'83 Spider won't start

I finally broke down and sold my 83 Spider to a friend of mine. He
came over to get it today and wouldn't you know the beast won't start.

Three of us spent the better part of the day trying every trick in the
book just to get the engine to kick over but we got nowhere.

When I crank, the motor just turns at a constant rate. It never seems
to catch at all. It doesn't stumble or speed up. It's like there is
no power stroke. This makes no sense to me since I know it's getting
fuel, air, and spark.

The battery is fully charged. It's plugged to the wall with a
charger. It turns over a little slow but it has always turned over
slow. I've actually been using the starter motor to move the car in
and out of the garage so I think it's cranking fine.

The spark plugs are all firing. I've pulled every one and checked
them against the block. There's a clean strong spark. I replaced
them all with new Bosch plugs anyway. They are properly gapped and
they all spark fine too.

The rotor and cap were kind of old. There's evidence of arcing in the
cap. I replaced both of them. It didn't help a bit.

I crudely checked the timing by putting the number one cylinder to TDC
compression and verified the rotor points to the number one point.

The wires are in decent shape. There's no evidence of arcing from the
wires. No spark flashes at night.

It's been a bit rainy but the car is quite dry now. I'm in San Diego
and the temperature reached about 65 today.

I can hear the fuel pump run when I turn on the key. I pulled the
fuel line, ran it to a jar and saw plenty of fuel come out when
cranking. I sprayed starter fluid in the intake and even into the
cylinders and it doesn't seem to react at all.

I can feel air being pulled into the intake and exhaust coming out the
pipe. There doesn't seem to be any vacuum leak.

The timing chain isn't broken and I can see the valves move.

I don't have a compression tester, timing light, or fuel pressure
gauge. However, the fuel is certainly being delivered. The plugs are
wet. The timing is electronic and roughly correct. I don't see how I
could have suddenly lost compression on all four cylinders.

I believe this all started because I ran it low on gas. I've since
added two gallons of premium from a gas can. I don't drive the car
much so I'm guessing it got some pretty cruddy fuel when it reached
the bottom of the tank. However, I'd think that's well been cleared
out by now. I'm still amazed that it doesn't respond to starter
fluid.

Anybody have any ideas?