Will not start

Considering the number of connections, splices, and the relay's contacts, three quarters of a volt is probably not too bad. At this point you have fuel pressure, and you have weak spark, proving the distributor pick-up assembly is working and the ASD relay is turning on. Even with weak spark there should be some kind of indication the engine is trying to fire. If the cylinders are becoming flooded, the engine won't fire on starting fluid. This leaves bad gas or the jumped timing belt. Did you check previously for fuel spray from the injector during cranking?

The next thing to do is remove number one spark plug and see if it's wet. If you installed Champion spark plugs, my experience has been that once they've been flooded, they will always misfire and cause very hard starting. They need to be replaced.

Leave that spark plug out so you can find top dead center on the compression stroke. There's a foam plug to remove on top of the transmission's bell housing, then you'll see the timing marks in there. When you have it at TDC, remove the distributor cap and see if the rotor is pointing to the terminal for that spark plug wire. If it's not, we'll need to check the cam timing.

No alarms yet in the '80s. They are especially effective at keeping owners out of their cars, particularly GM cars.

The cylinder is flooded when condensed gas coats the spark plug's electrodes. Even if the spark is able to occur, liquid gas won't burn. It has to be a vapor to burn. Even if there is vaporized gas in the cylinder, the spark won't reach it to ignite through the liquid gas. That will also prevent starting fluid from igniting.

I'm out of ideas unless there's something in the fuel. We need fuel, air, spark, compression, and correct timing, and we have all of those.

Well, what about compression? We know you won't lose that on all the cylinders suddenly, but I did see one where the camshaft broke in half, then most of the valves stopped opening and closing. You could tell that by the abnormal cranking sound. If yours sounds like there's no compression, or cranking speed is uneven, pop the valve cover off and watch if all the valves are moving.

There was a different problem where the cam sprocket was in perfect time, but the camshaft itself stopped turning. That was somewhat common on a different engine used in the Neons. I never saw that happen in a 2.2 / 2.5L.

I'm still bothered by the low voltage to the ignition coil. Check if there is a condenser connected to it. In this application it would just be for radio noise suppression, but if it is "leaky", meaning not quite shorted, it could draw the voltage down.

Another way to track this would be to use a small jumper wire to connect the two larger-diameter wires in the ASD relay's socket, then measure the voltage at various places in the circuit. You don't need to have the ignition switch on for this, and bypassing the relay just powers up the circuit like normal, but without the engine running.

Start right at the battery's posts. If it's good and fully-charged, you'll find close 12.6 volts. Now move the meter's probes from the posts to the cable clamps on them. You must find the same voltage. If it's lower, one of those connections is loose or corroded.

Next, move the negative meter probe from the battery cable to a paint-free point on the engine. The voltage still should be the same. Move the positive meter lead to the ASD relay's wires. By this time you might see the voltage drop a little, but ideally it should still be the same as when you started at the battery.

Finally. Move the positive meter lead to the positive terminal on the ignition coil. If you're seeing the same 9 volts you found originally, three volts is being dropped somewhere. Finding where is done this way by taking these voltage readings all along the circuit.

If you still have a good 12+ volts at the ignition coil, but it goes down to 9 volts when the jumper is removed from the relay socket and you're cranking the engine, the only thing left is the contacts in the ASD relay. If those are arced or corroded, you should get a nice strong spark if you put that jumper wire back on, and replacing the relay should solve that.

If there's an alarm system in the car, it is either an aftermarket product or it is something I have never seen before. The factory systems live inside the Engine Computer and the Body Computer, and Body Computers first showed up in '92 models.

The factory systems never have a "kill" or "defeat" switch as those would make the systems pointless. Anyone could steal the car and know right where that switch was located. Also, when it is on the car, there is no way to disable it.

I can elaborate more if necessary, but for those '92 and newer cars, if yours does not have the factory anti-theft system, you have to be careful when sticking in a used Engine or Body Computer. If you stick one in from a donor car that had the anti-theft system, it is going to teach the programming to the other computer as soon as the ignition switch is turned on. At that point you'll have a crank / no-start until both computers are replaced at the same time with two that do not have anti-theft programming. Once a computer learns that programming, it can't be undone, and from then on that computer will only work in a car that does have the anti-theft system.

The voltages at the ASD relay and at the ignition coil have to be the same. I suspect you're measuring at the coil while you're cranking the engine. A lower voltage then would make sense because the starter is going to draw the battery's voltage down a volt or two.

10.9 volts at the ignition coil should be enough to develop a strong enough spark.

Yes, the wires must be soldered, otherwise there will be resistance in the joints, and that will cause a drop in voltage. Also, only use heat-shrink tubing with hot-melt glue inside to cover the splices. Electrical tape will unravel into a gooey mess over time.

No external resistor is used in this system. When one is used, it is to limit current flow and reduce voltage to the coil to the voltage it is designed to operate on. Since system voltage is dropped even further when the battery is loaded down by the starter motor, that resistor would lower the voltage to the coil too much, so it needs to be bypassed during cranking so the spark will be strong enough to ignite the fuel. There is no provision in this system to bypass a resistor during cranking.

I just noticed something while rereading the previous replies. In the photo from three replies ago where you referred to a broken oxygen sensor wire, it looks like that has a braided copper shield around the other wires. If that is what was used, that braided wire and the other wires are different and can't be soldered together. The braided wire is a shield to keep out stray magnetic interference and it is always connected to ground.

One of those other O2 sensor wires is a dark green / black for the internal heater. That's the same 12-volt circuit coming from the ASD relay that goes to the ignition coil. If that dark green / black got soldered to the ground wire, or has a stray strand of wire that is touching the ground wire, that would explain the real low voltage feeding the ignition coil. A dead short should burn open a fuse link wire by the left strut tower, but if that short isn't a perfect short, there can be enough resistance in pitted ASD relay contacts and other connector terminals to limit current low enough so that link doesn't burn open. Instead of the expected 0 volts, you might get a few volts at the coil during cranking.

Open it up and look at the wires more closely to see if there are four of them inside a braided shielding wire. Those can be rather difficult to repair. You'll need to peel the braid back far enough to expose enough wire to be spliced and soldered. Each wire has to be spliced individually, and sealed with moisture-proof heat-shrink tubing. Pull the braided shield over those wires as best you can, but don't panic if a few inches aren't covered.

I don't remember there actually being a braided shield, so if there is not, just splice the four wires the same way, then for good measure, it would be nice to seal the entire repair with a larger piece of heat-shrink tubing.

Before you splice these wires, leave them disconnected, then see what happens to the voltage at the ignition coil during cranking. If those wires were shorted before, the engine should start now. It will run without the oxygen sensor connected, but expect to see the Check Engine light turn on. You can erase the fault code later by disconnecting the battery's negative cable for a few seconds.

I don't recall ever seeing a braided shield but It kind of looked like that in your earlier photo. There isn't one in these photos. The only thing to watch for related to a crank / no-start problem is that none of these wires are shorted together or to ground.