Backfiring after re-installing smog pump

[notrod59]

They changed the emission laws where I live, so I had to put the smog pump back on my 81 Blazer. I finally got it going, after 5 trips to NAPA to get the right belt, but now it's backfiring when I take my foot off the gas pedal. To my knowledge the only thing the smog pump does is inject air into the headers and dilute the exhaust (giving the illusion of cleaner emissions). I'm not sure why this would make a difference. I didn't mess with the timing or carb mixture or do I need to? I think I had the same problem 10+ years ago when I had to have emissions but I can't remember. Any suggestions?

[1LowToy]

There is a vacuum port on the valve on the air pump. It needs manifold vacuum, or if it does have it the valve is bad. Getter fixed or it will blow the muffler apart.

[notrod59]

Thanks. The vacuum connection was broken off so I didn't see it. I did a little modification to it but it still backfires.
I have another valve here but it has bigger ports so my hoses won't fit. I'll have to find something to adapt them and give the other one a shot before I go buy one.

[Dan1969]

You will get some really bad Back fire if there's also a gap on the exhaust where it connects with the exhaust manifold.

[notrod59]

WOWThis is weird! I still have the same problem almost 5 years later. The Blazer's been broke down for most of that time for other reasons. I found a valve on craigslist and did a search to make sure it was the part I needed.
This was the second result in the search list!
Gonna buy that valve finally!

[notrod59]

Awe sh*T! Not gonna buy that one. The guy says it doesn't work and is selling it for "appearances"... Thought I had a deal for $30.