Could I get you advice on something? My 69 was not starting after I drove it and it was surging. I was thinking the secondary jets were not getting enough fuel. I got it home and parked it. I replaced the fuel pump and filter still no gas. I pumped air into the fuel line and felt the pressure coming out of it. I also heard whistling from the cap. I just replaced the gas cap with a locking one that didn’t seat right which I think is the culprit. I put the original one on and still no gas. I put air in the air return line to the tank about 8 pounds of pressure. After a few seconds gas spit from the air return port on the pump. So I pulled the air hose off and stuck the line back on the return port. Still won’t start. I replaced the forward rubber hose on the sending and return lines near the frame rail, under the passenger side. Is this an issue with sending unit?

 

Kind of all over the map there...

Stop replacing random parts and start logically troubleshooting.

1) Does the carb squirt fuel from the accelerator pump jets when you operate the throttle? If so, your fuel delivery is working. Look elsewhere.
2) Is there spark at the plugs when you crank the engine?
3) Is the timing about right? (you can use a timing light while the engine is cranking - it doesn't need to be running)

These will tell you if the problem is fuel delivery (#1), ignition (#2), or timing chain (#3). Once you figure that out, it narrows down the potential causes.

 

I agree, need more info on what is going on at the carb.
if it squirts fuel when you move the throttle by hand it’s getting some fuel.
if it isn’t or not enough, you said surging, it could be sticking float or a particle stuck in the needle and seat blocking it from delivering enough fuel.

you would have to check for pressure at the carb by disconnecting the fuel line there and putting a temp hose with pressure gauge on and also check for flow by running the hose into a catch can. ( I am presuming since it’s not running it’s not hot but always be careful of fuel spray)

If pressure/ flow is good, something is blocking the needle and seat or your jets are plugged…

if low pressure or flow, you could have a line collapse intermittently or your sock in the tank is clogged/ coated

But as Joe said start at the delivery end and verify then work back…don’t jump in the middle….


for ref, I have done the chase…my 69 442 would almost make it through the qtr..hit about 95, and fall flat like it ran out of fuel. I went through the process, and even though I was getting delivery to the carb, I still changed out my rubber lines and sock on the sending unit in the tank…still didn’t work.
new pump…same….
finally I yanked the carb off and found the worlds smallest t piece of Teflon tape had made it past the filter, and was blocking the needle port enough that it could not refill the bowl fast enough ….
it was all good after that…lol