Not starting

The place to start is with the exact symptoms. "Nothing" does not tell us anything. There can be over sixty wires going to the engine computer. It sounds like you tested all of them when you reconnected the battery negative cable? At one point the engine cranked normally but would not start or run, then later, when it would not crank, were the lights and other electrical systems working?

When the engine did crank but not run, could that be because it was cranking too slowly? Have you considered the possibility the battery is weak and / or has corroded or loose cable connections? You might start by measuring the battery voltage when the engine is off. If it is good and fully-charged, it will be 12.6 volts. If you find closer to 12.2 volts, it is good but badly discharged. If you find 11 volts or less, it has a shorted cell and must be replaced.

If it appears the battery is good but discharged, charge it at a slow rate for an hour, then measure its voltage again. If the engine does start and run, measure the battery voltage again with it running. You must find between 13.75 and 14.75 volts. If it is low, we will need to diagnose the charging system.

What was that fault code? A real common problem was caused by the Hall Effect pickup assembly in the distributor. The symptom was the engine cranks normally but does not start or run. If you investigate further you will find there is no spark, but too many people get stuck on that and troubleshoot the wrong system. You need to look further, then you will find there also are no injector pulses. The fuel pump also does not run during cranking, so a lot of people replace the pump, but the fuel pressure can be misleading. There will be pressure because the pump still runs for one second each time the ignition switch is turned on.

Measure the voltage on the positive terminal of the ignition coil, or either smaller terminal on the back of the alternator, to see if the automatic shutdown, (ASD) relay is turning on during cranking. You should find 12 volts there for one second when you turn on the ignition switch, then it will go back to 0 volts. What is important is if that voltage comes back during engine rotation, (cranking or running). The engine computer turns the ASD relay on when it sees engine rotation, and it knows that by the signal pulses it gets from that pickup assembly in the distributor. You can use a digital voltmeter to check the voltage, but they usually respond too slowly to catch that one-second voltage pulse. A test light works better for this test.

Be aware too that these pickup assemblies, as well as the newer crankshaft position sensors and camshaft position sensors, commonly fail by becoming heat-sensitive. The engine may run fine as long as the car is moving and there is sufficient air flow to keep the sensor cool. The typical failure occurs when a hot engine is stopped for a short time, as in when filling with gas, then "hot soak" allows heat to migrate to the sensor causing it to fail. They commonly work fine again after cooling down for about an hour.

As for the cranking problem, the first clue is whether the starter relay is clicking when you turn the ignition switch to "crank". If it is not, we have to look at the ignition switch and connector terminals, and the clutch switch. If the starter relay IS clicking, that circuit is okay and we have to look at the high-current starter solenoid circuit.

If you have a thick, clear plastic ring around the ignition switch lock cylinder, there are two things to consider. The first is overheated connector terminals. The switch must be replaced for that, then the two blackened terminals and four" of their wires must be replaced separately. That problem affects the accessory circuits like power windows, radio, and heater fan. The people who have the most trouble with this are those who run the fan on the highest speed a lot, and especially those who turn the ignition switch on or off when they do not turn the fan speed down first.

The second problem is a mechanical problem with the lock cylinder that prevents the switch from turning quite far enough to engage the starter circuit. The clue is everything else works normally, but the starter relay does not click. The dealer's part department has a repair kit for that. In my experience that problem has never been intermittent. A metal cam breaks, then the no-crank condition is permanent.

I mentioned previously the Hall Effect sensor was a real common problem, and every parts store will have some in stock. It is a three-inch diameter plastic disc that sits right under the distributor cap. On the newer cars they use two sensors instead that perform the same function. Those are the crankshaft position sensor and the camshaft position sensor. If no one understands the term "Hall Effect switch", just tell them you need a distributor pickup assembly. It will have a three-wire plug.

For the no-crank problem, you need to determine if the starter relay is clicking when you turn the ignition switch to "crank". Knowing that will tell us which circuit we need to troubleshoot. If you cannot hear it, have a helper place their fingers on it, then feel if it clicks when you turn the ignition switch.

Now we're back to a different symptom involving the starter. Most likely you're hearing the starter relay. That will make a single click each time you turn the ignition switch to "crank". If it's a fairly loud single clunk, that is due to worn contacts in the starter solenoid. If you have the little silver Nippendenso starter, there are repair kits for those. The clue is the starter will work eventually after you cycle the ignition switch multiple times. It will take more and more tries as time goes on. You're going to have to look and listen under the hood while a helper runs the ignition switch. You can't make observations or take test measurements from the driver's seat.

Dandy. Hope that's the solution.