Automotive Forums .com - the leading automotive community online! Automotive Forums .com - the leading automotive community online!
Automotive Forums .com - the leading automotive community online! 
-
Latest | 0 Rplys
Go Back   Automotive Forums .com Car Chat > Engineering/Technical
Engineering/Technical Ask technical questions about cars. Do you know how a car engine works?
View Poll Results: carburator
[url](value}[url] 0 0%
0 0%
Voters: 0. You may not vote on this poll

Reply Show Printable Version Show Printable Version | Email this Page Email this Page | Subscription Subscribe to this Thread
 
Thread Tools Search this Thread
Old 02-26-2005, 09:30 AM   #1
carbhater
AF Newbie
 
Join Date: Feb 2005
Location: Davenport, Iowa
Posts: 3
Thanks: 0
Thanked 0 Times in 0 Posts
Angry feedback carburater

my 1984 F-150 runs rough. fuel mixture way to rich. Burns my eyes when I try to work on it running. what is a good starting point for Idle mixture and fast idle cam? Also is there anyway to bypass all that emissions stuff. Also airpump is rusted out and of no use. Surely there is some "Jerry Rigging I could perform". Any help would be greatly appreciated. NOTE: I have remove the EGR completely and replaced with a plated.
carbhater is offline   Reply With Quote
Old 02-27-2005, 01:35 AM   #2
curtis73
Professional Ninja Killer
 
curtis73's Avatar
 
Join Date: Nov 2002
Location: Penn Hills, Pennsylvania
Posts: 3,561
Thanks: 0
Thanked 9 Times in 9 Posts
Re: feedback carburater

It depends on the carb. Most will run fine over a wide range of settings, but depending on the carb the bench setting could be 1, 1.5, or 2 turns out from seated. Try taking them both in by a half turn or so but remember where you were.

you also didn't say if something else changed. Did you change cams, calibrations, switch carbs... A factory carb would not suddenly go out of tune. If it was running fine before, the idle mixture isn't to blame.

I would look first to the float. They get logged and sink allowing fuel to continue to pump in after the bowl is full. The extra fuel just spills right into the throats and causes rich operation.

It could also be a vacuum leak. I know it sounds counter-intuitive, but vacuum leaks can cause fluctuations in idle vacuum that make very uneven fuel distribution in the runners. The overall result is an average lean condition, but one or more cylinders run very rich and the exhaust smells like gasoline. You can chase down vacuum leaks with some starting fluid or brake parts cleaner. Spray short bursts at gasket mating surfaces. If the idle changes (smooths out, increases) then you've found a leak.

Also, some fuel pumps have one "in" and two "outs". The second out is a return to the tank. If it gets plugged or restricted, the pump will deliver more than required pressure which will overpower the float and cause a rich condition.

The idle mixture screws are designed to dance around very close to ideal tune, but wouldn't be responsible for that much of a rich condition on their own.
__________________
Dragging people kicking and screaming into the enlightenment.
curtis73 is offline   Reply With Quote
Old 02-28-2005, 10:50 AM   #3
carbhater
AF Newbie
Thread starter
 
Join Date: Feb 2005
Location: Davenport, Iowa
Posts: 3
Thanks: 0
Thanked 0 Times in 0 Posts
Thumbs up

First of all let me thank you for your swift,and informative reply.I think I may have found the culprit (vac) leak, but it still might involve the float. I must say you are better than the Haynes repair manual. lol Eddie the Carbhater signs off.
carbhater is offline   Reply With Quote
Old 02-28-2005, 11:25 AM   #4
curtis73
Professional Ninja Killer
 
curtis73's Avatar
 
Join Date: Nov 2002
Location: Penn Hills, Pennsylvania
Posts: 3,561
Thanks: 0
Thanked 9 Times in 9 Posts
Re: feedback carburater

Just glad I could help
__________________
Dragging people kicking and screaming into the enlightenment.
curtis73 is offline   Reply With Quote
 
Reply

POST REPLY TO THIS THREAD


Bookmarks
Go Back   Automotive Forums .com Car Chat > Engineering/Technical

Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off



All times are GMT -5. The time now is 07:58 PM.

Community Participation Guidelines | How to use your User Control Panel

Powered by: vBulletin | Copyright Jelsoft Enterprises Ltd.
 
 
no new posts