The truck is an '87 with the 22R. Decided to do alittle checking around today under the air cleaner. Came across this thing? Notice how it's unplugged? See the vacuum line in the other picture with the screw stuck in it? This is something that the previous owner apparently bypassed.

Out of curiosity, I hooked it up. When I start the truck, it idles like crap.....and blows black smoke from the tailpipe. When I disconnect it again, the truck runs fine again. I'm guessing this little diaphram thingy isn't doing its job correctly? <img src="/forums/images/graemlins/lol.gif" alt="" /> My question is. What it is? What is it supposed to do?

Any chance on larger pictures? Can't see crap on those small ones..

From the symptoms you describe, sounds like a bad AAP (auxillary accelerator pump). Easy little fix.. I presume you can get a new once for a few bucks from your parts store. Comes with the 40 dollar rebuild kit from NAPA.

The AAP is on the lower front drivers side corner of the carb.. I assume this is what is unhooked. Won't hurt any unplugged. My understanding is the AAP gives you some more gas when cold (right Josh?).

-Scerb

Edit: AHA! I post and I get larger pictures instantly <img src="/forums/images/graemlins/lol.gif" alt="" /> Yep, that sure is the AAP!

Hmmm upon further examination of the new big pictures, I see this:



I THINK that is the Choke Breaker. It seems as it is unplugged and although it looks like its plugged in in the pic, the line I highlighted is probably leading to no where. Double check and see if I am correct. Again, doesn't hurt to be unplugged. I think the CB 'vacumatically' breaks the choke <img src="/forums/images/graemlins/lol.gif" alt="" />... Also looks like the diaphram is plugged with shiny gold solder.. dunno what to say about that (again Josh? - Josh is carb god <img src="/forums/images/graemlins/cyclops.gif" alt="" />)

If two out of your three diaphrams aren't functioning, its probably time for a rebuild.

-Scerb

that's the AAP. when it fails, it leaks fuel.

See this post for info on what it is.

http://www.4x4wire.com/forums/showf...;oldertype=&bodyprev=#Post716189