I forgot to mention, because it is a tight fit in the fuel filter/pump area, you might want to loosen the alternator, remove the drive belt(s) from pulley and pull to the side, then tilt alternator up and out of the way. That might be helpful, if you can’t see the area or got big hands.
Chrysler has two official fuel pump tests, Vacuum and pressure.
Vacuum (on line coming from tank) should be between 11” to 22” of vacuum.
I have removed a lot of fuel pumps in my life and have never ran a vacuum test (yet).
Fuel pressure test results should be 5.75 to 7.25 PSI.
I don’t like pressure tests because of leaks, finding the correct fittings and so forth – it just takes time to perform.
No other recommended test results from Chrysler.
My recommended test is the fuel volume test.
Just disconnect the fuel filter, get a piece of hose, 1.5 to 2 foot, maybe, attach to the fuel pump side of fuel filter (filter should be removed at this point). There is no official spec - but a pint of fuel every 30 seconds of cranking is about right.
The fuel volume test is the fastest, easiest one and tells me more than any other test I know of.
Note: the small hose from fuel filter sends the excessive fuel (what carburetor doesn’t need) and sends it back to the fuel tank. This does remove a ton of vapor lock problems.
In your container, the one you used for fuel volume test, you should be able to see any contaminates (dirt, rubber, etc.) or water (which settles to bottom and will separate from fuel (which floats and has a slight tint in color to it).
Other than displacing the air in your temporary fuel hose – there should not be any air bubbles in the fuel. Most rubber hoses crack over time and it is easier to suck air and to suck a liquid (what AJ/FormS said).
My diesel pickup has a bad problem with the fuel return hose cracking and diesel running back to the tank. The problem is without fuel in that return hose, the mechanical fuel injection pump can’t build pressure. It makes no logical sense, and just about all hard starting concerns are fixed by replacing both hoses (both are generally cracked).
Our cars are not sensitive to fuel return line leaks, matter of fact, you can get a 5/16” 2 line filter and just not hook anything up to the fuel return line and will be fine. Personally, I would use the 3 line filter because it does help with vapor lock issues.
Tires, radiator/heater hoses, fan belts, just about anything rubber will wear out in the elements. FMJ fuel hoses will crack over time and generally will leak air, not fuel (contrary to belief), unless you park at a steep angle with a full tank (then you can experience fuel leakage).
Most FMJ cars also has a hidden fuel hose that is hard to get to. You have to remove the Right Front tire to get to it. It is on top of the frame rail where it meets the firewall. That short piece of hose (about the length of fuel filter hose) has caused more than one mechanic to lose hair over it.
The pictures below is hard to see (the best copy I have) and it is the Red Circle in picture.
Expanded view of picture above.
Another expanded view of picture above.
This is from my ’82 parts book and should be the same as your ’80 Cordoba.
BudW
Edit: Another possibility is a rusted hole (or physical damage) to the fuel line somewhere.