Carburetor trouble.

Pressure is determined by the strength of the spring in the pump that pushes on the diaphragm. It can't put out more than what that spring was designed for. The only exception I can think of is if there is a third fitting for a vapor return line from the pump to the tank, perhaps that line is kinked or plugged.

Sorry for the misinformation. I see you have an electric pump. Is that a universal pump or one made for your truck? A lot of universal ones are meant for throttle body fuel injection systems which run close to 15 psi. Carburetors need less than 5 psi or the pressure will push the needle valve open.

Autozone and other parts store have regulators (less than $15).

Read your paperwork for proper pressure for new carb. This thing has a dial, you push it down and rotate to the desired pressure.

Most, like mine have inserts for various size fuel line. Some are plastic, some are metal. You can buy brass n. Ipples, to take the place of plastic (I had plastic ones break on me)

Make sure you sorta tie the lines down (zip ties, etc), so this does not vibrate unnecessarily

I also installed a MINI fuel pressure gauge, as to monitor whats coming thru (while it's running). I trust my Mini gauge more than the numbers stamped on the regulator.

Mini gauge also impresses everybody too. You can get a special "Tee" to screw it into, to keep it close to the line.

Ex: Reg set to 4-1/2 PSI, gauge reading "Desired" 5 PSI (Engine running)--Just an example! These are not designed for "NASA" to use, at these prices!

I have a '77 CJ 5, 258 6 cyl

Here's some pics of mine.

My OEM fuel filter splits fuel one line to the carb and the other returns back to the tank (additional overpressure protection, sorta really filters the fuel over and over too!)

Let me know if this helps or you need more info.

The Medic