Rich fuel problem
Thread Starter
Heel & Toe
Joined: Aug 2022
Posts: 16
Likes: 1
Rich fuel problem
Hey guys, I just installed a new intake and carburetor in my ‘76 with a 350 engine. The mixture screws are turned out 2 1/2 turns. On the first start up it ran pretty good. After about 3 to 4 minutes I noticed a pretty significant fuel puddle in the rear near the tank.
Now that I have repaired the fuel leak it will not start and stay running. It seems to be extremely rich. Black smoke, and strong fuel odor.
my thoughts are that the fuel pump pressure is too high but with the leak it was restricting the pressure and that’s why it ran fine with the leak. Does anyone agree with that diagnosis or should I be looking for something else? Thanks.
Now that I have repaired the fuel leak it will not start and stay running. It seems to be extremely rich. Black smoke, and strong fuel odor.
my thoughts are that the fuel pump pressure is too high but with the leak it was restricting the pressure and that’s why it ran fine with the leak. Does anyone agree with that diagnosis or should I be looking for something else? Thanks.
Melting Slicks
Joined: Jul 2006
Posts: 2,291
Likes: 492
From: Salmon Arm, BC
Sounds to me like the fuel pressure (now that the leak is fixed) is overpowering the float needle seat and flooding the carb with fuel. You didn't really say, but do you have an electric pump at the tank? If you do, it would need a fuel pressure regulator to limit the fuel pressure to around 6 PSI.
You should measure and see what the fuel pressure is now, so you know.
You should measure and see what the fuel pressure is now, so you know.
Pro
Joined: Nov 2023
Posts: 701
Likes: 335
From: Aubrey TX
Sounds to me like the fuel pressure (now that the leak is fixed) is overpowering the float needle seat and flooding the carb with fuel. You didn't really say, but do you have an electric pump at the tank? If you do, it would need a fuel pressure regulator to limit the fuel pressure to around 6 PSI.
You should measure and see what the fuel pressure is now, so you know.
You should measure and see what the fuel pressure is now, so you know.
Pro
Joined: Aug 2000
Posts: 610
Likes: 168
From: Vancouver B.C.
Personally I would keep the return. Prevents vapor lock. Before the intake and carb change, was it running rich? If not, I’d be looking at the carb. But testing the fuel pressure would be first things. Over 6-7 pounds could cause nozzle drip. With the engine idling check to see if you can see fuel dripping out of the venturis. I had this problem. I installed a new fuel pump. Tested at 9 psi. Had to get a pressure regulator to stop nozzle drip. Nozzle drip could also be caused by an intake vacuum leak topside or on the valley oil side. The leak makes the engine want more fuel so it pulls it at idle in the form of nozzle drip. To recap. Easy first. Check for nozzle drip at idle. Get a tester and check fuel pressure. Next consider that maybe the Carb float is not seating. Consider Intake leak.
good luck. Keep us posted.
good luck. Keep us posted.
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Tech Contributor
Joined: Aug 1999
Posts: 14,379
Likes: 6,390
From: At my Bar drinking and wrenching in Lafayette Colorado
There is no such thing as a brand new Rochester. It sounds like you bought a "remanufactured" carb, which is a complete pile of junk. If you bought a "reman", e-mail me for my paper about those carbs to give you a list of all the issues that will be a problem with that "new" carb. I would predict it runs like crap...
Lars
Lars
Race Director
Joined: Mar 2017
Posts: 11,949
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From: Virginia
Tech Contributor
Joined: Aug 1999
Posts: 14,379
Likes: 6,390
From: At my Bar drinking and wrenching in Lafayette Colorado
Advanced
Joined: Mar 2006
Posts: 68
Likes: 28
Most here will agree that if it is one of these 'new Quadrajets', for the money laid out for it you could have probably put that towards the original and been much farther ahead.
If the original is still around, take some good pics of all sides with carb# and someone will be able to atleast tell you if it is serviceable.
Once that is determined, you could do a couple things.
Send it off to Lars for a complete rework.
Tackle it your self. With good parts, a book or two and help from here it isnt to bad if you have any mechanical ability.
Or you could locate someone close by with a good understanding of Quadrajets and have them help you through it.
Try local old school shops. Check with local car clubs. Can even look around for retired GM dealer mechanics.
If you thow out a location of where you are at, may even be someone from here that can swing by and give a hand.
Most guys(and gals)that are into the old car hobby will go out of their way to help educate any newbie in this 'sport'.
If the original is still around, take some good pics of all sides with carb# and someone will be able to atleast tell you if it is serviceable.
Once that is determined, you could do a couple things.
Send it off to Lars for a complete rework.
Tackle it your self. With good parts, a book or two and help from here it isnt to bad if you have any mechanical ability.
Or you could locate someone close by with a good understanding of Quadrajets and have them help you through it.
Try local old school shops. Check with local car clubs. Can even look around for retired GM dealer mechanics.
If you thow out a location of where you are at, may even be someone from here that can swing by and give a hand.
Most guys(and gals)that are into the old car hobby will go out of their way to help educate any newbie in this 'sport'.
Race Director
Joined: Nov 2006
Posts: 13,227
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From: Sunshine Coast, Queensland, Australia
2025 C3 of the Year Finalist - Modified
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Cruise-In VIII Veteran
I'm with Lars. There is no such thing as a brand new Rochester carb.
Sounds like a reman or a Chinese knock off.
Waste of money.
Sounds like a reman or a Chinese knock off.
Waste of money.
Team Owner
Joined: Jan 2007
Posts: 53,648
Likes: 878
From: Southern Cal Ca
St. Jude Donor '22
my first thought was one of the new man'd rochesters I read about.
76/350 what? L48 or L82?
is it plumbed like orig, vaper can, vac lines?
need pics and model number in the off chance carb is not junk
76/350 what? L48 or L82?
is it plumbed like orig, vaper can, vac lines?
need pics and model number in the off chance carb is not junk