymes
03-04-2020, 02:57 AM
So, I have found myself in the possession of a Skylark coupe, and it is running like a bag of ____ from what seems like too much fuel. Although I know that 90% of carburetor problems can be traced back to the ignition system, I did take the carb air horn off and the fuel bowl seems to have more than its fair share of rusty grit in there. I was planning on throwing a carb kit at it because ... well, why not? Maybe the grit was preventing needle from seating properly?

Having said that, the previous owner also removed the air pump, which seems like a bad idea to me. Can anyone speak to whether I should reinstall the air pump, leave it off, or perhaps source a rebuilt one?

Many thanks,

Tom

PS: I?m bound to be asking 10,000 other questions going forward, so please be patient!

Pontiac6ksteawd
03-04-2020, 04:57 PM
Welcome to the forums trymes. Im not sure which year Skylark you have, it could be an X-body (rear drive), it could be X-body (front drive), it could be A-Body (rear drive), or it could be A-body (front drive). Please let us know, it would help further, and which engine you have. A pic would also help leaps and bounds.

The air pump just pumps in fresh air to help the catalyst system. Is it needed? Only if your state has emissions. I removed it, and the system on every car I have ever had with it. Its just a big pain in the ass.

Beyond that, I cant help much. I have only owned a couple Carb cars, and I will never own one again, LOL. And the ones I did have, I never worked on the carb.

trymes
03-04-2020, 06:31 PM
Whoops. I didn?t specify the year because this is the X-body forum. It?s an ?84 Skylark FWD X-body car. 2.8 V6 with a E2SE CCC carb.

My suspicion with the air pump was that the computer is relying on that to be doing its job and its absence could possibly cause it to mis-adjust the mixture some.

Pontiac6ksteawd
03-04-2020, 07:03 PM
I would likely say that carb just needs a rebuild.

They were not a well built carb.

CorvairGeek
03-04-2020, 11:39 PM
I would likely say that carb just needs a rebuild.

They were not a well built carb.

You aren't kidding there!

Just as an FYI, air injection to the exhaust manifold is not active by design when the system is closed loop, i.e. monitoring the exhaust stream via the O2 sensor (at least back in this era GM). With that said, a system with a diverter valve problem will wreak havoc with fuel control if a system is injecting at the manifold when it shouldn't be (i.e. forcing a very rich condition).

trymes
03-05-2020, 02:56 AM
Jerry: are you saying that a bad diverter valve will force air into the exhaust when it shouldn?t, causing the O2 sensor to see a lean condition, and causing the ECU to enrich the mixture? Is there a good way to test this out?

CorvairGeek
03-05-2020, 11:57 AM
Jerry: are you saying that a bad diverter valve will force air into the exhaust when it shouldn?t, causing the O2 sensor to see a lean condition, and causing the ECU to enrich the mixture? Is there a good way to test this out?

That is correct, but only if the air injection pump is present and operating. Not a problem if the pump is missing.

The factory service manual has excellent descriptions of how the system operates. It pumps to the exhaust manifold(s) on cold start, then primarily switches to divert or the catalytic converter for most of normal operation. The timing and exact operation varies between engines and model years.

trymes
03-05-2020, 12:42 PM
That is correct, but only if the air injection pump is present and operating. Not a problem if the pump is missing.

Thank you. I should have added that bit. My plan is to try and get this beast running well before worrying about adding the air pump back. BTWm if the PO failed to properly cap the line from the air pump, would that be causing any issues. Sounds to me that the check valve should prevent any exhaust from flowing backwards, and with no air being introduced, it wouldn't do anything.

I'm trying to located a good scanner right now, so I can see the duty cycle of the solenoid, TPS voltage, etc. The Actron 9690 is available new, comes with the cable, but it is about $250.00, while I might be able to pick up a SnapOn MT2500 locally, which is old, but presumably available for less.

Tom

CorvairGeek
03-05-2020, 01:34 PM
An open check valve can introduce some air, but it usually isn't a big deal. A 1/2 inch metal cap can at least block it and stop the small amount of noise too, without the bigger job of trying to remove the smaller ports at the manifold.