paulldove@live.

82 camaro Z28 305 with 1406 Edelbrock...

Problem is... Replaced Mechanical Pump with old Electronic Diaphram Pump i had laying around that had 6-9 psi on it... Lasted for one week and burned up last night.... Purchased http://www.autozone.com/autozone/par...ier=191411_0_0_
After installing this pump i noticed the Fuel line i had previously ran to the old pump had a larger diameter line than the new one which now makes me think i was using the return line as the supply line...

Question is... on the passenger side wheel well are two fuel lines... One small and bigger... Which one is supply and which one is return?

Project 3.4 Camaro

Supply fuel line is always larger, at least this is true of MPFI, but the same principal applies, so I am 99.99999999% sure it is true of carb as well, since more fuel goes in, then comes back out because the engine uses a good portion of what goes into it, fuel system only sends back out the excess.

paulldove@live.

Fudge, That is what i thought as well... On the new pump has a smaller diameter outlet so the larger hose does not seat on it right... No matter how much i tighten hose clamp the hose still spins and small leak... The Outlet on the pump in not interchangable unfortunately. just looked on hose and it says 3/8" diameter Guess i need to go get 5/16" line then... Thanks for confirming!

bradley23150

iTrader: (10)

Correct.

3/8" is Feed (Large)
5/16" is Return (Small)

jchaussee

What about on TPI cars that have been converted to carb. Then you have three lines. Which are which

//<86TA>\\

iTrader: (15)

no, its still 2, and the sizes are the same, they are just on different side of the engine bay, and have different connections. FWIW, most, if not all 3rd gens have 4 lines from the tank.

Project 3.4 Camaro

Only 2 of them carry fuel, one goes to a filter/vent on driverside wheel well, the other is for the EVAP can if memory serves.

bradley23150

iTrader: (10)

-Carb'd cars:
*2 lines on passenger side:
Feed (3/8")
Return (5/16")
*1 line on driver side
Evap canister (5/16")

-FI Cars
*3 lines on drivers side
Feed (3/8")
Return (5/16")
Evap line (5/16")

Evap line runs to the charcoal canister

4 lines come out of the tank on all third gens, just one ends at the tank through a vent.

That should clarify.

jchaussee

That does clarify but with the evap and return which one is which. One is above the other. I don't have a canister so I can't see which one went to it

jchaussee

So I was outside working on my car to hook up fuel lines, and noticed all three were diffent sizes. So big was supply. Hooked it up. I assumed the next size was return. So I hooked it up. Was that correct? And the smallest the I assumed was vapor and just ren a lenth of hose outside of car. So was it correct??

Camarobuild18

looks like it. Isnt evap to pressurize the tank? Maybe thats why my fuel system with my TBI isnt working so well?

Project 3.4 Camaro

No, evap isn't for pressurizing the tank, its for catching fuel vapor from the gas tank I believe, while the other non fuel carrying line is for preventing pressure build up in the gas tank.

InfernalVortex

iTrader: (4)

I notice most other people have pointed out that there is a feed line, return line, and a vent line.... The 4th line is actually a brake line from the master cylinder I think... But there's definitely a 4th line going through the trans tunnel that's routed with the fuel lines and looks identical.

Project 3.4 Camaro

As someone who has replaced the fuel pump I know for a fact that there are 4 lines coming out of the tank.

five7kid

iTrader: (14)

But only 3 of those go into the tunnel. The 4th one in the tunnel is the rear brake line.

InfernalVortex

iTrader: (4)

The fourth fuel line goes to the little vent above the rear axle doesnt it?

bradley23150

iTrader: (10)

Yes.

Also-
The vapor canister line extends further toward the front of the car than all the others.

meso5012

I'm really confused...How do you know how to tell them apart if they are all the same size... mine are all chopped off. I was going to do my fuel lines under the hood this weekend but don't how well that will go after readin this thread.

//<86TA>\\

iTrader: (15)

but they are NOT the same size, one is 3/8 od, one is 5/16 od and the other is 1/4. VERY easy to tell them apart......

patricklav

iTrader: (7)

Sorry for bringing back an old thread but wanted to confirm that this is how i should route my new lines.

3/8 - supply
5/16 - return
1/4 - evap can

thanks

bestracing

That is correct

Also just FYI if you are using AN fittings:
3/8" = AN-6 fittings
1/4" = AN-4 fittings

patricklav

iTrader: (7)

thank you

audioc

i'm taking off my smog stuff. Can i just remove the evap/and return fuel lines?

bestracing

The removal of the return line really depends on what type of fuel system you have. If it's an EFI system or the stock style mechanical fuel pump then definitely NO!

Some aftermarket electric fuel pumps that are for carb'ed motors can be run without a return but using a by-pass regulator and return line makes it easier on your pump. Same can be said about mechanical fuel pumps that are single feed in and single supply. Those will work without a by-pass regulator and return line as well.

audioc

Kind of what i thought on the return line. What about the line coming out of the evap to the tank on the drivers side of the engine?

bestracing

That line in combination with the vent line in the rear keeps the tank from building too much pressure or from forming too much vacuum in the tank. The vent in the back only allows air in and the part to the canister draws the vapor/pressure off the tank and delivers it to the motor to burn it off. It would be wise not to fully cap it off, see what racers have to do to vent their fuel cells properly. This is what you are really trying to do anyway.

WickedBowtie

Can someone chime in and tell me which line is which. Thanks.