Let’s see what I can remember. The spring was about 3 or 4 inches long, made of wire about 3/16-in dia. Pretty plain coil spring; open ends. It fit horizontally betweeen the door jamb and an arm of the hinge. There was a little bump on the hinge arm to retain the spring, and I guess there was a bump fitted to the door jamb, too.
The most appropriate tool I had was my Craftsman channel-lock pliers. I can’t remember if they would even open wide enough to get the whole spring. Maybe I wedged one or both jaw tips in between some of the spring coils. Squeezing the channel-locks with all my might, huffing and puffing, would compress the spring enough to fit in. But you could not just put it in. Memory is fuzzy. Maybe the channel-locks could not fit into the space. Or maybe it was that the spring kept popping out of the pliers’ jaws (the jaws had to be on the edge of the coil end, to let the coil fit onto its mounting bumps).
So I ran a piece of barely-strong-enough wire through the spring lengthwise; grunted on the channel-locks to compress the spring; and held the channel-locks with one hand while I twisted the wire ends together. The wire held the spring compressed, but only on one side, so the spring had a bit of arc. I pushed the spring pretty much into place, and cut the wire.
Do not try this at home.
I was replacing the hinge because a pin that stuck out of its top (sort of an extension of the hinge pin) had disappeared. A small-town body shop where I worked had quoted me a big-city price to replace the hinge. I went to the big salvage yard between work and home, got a hinge (same color!), and did the job myself. A few years later, fishing around the door jamb area with a magnet, looking for a dropped bolt, I recovered the missing hinge pin. Turns out, I think, that all I needed from the salvage yard was that pin, which could have been hammered out and in.
I got a lot of little pieces from that salvage yard to keep the 'Chevy – and the '87 Buick Century – happy.