Monojet carb question, accel pump

[pbjsammich]

Just picked up a 71 C10 with a 250 equipped with a 7040011 Monojet. Truck runs pretty poorly....there's a very evident missfire on idle. Stab at the throttle and it falls on it face. Slowly rev it up and it's fine. I think the points dist is showing it's age, so I have an HEI in the mail. Did the usual checks for vacuum leaks. Gas in the tank was old, so I bought a carb rebuild kit and ran into some issues:


One thing I found upon teardown was that the plunger for the accelerator pump (item 34 below) was stuck in the cylinder, off the piston. I removed the plunger from inside and installed a new plunger on the piston. Put everything back together and started it up. Ran a bit smoother this time around, but still having the same problems with stabbing at the throttle. Tore it down one more time and again, I found that the NEW plunger was off the piston. Both old and new are the blue colored plungers FYI.


The piston has a return spring located underneath, but no garter spring. Looking at the piston design, it appears a garter spring would be needed to hold this in place??

Or maybe my return spring has lost some of its gusto?

Do I need to "lube" the cup up a bit before I get some fuel in there?

Or am I missing something else here?

I'm an amateur at best when it comes to carb rebuilds. Any monojet gurus out there?