No Fuel / vapor return line, engine running very rich
#2567982
10/22/18 08:07 PM
10/22/18 08:07 PM
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Joined: Jun 2007
Posts: 1,167 clarks summit pa
73cuda340
OP
super stock
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OP
super stock
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clarks summit pa
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Is it possible that by not having a fuel return line installed on a carburetor equipped car, the motor would run excessively rich? I don't see how it would be possible, but i just read this recently. The reason that I'm asking is because my motor in my car is running extremely rich and I have taken everything apart and cleaned everything up in both carburetors numerous times and nothing seems to fix the issue. The motor is a brand new 528 hemi with two edelbrock 600's on it. I have a fuel pressure regulator installed and set it at 5 psi, so there's not too much pressure pushing past the needle and seat. I installed the lightest step up springs in the carburetors to help hold down the metering rods at idle. I don't have any vapor locking issues. I'm at a loss at this point of what the problem is and that's why I was even considering this as a possibility. I don't see how this would fix it, but I'm willing to try adding one at this point.
1973 Cuda 528 all aluminum Hemi, 4 speed, 3.23 Sure-Grip,
(JA5) Silver Frost Metallic
1973 Challenger Rallye 340
1985 W150 Power Ram prospector
1986 Camaro IROC-Z 305 tpi
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Re: No Fuel / vapor return line, engine running very rich
[Re: 73cuda340]
#2568386
10/23/18 03:06 PM
10/23/18 03:06 PM
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Joined: Jan 2008
Posts: 2,592 None
71rm23
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master
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Re: No Fuel / vapor return line, engine running very rich
[Re: BcudaChris]
#2568547
10/23/18 08:17 PM
10/23/18 08:17 PM
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Joined: Jun 2007
Posts: 1,167 clarks summit pa
73cuda340
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Sounds like you have a dead-head regulator, so shouldn't need a return line. If your tank isn't vented though (your title and post seem to contradict a bit describing a vapor return line and a fuel return line) that can cause problems.
Your car should have a tank with 4 vent tubes on the front, a little 4 tube vapor separator and a 1/4" line running from said separator to the charcoal canister. I am assuming you mean this line by "vapor return line". If this line is plugged, it may cause what you describe.
If you put in a 3/8" or bigger fuel pickup, you'll have a return port on the sender. In my case, I ran a new 3/8" fuel line and used the existing 5/16" line as a fuel return line. I have my vent line connected in the factory manner.
Basically, if the tank vent line is connected and venting properly, I think you can rule this scenario out in your troubleshooting. The regulator that I have is a Holley HP Billet 12-840. It only has an inlet and two outlets with one of the outlets plugged. I have the four vent tubes from the gas tank hooked up to the vapor separator and the line that went to the charcoal canister I have venting to the air since I removed the charcoal canister. I have a 1/2" fuel sending unit that has a return port on the sender that I just plugged since I don't have a fuel return line. Is there any issue with this being plugged? The car has edelbrocks so there is no power valve in the carburetors.
1973 Cuda 528 all aluminum Hemi, 4 speed, 3.23 Sure-Grip,
(JA5) Silver Frost Metallic
1973 Challenger Rallye 340
1985 W150 Power Ram prospector
1986 Camaro IROC-Z 305 tpi
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Re: No Fuel / vapor return line, engine running very rich
[Re: tman]
#2568565
10/23/18 08:59 PM
10/23/18 08:59 PM
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Joined: Jun 2007
Posts: 1,167 clarks summit pa
73cuda340
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super stock
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OP
super stock
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clarks summit pa
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It's extremely rich the entire time that its running. It burns my eyes even standing next to it at idle in the garage and if I take it for a ride my clothes will smell like gas by the time I'm done driving it. The car is hard starting and loads up pretty bad when you first go to drive it. I bought a Innovate LM-2 meter to get the actual ratio that it's at; I just haven't gotten around to installing it yet. I never changed the jets since they are the same ones that were in it when the motor was set up on the dyno.
1973 Cuda 528 all aluminum Hemi, 4 speed, 3.23 Sure-Grip,
(JA5) Silver Frost Metallic
1973 Challenger Rallye 340
1985 W150 Power Ram prospector
1986 Camaro IROC-Z 305 tpi
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Re: No Fuel / vapor return line, engine running very rich
[Re: 73cuda340]
#2568569
10/23/18 09:14 PM
10/23/18 09:14 PM
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Joined: Mar 2005
Posts: 1,406 New Jersey, USA
yella71
pro stock
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pro stock
Joined: Mar 2005
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New Jersey, USA
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maby your floats are too high...have you gone through the carbs or are they right out of the box? Ive seen a few of those carbs need work brand new to make them right, Im guessing yours are some of those carbs
Last edited by yella71; 10/23/18 09:16 PM.
