On a 1987 25th anniversary edition camaro with a 305, which of the fuel lines on the fuel pump are the feed and return lines?? I'm reconnecting all of them to a different fuel pump but don't know which lines are which. Thanks.

 

On my 1989 Camaro 305 FI Vin E (TBI) I have this arrangement:

If you look down on the fuel pump assembly from the rear of the car the 4 metal tubes on my Camaro are:
(going from passenger side to driver side ** ):

- 'Fuel' feed to the carburetor (with pressure in fuel injected cars)
- 'Return fuel' from carburetor fuel regulator going to the fuel tank
- 'Fuel vapor' directing vapors to the Vapor Storage Canister in the front of the car. In my car on the driver's side near the headlight.
- 'Ventilator' hose from the Ventilator Assembly located in front of the fuel tank (small white one-way valve hanging down off the end of a rubber hose).

** But you should trace these lines on your car in case they differ from mine for some reason.

 

the method of induction is needed for an accurate response. IIRC, they had carbed, TPI ,and TBI that year on 305's, different systems = different answers.

 

This may be an old post that i searched for.. but awesome answer, just what i was looking for, Thanks.

If i can add in a few questions- the vapor storage canister, is that 100% needed, or can i block that off and just run the vapor valve by the tank. I am going from my fuel injected v6 to a 1st gen 350 carburated. I switched out the fuel pickup assembly to the carb 305 one.

I do not have the vapor storage canister ( i think) i may still have the one from the v6, but can i use that if i do have it? If not like i asked, can i block it off?

Is there anything else that attaches to the canister or is it just that 1 line going to the tank?

Thanks

 

Sorry for asking, got my questions answered doing some more searching. Really good thread if you guys havnt read it..

https://www.thirdgen.org/forums/tech...-canister.html

 

However my question about if the v6 fuel injected and the v8 carburated canisters are the same?

What do they look like?
Any advantages by not using the canister and using a vented cap in place of it?


And last one, where does the return line hook up to exactly on the carb?
Thanks

 

My '86 Silverado 305 has only one line going to the carb, no return.

AFAIK a carb doesn't use enough pressure to require a return line. You would definitely need one and a regulator if you're using a high pressure fuel pump otherwise the pressure would over power the float valve in the fuel bowl and flood the intake.

 

There's no return line to the carb, there's a return line to the carburetor's fuel pump.

 

Is pressure to the fuel pump internally or externally regulated?

 

Pressure in the carburetor feed line is regulated internally by the pump.

 

so im a little confused here.. I dont need the return line?
I have no electric pump.. Its the mechanical pump that is on the lower left side of the engine block.
So i can block off the return line then?
An i can block off the vapor canister line and just get a vented gas cap?
Only thing i would need to do is run my main fuel line to the pump on the engine, then from there to the carb, and i would need to buy the ventilator valve that sits by the gas tank area

Do i have this all correct?

If so, where would i buy one of those ventilator valves?

 

If the mechanical pump has a return fitting on it, you must connect it to the return line.

You can block the vapour line if you have some other means of venting the tank. Some people just put a small fuel filter on the end of the vapour line as the vent.

 

What i have is the pump at the bottom of the block with a hole to thread in a fuel line and a nipple fitting on the other side of that pump. Where do i run the line from my gas tank? What i thought is line from the gas tank to the nipple fitting on the pump and then the threaded part of pump from there to the carb? do i have this wrong?

also the ventilator valve, where do i get one of those?
Thanks

 

The threaded fitting on the pump is the output to the carb, the hose barb is the input from the fuel line. No return line on that one.

What ventilator valve do you mean?

 

its the small white ball looking vent that is on the bottom of the car by the gas tank.

Not the Vapor canister in the engine bay.

Its close to the tank, just hooks to a bracket. What is its purpose? I am assuming i need that if i am going to block the vapor canister line and put in a vented gas cap.

 

I take that back. tell me if this sounds right. I would block the ventilator valve line since the car came with a completely blocked gas cap, and then replace it with a vented cap, that allows air in when needed, but does not allow air out.... Block the return line since it is not needed, and put a filter on the line that went to the canister.

If this is right and i would use a filter. Where would i mount it so it is out of the way of spark and heat.. is this safe or a ticking time bomb?

 

It's called a "remote pressure/vacuum relief valve."

I don't see the need for a vented cap if it already has this valve on it.

 

The relief valve only lets air into the tank as the fuel level drops, you still need to allow for vapour to escape with increases in temperature.

 

Well now that confuses me, why call it a "pressure/vacuum" relief valve if it only relieves vacuum? By its nomenclature it should relieve both.
TSB #88-298-6E states that the use of an in-tank pressure relief valve was terminated and replaced with an under hood valve (on vapor recovery system.)

The one over the axle is probably a back up for both pressures.

 

The in-tank valve is something different. It was on the sending unit inside the tank and kept the vapour line closed when tank pressure was low. It also incorporated a rollover valve to close the feed lines when the sender inverted.

 

I hate to keep this going, but i am still confused.

Should i block everything off except the main feed and put on a vented cap? Is this a 2 way or just 1 way.

Or should i buy a new canister and new ventilator valve and put those on.

Id rather not get those because i like the clean look of my engine bay without the canister.

But by using the vented cap, will it smell very bad? If not, what would i do to go this route