The fuel return line on my car has seen better days.
The feed line is new.

I fired the car up with the pump return hose disconnected, to note just how much psi it pushes when open.
Sprayed right into the bucket in a steady pee stream.

I know some of the older models came with pumps with no return provision.

So.... my question is:
If I block off the return line on this pump, will it eventually hurt the diaphragm?
Will the carb then get too much psi and affect the float?

I'm not sure if the ones with the return line are higher volume diaphragms or not.

Please advise. I know this motor can handle the extra fuel since it's a big block around 400 horse, just wondering if it will throw off my settings, or is just taking the path of less resistance.

 

If you block off the return line I believe you will have to install a vented gas cap

 

Hmm. I would think it could breathe plenty of air from the charcoal canister line, but perhaps not.

Just trying to get a better idea of how the fuel system operates, and looking to optimize it for a good balance with the combo.

 

You can run a mechanical diaphram pump with the return line plugged, as these unit's are only designed to pump at 5 psi, with the return line only being a tiny orifice. Reason for the return line, is constantly circulating fuel through the main feed line to keep it cooler. If running on really hot days, especially stuck in traffic, return lines a good idea.

 

I'm afraid you're confusing the fuel return line with the evaporative cannister line. Yes, you can plug the return line (both sides) and the car will run fine, so long as you don't get percolation.

 

Well, I trimmed, and ran a tap into the pump's return line feed, and put a fine thread bolt in it......still leaked, just a drop or so every minute or 2......
so I just manned up, rolled under it, and bent a new return line.

No sense 1/2 assing things when flammable liquids are involved.

 

X2. By the way, straight threads are not designed to seal, thus your leak. On the other hand, all you need to do is put a short length of hose on the fuel return port on the pump and plug the end of that hose.

 

The return output from the pump is either female NPT or inverted flare. You can get a male plug to seal it.

 

Not on ones I've seen - They're all smooth hose barbs. The output to the carb. is a flare. May be a year difference, though - I'm talking '60's / early '70's.

- Eric

 

You're probably right on the OEM pump. What year is the car?