Discussion Forum - Northstar Chevelle Club

gearlube · Active Member

Can you help me identify these into my gas tank?

67ss · 1K+ Club

This is from the factory 72 service manual. Hope this helps.

gas tank vapor hoses.jpg

bowtie · Secretary

With my EFI, I had a bung welded onto the filler neck for the return and ran a separate line from the front to the back. Not sure if the evap line is sized right for the volume.

Are you running an in-tank pump or external? I have an external pump and used a sump wedge welded onto my tank. Some internal pumps (the large module style ones that also have the level sensor) have a return line port built onto them at the pump's mounting flange area.

bowtie · Secretary

That separator is located up behind your back seat.

gearlube · Active Member

Chris that helps a lot. So that hard line or vapor line must have been what connected up front into the charcoal canister. I think your right I that I cannot use the vapor insert as that is 1/4" line and I need 3/8. Does not make since to run 3/8 line to a 1/4 inlet. So since this is most likely the original tank I should just replace it. I am using an external sump pump for the efi. It's Edelbrock kit. I just need the return now because of the bypass hose. I see with most fuel sending units you can get a dual pipe, but one is 3/8 for the fuel line and one is 1/4 for a factory return line. I need to hunt for a dual 3/8.

-- Edited by gearlube on Monday 12th of May 2014 02:36:15 PM

67ss · 1K+ Club

This should do the trick, http://www.robbmcperformance.com/products/1069_gmsend.html.

67ss · 1K+ Club

http://www.rockauto.com/dbphp/x,catalog,22,partnum,GM34UFI,d,SPECTRA_PREMIUM_-_COOLING_DEPOT_GM34UFI.html

This is option 2 but I don't know if the supplied pump is up to the needs of your system.

gearlube · Active Member

I have been doing more research and it looks as though this vapor line is 5/16" to the vapor pipes to the tank. If that is the case couldn't I just use the far most right side, cap off the line, and run a 3/8" line to it? Or does the vent tube flow into the tank where it would not be good to use it?

SShink · 3K+ Club

Looking at the Edelbrock info page on the sump, wouldn't it just be easier to replace the factory charcoal canister that is missing, install it in the original location, route it to the sump, and you are done? This is dealing with vapor, not fuel flow. Here is one from Summit for $45: http://www.summitracing.com/parts/smp-cp3121/overview/

FUEL TANK

VENT TUBE (90° QUICK CONNECT)

ROUTE TO CHARCOAL CANISTER,

FUEL TANK VENT

(if equipped)

,

or BACK TO THE FUEL TANK

(fuel tank must have a vent or use a vented cap)

gearlube · Active Member

Stan that is the fuel vapor. Not concerned about that. But thanks for checking on that. Talking about the fuel line return. I think I will just leave the vapor lines alone and use the 1/2" sending line unit. I can run 1/2 fuel line hose off both lines. Then use a coupler "reducer" from the 1/2" to 3/8" on the hose. That will make the system happy as the last foot or so will only be 1/2. Better to go from smaller to bigger, then bigger to smaller. We're dealing with low pressure anyways.

-- Edited by gearlube on Monday 12th of May 2014 05:18:18 PM

SShink · 3K+ Club

The Edelbrock sump kit doesn't use a fuel return line from what I see. That's the whole thing about it. Are you doing something different, or not using that sump?

gearlube · Active Member

Sorry let me give you the back story. I got the sump for ease of use with the pump etc and the lines. Problem is that the sumps come in fixed at 49lb or 66lb. I went with the 49. I am having a few issues with my quick fuel efi. Working with their tech support they told me I had to get my pressure down to 42lb because that where their settings are mapped to. Right now my gauge is reading 50-51. The quickfuel kit came with a fuel regulator. The only way they said to regulate that pressure down was to hook a return line from the bottom port of the regulator and run a return line back to the tank so I can throttle the pressure down. I did not see any inline fuel regulators that will operate at those pressures. I should have done more research first on that.

So I am going to buy the 1/2 fuel sending unit. Run the 1/2" hose to the inlets and then use a reducer to the existing fuel line and splice it in. Then from the regulator I will run 3/8" hose all the way back to the second inlet splicing in another 3/8 to 1/2 reducer to return the fuel back. Once hooked up I should be able to dial down the regulator to 42lb.

