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Return fuel line need or not?

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Old 06-25-2012, 08:27 PM   #1
thiatt
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Default Return fuel line need or not?

The other day I was covering my 77 after long drive and smelled gas near rear passenger side. Looked under car seen small puddle of fuel, dripping from frame. Using mirror seen rubber line from tank was leaking just before meeting hard line on frame.
Here is my question, should my return line be connected to system? Once apon a time previous owner unhooked and capped it. Could this cause pressure to hold in line cause it to fail, and cause rich conditions by over filing carb to point float and needle can't stop flow? Also when pressure checked pump had 13 psi.

Thanks for listen T
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Old 06-25-2012, 10:40 PM   #2
1986coupe
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The piece that you need isn't that expensive. If you have a fuel leak in that part of the car that is the most common area for engine fires with C3's. Why take the risk, just replace it.
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Old 06-25-2012, 11:22 PM   #3
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13 psi is too much.
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Old 06-26-2012, 12:59 AM   #4
Frank_Nesta
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13 PSI is too high. It is caused by not having a return line to the fuel pump. I am surprised it is not flooding the carb????
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Old 06-26-2012, 06:44 AM   #5
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Seems like you have more than one problem there. As mentioned, 13 psi to the carb is to high, and tough on the float valve needle and seat. Should be more like 5-7 psi. Doubt a plugged return line from the pump has much to do with it, as only a small oriface fitting. Return line's a good idea though, as helps keep the fuel supply cooler, by looping some back to the tank. Really be more worried about the fuel pump 13 psi though, as that's the one sure to cause problems.
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Old 06-26-2012, 11:27 AM   #6
Frank_Nesta
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Quote:
Originally Posted by Vette5.5 View Post
Seems like you have more than one problem there. As mentioned, 13 psi to the carb is to high, and tough on the float valve needle and seat. Should be more like 5-7 psi. Doubt a plugged return line from the pump has much to do with it, as only a small oriface fitting. Return line's a good idea though, as helps keep the fuel supply cooler, by looping some back to the tank. Really be more worried about the fuel pump 13 psi though, as that's the one sure to cause problems.
I have seen it with my own eyes and a carb expert agreed with our findings. Installed a 77 Corvette engine in a old chevy truck with no return line. Used a new 77 Corvette fuel pump, blocked the return line hookup, experienced 13 PSI and flooding at the carb, Changed to a older model fuel pump without the return connection and all was well.
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Old 06-26-2012, 04:58 PM   #7
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I run 6psi with no return in my 70 with no issues.
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Old 06-26-2012, 07:46 PM   #8
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Thanks everyone. It is a aftermarket pump, I also thought 13 psi seen high for a carb.
Next question, if unable to find pump with less pressure would a regulator do the trick?
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Old 06-26-2012, 08:39 PM   #9
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Don't know why a pressure regulator won't work. But I suppose it could cause issues with the stock type mechanical pump.

I have a electric pump and a pressure regulator on my 69 350/350 and it works well.


Previous owner had some local "mechanic" install the electric pump which was feeding the mechanical pump, and things went all to hell.
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Old 06-26-2012, 08:42 PM   #10
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Based on "Frank's" observations, maybe redo the return line first, as good idea anyway. On rarely driven cars, I've been going rear mounted electric fuel pumps for many reasons. Mallory's 140 set up with engine mounted regulator seem's to be problem free. Still use an orfaced return line, and pressure gauge on the regulator, to keep an eye on things.
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Old 06-26-2012, 09:11 PM   #11
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From personal experience to much pressure can cause the carb to leak and then the cylinders star to fill up with gas and it wont turn over and or much worse.
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Old 06-26-2012, 09:16 PM   #12
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Quote:
Originally Posted by FKING1 View Post
I run 6psi with no return in my 70 with no issues.
Me too...but mine is a '75.
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Old 06-26-2012, 10:26 PM   #13
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Exellent, now does anyone have pic of how this return fuel line hooks into system? 77 gm service manual doesn't show it, neither does chiltons can't seem to find part that would "T“ into system in any of my wonderful catologs!?!

Thanks again T
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Old 06-26-2012, 10:31 PM   #14
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No pics handy,
From the pump, rubber hose to 1/4" metal line
To pass sideof gas tank
To rubber line to top of gas tank 1/4" nipple.
There is no "T"
Pump has separate return nipple.
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Old 06-26-2012, 10:36 PM   #15
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Wait a minute i'm no dummy, there is suppose to be two ports on fuel pump. Now I know why return isn't hooked up.
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Old 06-26-2012, 10:40 PM   #16
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3 ports

Inlet, outlet, return
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Old 06-26-2012, 10:46 PM   #17
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Quote:
Originally Posted by noonie View Post
3 ports

Inlet, outlet, return
A yeah... Thats what I meant lol. Mine has only two in and out. Wish I was smart enough to post pics from phone, never paid much attention to it but this pump is huge. Must b for motors much faster than mine.
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Old 06-26-2012, 11:08 PM   #18
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You can get the correct one anywhere like Autozone for around 30 bucks and it will be regulated for a max of 9 psi or less
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Old 06-27-2012, 04:27 PM   #19
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Quote:
Originally Posted by noonie View Post
You can get the correct one anywhere like Autozone for around 30 bucks and it will be regulated for a max of 9 psi or less
My Summit Racing pump is 6 to 7 psi.
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Old 06-27-2012, 08:48 PM   #20
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Again thanks for all the info every one. I will pick up pump from auto zone tomorrow. I'll post end result once new pump and leak are fixed.
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Old 06-27-2012, 08:48 PM
 
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