QJet running rich - Help!

[crawdad]

I recently replaced the Quadrajet 4bbl on my truck with a newly rebuilt one. It came all painted up, looked better than a new one. It was suppose to have a new choke, new float, leaking ports all epoxied up, etc., I guess you could say the typical rebuild. The replacement carb made a big difference in the way my truck runs (much better). I had to adjust the idle mixture, it was off quite a bit. The only thing now is it seems like it is running real rich. I'm basing this on the fact that it smells rich. I can open the door and you can smell the gas. If I walk back toward the exhaust pipe, I smell like I've been taking a bath in gasoline. The truck is a little rough until it warms up, but it runs real good after that, but still I get the rich smell. I don't think this is normal is it? Is there anything else I can check to determine why is smells so rich? Am I going to have to go into the carb and adjust the float level or something (Lord I hope not). Any ideas you guys could throw at me would be much appreciated.

[VetteVet]

This is written by an expert on Q-jets.
http://www.lbfun.com/Corvette/Tech/v...ng%20Paper.pdf

[68speedalert]

Did you adjust the idle mixture this way?


http://67-72chevytrucks.com/vboard/s...d.php?t=224096

Otherwise, where did the 'rebuilt' unit come from?

A float set too high will make it idle rich.

Is the choke wide open after it's completely warm?

[crawdad]

Originally Posted by 68speedalert

Did you adjust the idle mixture this way?


http://67-72chevytrucks.com/vboard/s...d.php?t=224096

Otherwise, where did the 'rebuilt' unit come from?

A float set too high will make it idle rich.

Is the choke wide open after it's completely warm?

I adjusted the idle mixture to highest vacuum with a vacuum gauge. I bought the carb off of e-bay (probably my biggest mistake) from a guy called mountain man carburetors, or something like that. On outward appearance it looks as though he did a decent job, however I know that is not an indication on the quality of the work on the inside of the carb. The choke is wide open after it warms up. Like I said, the carb works great except for the rich smell (real rich). I'm starting to think that the float was probably set too high and it looks like I'm going to have to take the top off. Dang it!

[WorkinLonghorn]

Have you pulled a plug to look for carbon? Do you see any black smoke at any point? Have you thoroughly checked for leaks in the fuel line?
>> I actually had a Q-Jet once that would have a float valve stick open occasionally and gas would overflow out the vent.

[Boog]

Could it be after having driven these late model fuel injected vehicles for a while your truck smells rich because it is more so than the newer ones? The newer ones run much much leaner. The older carb'd ones do smell of gas naturally. If the spark plugs are blackened up then it probably is in need of some carb adjustment. My 97's exhaust smell clean compared to my 69 and it is a fresh build.

[crawdad]

Originally Posted by cougar

Have you pulled a plug to look for carbon? Do you see any black smoke at any point? Have you thoroughly checked for leaks in the fuel line?
>> I actually had a Q-Jet once that would have a float valve stick open occasionally and gas would overflow out the vent.

No, I haven't pulled the plugs yet. I was going to do that this weekend and replace if necessary. There is no black smoke from the exhaust at all that I can tell, though the end of the exhaust pipe is black. Haven't checked for fuel line leaks...what would this do other than cause mileage to go way down? But, anyway, I haven't noticed any leaks, but have not thoroughly gone over the lines. No leaks from the carb itself, clean as a whistle.

[crawdad]

Originally Posted by Boog

Could it be after having driven these late model fuel injected vehicles for a while your truck smells rich because it is more so than the newer ones? The newer ones run much much leaner. The older carb'd ones do smell of gas naturally. If the spark plugs are blackened up then it probably is in need of some carb adjustment. My 97's exhaust smell clean compared to my 69 and it is a fresh build.

Boog, I've wondered the same thing myself. Maybe it's my nose that's in need of a tune rather than the carb. Honestly, though, I don't think there has ever been a time when I didn't own at least one vehicle with a carb. If I stand by the exhaust pipe of my truck for just a short while, my wife jumps my rear when I come in, makes me go outside and change clothes. I'll tell you though, when I'm up to speed, this carb runs as slick as an onion. I know you can't smell an exhaust pipe at 70 mph however, but most of the problem seems to be when at an idle.

[jhow66]

How many turns out from closed are the needles?

[crawdad]

Originally Posted by jhow66

How many turns out from closed are the needles?

I honestly don't remember. If I had to guestimate, I'd say around 4 turns out, but that's just guessing. Seems like I've been loosing memory cells at a rapid pace here lately. I do think I'll start from scratch again with the mixture screws by turning them both back in and then back them out about 2 1/2 to 3 turns and then re-check the mixture keeping up with how much I have to turn them. At least I'll know then.

[68speedalert]

Run them out until your vacuum peaks. Then, slowly, by 1/4 turns, turn them back in, alternately, until the vacuum just drops. You'll also hear the RPM's drop a little. Open the screws back out about a 1/4 or so (so vacuum & erngine smooths out).

If you didn't turn them back in, you are running rich.

BTW, don't pull all the plugs, just a couple easy ones. I would reajust the mixture like I described before that.

Also , look down the throat of the barrels and check for ANY visible fuel dripping from ANYWHERE, with the engine running and warmed up, at base idle.

[WorkinLonghorn]

Haven't checked for fuel line leaks...what would this do other than cause mileage to go way down?

Well yeah,but also it would make the truck smell like gas.
>>Check a plug or two as mentioned above for sooty residue which indicates rich mixture.

[crawdad]

Ok, thanks for the suggestions. I'll do all of this and then post back the results.

[vfrdude]

You might want to verify the choke is set up correctly.....

[cruiserman]

Check the float level. It may be stuck open. Sometimes crud from the tank gets through the filter and messes with the float.

[CST*TEN in Katy]

I bought a rebuilt Q-jet from O'Reilley a couple of months ago. It smelled gassy after the first week, I never had to choke or pump to start it cold. I took the carb apart and the "epoxy" on the bowl ports crumbled apart. It had the consistency of feta cheese. I put JB weld on, thet fixed the leaks, bit I'm still not happy with it. I can't get enough vacuum to open the secondaries. I'm gonna clean up my 600 Holley and see how long I can make it run before the float needles stick open and it dumps gas.

[68speedalert]

Originally Posted by CST*TEN in Katy

......bit I'm still not happy with it. I can't get enough vacuum to open the secondaries. ..... 600 Holley and see how long I can make it run before the float needles stick open and it dumps gas.

You will not be able to get the secondaries to open with the engine in park or neutral.

If you want to see them open you're gonna have to have someone braketorgue it while you watch the flaps on the secondaries.

Generally, that's not a great idea, for safety reasons.

I can tell if they're opening by the sound of all that air sucking in when I floor it while driving.

You can compare how it sounds without the sec. by flooring it with the engine cold, (because the choke is closed). The choke has a sec lock-out that keeps the sec from coming on until it's wide open.

BTW, the Holley 600 is the carb that turned me against Holleys.

As a rule, never buy a rebuilt carb from a parts store.....fix what you got.