Posted this at the V6 board already but I hope it's ok to post here too:

My son and I have been troubleshooting a carb problem on his '82 Camaro 2.8L for several weeks. We have tried 2 rebuilt carbs because the engine is running too rich (no power; black smoke; backfire through carb; gas evident in intake manifold) but neither did any good. New intake (carb) gasket has been installed, all vacuum lines are good. As far as we can tell the choke is working-linkage and moving parts all moving freely. +14vdc going to the choke heater coil but I don't know if that's right or not.

What's baffling is that sometimes (not very often) the car will run perfect-no hesitation, no black smoke, idles as smooth as a new car! But most of the time when you start it you have to push the throttle practically to the floor to keep it running and it just belches out black smoke.

On the rare occasion when it decides to run good we test drive around the block a couple times (~1/3 mile) and it will be just fine-good power, no hesitation, no smoke! Then for some reason it loses power rapidly, idle rough and starts to exhaust black smoke. It'll barely make it back up the driveway.

History:
-car had a bad knock when we bought it but the body/interior was worth the $ we paid (next to nothing).
-Had the engine (block) rebuilt; knock was a bad bearing on one of the connecting rods.
-After that the car ran "ok" but was lacking power, hesitant, etc. Found that the cat. converter was plugged. Had that replaced.
-Car ran much better but mechanic that replaced the cat. told us the carb was flooding and that probably diluted the oil which caused the rod bearing to go bad in the first place. He suggested we get the carb. replaced asap.
-we've installed two rebuilt carbs since then and neither made a difference. It's still running too rich and although it will run "perfect" very intermittently, most of the time it runs like sh*t. The outside temperature doesn't seem to have any affect on how it runs. It can be warm outside or it can be cool; doesn't make any difference.

We've installed new spark plugs (old ones were fouled of course). Installed new O2 sensor. The timing is set up properly.

Running out of ideas here. If we could just figure out why the car is running too rich it would be a beautiful running car. We paid very little for the car but it is in terrific condition-clean, solid straight body, no rust, excellent interior, etc. It's getting harder to find them in good condition.

Any help would be most appreciated. I'm getting ready to throw in the towel...

 

first thing i would check at this point is fuel pressure.

 

Shouldn't the pressure from a mechanical fuel pump be constant?

How can I check the pressure to see if it's correct?

 

normally with mechanical pumps the problem is not enough fuel volume to feed the motor, but i have seen a few pumps that would put out too high a pressure which will push the needle off the seat & cause the carb to flood.
it is very rare & may not be your problem, but it does happen.

if you want to let it run for a few minutes while checking, you will need to Tee into the line between the pump & carb. a trip to the wrecking yard for a fitting that goes into the carb & a stop at the parts house for some fuel hose, a Tee, & some clamps should get you what you need. if you don't have one, most vacuum gages also will read fuel pressure up to around 7 pounds.
once you have the fuel line removed from the carb, you should be able to slide the nut down the line enough to push some rubber hose over the flare & put a clamp it.

sense the carb holds some fuel in the bowl, putting the gage right on the carb end of the fuel line should be fine, just push the rubber hose over the flare, put the gage on, clamp everything & start it up.
watch for fuel leaks, of course no smoking, & have a fire extinguisher handy

 

It's not whether it's constant you need to check, it's what the presure going to the carb is. To much pressure will cause gas to push past the inlet needle, and could cause the carb to flood.

First thing I would check is the float level. To high can cause it to flood also. Even though you have rebuilt carbs, that doesn't mean it is setup correctly for your vehicle.

Here's info on checking the fuel pressure.

http://www.prismenterprise.com/mityv...lpressure.html

 

Thanks for the tips about fuel pressure. I'll see if I can get something rigged up to check it.

 

I would start with simple things (low dollar)...thats what i always do.

I would start with the choke make sure its adjusted properly......at the very least put a rubber band on it and hold that mother ****er open that way you KNOW its not closing on you and see if it runs any better...... if it does theres your problem and you can adjust it.........make sure that its not sticking..........it is possible that there is not an adequate heat source to the carb.......... or if its an electric choke the engine temperature sensor could be bad..............then i would move on to the gas tank..........try taking off your gas cap and see how it runs drive it a little bit if it seems like its running better........if you take off the cap and it sucks like a vacuum cleaner then thats a very possible source for your problem.....vented gas caps dont cost anything but like 19 bucks...............its very very very possible the the fuel tank vent is cloggend with ****......... then i would check the float.......you can sink your float if backfireing keeps happening through the carb, in that case a new ne can be ruined the first time you backfire through the carb and then you will never know what the hell is going on.........

The "prime" setting bypasses the vacuum function and allows fuel to flow at all times, even when the engine is stopped. The purpose of this setting is to allow the carb float bowls to be filled when the engine is not running. Note that if you run your petcock(s) on the prime setting all the time, you lose the safety feature provided by the vacuum petcock. Note also that on this setting, fuel is prevented from flowing out through the carbs, into cylinders, etc.) only by the float valves in the carbs, which close when the carbs are full. Should one of these float valves stick open or leak, you then get flooding through that carb.

THAT MEANS IF YOUR TANK IS NOT VENTING YOU FLOOD YOUR ****.........................

hope that helps brother

 

Of course, if he hasn't gotten it fixed in the last 22 months. . .

 

did any of these rebuilt carbs have new electrical components added like the MCS (mixture control solenoid), or Throttle Position sensor?

my old 84 SC had a similar problem where the MCS itself from time to time work, and then stop working, and then work later that day.....eventually I replaced it before I got rid of the car. My temporary solution was drilling out out the end of the baseplate so I could get to the mixture adjustment screws (your carb is an E2ME, right?) I would run it a turn and 3/4 out from seated when it was cold, drive it, saw what happened when the car went into closed loop...if it threw "check engine" I'd pull over and adjust the mixture screw leaner if it started bogging or running rich. Most times the "Check engine" light would go off when I did this, but not always.

It was kind of a headache, and probably not the solution your looking for, but its just something to consider. My 84 was my primary transportation for a couple months, so I had to kind of band-aid it. Until I could have the car down for a day or longer.

Good luck...hopefully you'll figure it out soon!