Their fan relay is not working either. Set in the computer to come on at 180 degrees. Never turns on. Dialed it down to 120 degrees and put a test line on the fan wire. Should see 12V better nothin. They are looking into that one....

Fun fun

-- Edited by gearlube on Monday 12th of May 2014 07:50:57 PM

dashboard · 2K+ Club

Tom, here's a couple of adjustable fuel regulators? You could mount it near the fuel tank then set the pressure with a gauge in the engine compartment at whatever the required value is.

www.summitracing.com/parts/aei-13301/overview/

www.summitracing.com/parts/aei-13129/overview/

Not sure I completely understand your dilemma, hope it helps.

Looking forward to you getting this done so we can hear the results.

-- Edited by dashboard on Monday 12th of May 2014 07:45:40 PM

gearlube · Active Member

Thanks Kevin. I have a fuel regulator that is 30-70 PSI from the QFI kit. So I am good there. The dilemma for me was how to route the return fuel line back from the regulator so I can dial back my fuel pressure. The QFI kit is on the low end for its pressure needs for a TBI. I thought the Edelbrock would be plug and play. And of course when I called their tech line they weren't too happy to help because I was not using it with their system. Right now I am putting in 50-51 LBS into the QFI when I need 42lbs and it is screwing with my AFI and my maps. I am basically running really rich. Just want to do it right the first time. QFI does not want to tweak their maps and are not a big fan of a return less style system eve though technically it isn't. I am using the Edelbrock sump, but the bypass function is built into that pump however the pump in the Edelbrock is not adjustable. Hence my dilemma. Chris P steered me towards a fix so I don't have to get a new tank/pump etc. running the return line is pretty easy. Plus I don't want to mess with the vapor lines since vapor lock is more of an important issue with EFI. I placed an order for the 1/2" sending unit.

Tank only has 1/4 tank of gas so it's perfect to drop to change out the sending unit and connect it all up.

gearlube · Active Member

Question. Since I will be putting in a 1/2 fuel sending unit, would I really gain anything bring up a 1/2 fuel line too? I doubt it since my mechanical is just feeding the sump....

Scott Parkhurst · Super Poster

Could you run a T (or a Y) fitting and split the return line into 2 smaller lines so you could use the 'extra' vents into the tank for returning fuel?

67ss · 1K+ Club

I wonder if you could put another fitting back into the sump assembly to dump return right back into itself. Not sure if it would over flow the unit or not, I don't know if it blocks the low pressure coming from the mechanical pump if level gets to high inside??

gearlube · Active Member

Scott Parkhurst wrote:
Could you run a T (or a Y) fitting and split the return line into 2 smaller lines so you could use the 'extra' vents into the tank for returning fuel?

Hi Scott,

i asked Quickfuel that and told them it's a 5/16. They want to see the 3/8" line back. I bit the bullet and got the 1/2" sending unit with dual inlets. I already spent so much on this EFI, no sense in going cheap now....

gearlube · Active Member

67ss wrote:
I wonder if you could put another fitting back into the sump assembly to dump return right back into itself. Not sure if it would over flow the unit or not, I don't know if it blocks the low pressure coming from the mechanical pump if level gets to high inside??

I asked Edelbrock about that and if I put a hole into it to customize it, I loose my warranty. Second thing is the sump is dual chambered and blocks the low pressure as you guessed from the mechanical. Like I wrote to Scott I took your first advice and got that sending unit. dropping the fuel tank is easy sine I have a lift and a trans lift to do it. Plus I think I am going to go ahead and run a 1/2 line for the fuel delivery too since those lines are original. Will be cleaner and the extra fuel inbound will mean my mechanical will always keep up with my electric side. 1/2 low pressure fuel line is pretty cheap, like 1.19$ a foot. On the fuel return I am just going to do 3/8 to the rear and then splice to 1/2" for the last foot. Really low pressure there, like 8-9lbs. Quickfuel said I have to get those pressure down before the will help me on the fine tune.