71 challenger convertable, 64 sport fury 383 ci with factory air
99 sebring convertable
89 CTD pup
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Re: No Fuel / vapor return line, engine running very rich
[Re: yella71]
#2568576
10/23/18 09:27 PM
10/23/18 09:27 PM
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Joined: Jun 2007
Posts: 1,167 clarks summit pa
73cuda340
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They claimed that they set the carburetors up when the motor was on the dyno. I've had nothing but issues with it since I bought it.
1973 Cuda 528 all aluminum Hemi, 4 speed, 3.23 Sure-Grip,
(JA5) Silver Frost Metallic
1973 Challenger Rallye 340
1985 W150 Power Ram prospector
1986 Camaro IROC-Z 305 tpi
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Re: No Fuel / vapor return line, engine running very rich
[Re: 73cuda340]
#2568581
10/23/18 09:42 PM
10/23/18 09:42 PM
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Joined: Jan 2003
Posts: 20,644 So Near, Yet So Far
topside
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Too Many Posts
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My '68 Hemi RR was also very rich, stock carbs but big cam (low vacuum signal), chassis dyno guy didn't tune it out although claiming he did... Later on my racer-guru buddy changed the springs, needles & jets to what he was running in his Hemi Bee (which was more stock) and that cured it. Made more power, too. Car had lost its separator before I bought it; I ran a Carter electric pump, 1/2" line, mech pump, regulator 6PSI, only the OEM tank vent line. No problems.
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Re: No Fuel / vapor return line, engine running very rich
[Re: 73cuda340]
#2568727
10/24/18 06:15 AM
10/24/18 06:15 AM
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Joined: Aug 2007
Posts: 566 WA
tman
mopar
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mopar
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WA
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I too think you need to check floats. Not too bad of a job, many videos on how to do it. You will have starting and driveability issues with floats too high. This video is not bad and shows how to take top off: https://www.youtube.com/watch?v=wR_AfQjyT-A
Last edited by tman; 10/24/18 06:25 AM.
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Re: No Fuel / vapor return line, engine running very rich
[Re: 71rm23]
#2569168
10/24/18 11:28 PM
10/24/18 11:28 PM
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Joined: Feb 2005
Posts: 28,312 Cincinnati, Ohio
Challenger 1
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Cincinnati, Ohio
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Again, power valve????????? Are we missing something? His carbs do not have power valves.
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Re: No Fuel / vapor return line, engine running very rich
[Re: Challenger 1]
#2569176
10/24/18 11:44 PM
10/24/18 11:44 PM
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Joined: Jan 2008
Posts: 2,592 None
71rm23
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master
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Again, power valve????????? Are we missing something? His carbs do not have power valves. Well, sorry Challenger1 or anyone. Just a suggestion
Last edited by 71rm23; 10/24/18 11:44 PM.
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Re: No Fuel / vapor return line, engine running very rich
[Re: 71rm23]
#2569198
10/25/18 12:58 AM
10/25/18 12:58 AM
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Joined: Jun 2007
Posts: 1,167 clarks summit pa
73cuda340
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OP
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clarks summit pa
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I checked the float height and drop the last time that I had them apart and set them to edelbrocks recommendation. I guess that I could try lowering them a tiny bit more. The car has two 600 cfm performer series carbs. No vanke mod on the intake and I'm not sure what size jets or rods are in them. The vacuum at idle is very low, I want to say it was at 4 or 5" of vacuum at idle going off of memory. I installed the lightest springs that edelbrock makes for the metering rods. I'll try to get the lm 2 hooked up soon to get some air fuel ratios.
1973 Cuda 528 all aluminum Hemi, 4 speed, 3.23 Sure-Grip,
(JA5) Silver Frost Metallic
1973 Challenger Rallye 340
1985 W150 Power Ram prospector
1986 Camaro IROC-Z 305 tpi
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Re: No Fuel / vapor return line, engine running very rich
[Re: 73cuda340]
#2569238
10/25/18 06:54 AM
10/25/18 06:54 AM
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Joined: Aug 2007
Posts: 566 WA
tman
mopar
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mopar
Joined: Aug 2007
Posts: 566
WA
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Re: No Fuel / vapor return line, engine running very rich
[Re: tman]
#2569485
10/25/18 06:58 PM
10/25/18 06:58 PM
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Joined: Jun 2007
Posts: 1,167 clarks summit pa
73cuda340
OP
super stock
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OP
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Posts: 1,167
clarks summit pa
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I have the tuning guide that came with the carburetors. I think it's the same one.
1973 Cuda 528 all aluminum Hemi, 4 speed, 3.23 Sure-Grip,
(JA5) Silver Frost Metallic
1973 Challenger Rallye 340
1985 W150 Power Ram prospector
1986 Camaro IROC-Z 305 tpi
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