Help! Fuel Pump Questions

[Corvettekid85]

I just got my hood opened on my 75 after sitting in my back yard for a few years. Ive replaced a few things and did a tune up, but now im having some problems. The Fuel pump I pulled off only had 2 lines coming off of it. I replaced the pump because the carb wasn't getting any fuel so I bought a new one and this one has 3 lines that would come off of it. I know that there's an inlet line that goes into the pump and one that comes out, or a breather line, then I have the line that goes from the pump to the carb. I was to interested in getting my old fuel pump off and putting the new one on that i didnt pay attention to what lines went where because the inner diameter of the lines are different so i figured i wouldn't have to worry about it. Now when I got underneath the car i discovered that there was a small like about 6 inches long that had a bolt in it like it was capped off. Now my old pump only had two lines coming off of it, so do I need to cap off the return hard line that comes from the tank thats supposed to go to the fuel pump? Ive hooked up all of the lines how they should be and it seems like im not getting enough pressure to pump the fuel into the pump or I have some lines mixed up. The picture im adding is what my new pump looks like. Thanks!!!

 

[Vettehead Mikey]

Sounds like who ever last worked on your car downgraded it with a 2 port pump then blocked the unused line with a bolt. Bubba is everywhere. :eyerole

The small diameter line is a return/bypass to help prevent vapour lock. The larger line is the inlet from the gas tank. I'd suggest using the correct pre-molded fuel lines as the standard lines tend to kink.

 

[Corvettekid85]

So how should I hook up the lines? I used a clear tube and sucked in and fuel was coming out of the smaller diameter line, but if i sucked on the larger diameter, nothing was coming up. So I should put the larger diameter tube into the IN tube on the pump and put the small line on the return tube off the pump? And the larger one is for the line to the carb correct? Thanks for the quick reply!! I just started a tune up because Ive been trying for years to open the hood because my hood latch was broken so I couldn't open it and my latches were rusted.

 

[Antz81]

So how should I hook up the lines? I used a clear tube and sucked in and fuel was coming out of the smaller diameter line, but if i sucked on the larger diameter, nothing was coming up. So I should put the larger diameter tube into the IN tube on the pump and put the small line on the return tube off the pump? And the larger one is for the line to the carb correct? Thanks for the quick reply!! I just started a tune up because Ive been trying for years to open the hood because my hood latch was broken so I couldn't open it and my latches were rusted.

Yes the larger line goes to the in on the pump and the smaller to the return. The carb gets connected to the remaining line.
as mike said make sure you use the pre-moulded lines as others will kink where they have to bend. (I had to replace the lines a previous owner put on for this very reason)

 

[Corvettekid85]

Ok I think I might have bought a bad fuel pump because I feel like I'm not getting enough back pressure.

 

[Antz81]

Ok I think I might have bought a bad fuel pump because I feel like I'm not getting enough back pressure.

Are you talking about in the return line to the tank?
I did just notice something else from your last post. You said you couldn't suck fuel from the tank on the larger line. how much fuel was in the tank?
I had about 1/2 a tank when I did mine and fuel flowed freely. (ccouldn't get it to stop)