1996 Plymouth Neon No Crank, No Start

I'm not clear on which wire you're testing on the solenoid. Is that "braided" wire the one going into the starter motor? If you're only finding 5 volts there, that is not enough to make the starter spin, but there's a number of things to consider. First, that voltage should only be there when the solenoid is engaged. That means having a helper to turn the ignition switch to crank", or jumping the smaller solenoid wire to the larger terminal with the battery cable on it. Once the solenoid engages, and you find only five volts on the braided wire, move the positive test probe to the battery terminal on the solenoid. If you have considerably higher than 5 volts there, the solenoid has bad contacts, but it should be making a solid, loud, single clunk when it engages. If you find 5 volts, there's a bad cable or connection. That would explain the intermittent failure to crank after the engine stalled.

There's another, less-common problem that can occur with solenoids. There's actually two coils of wire in them. One goes right to ground, and the other one goes through the starter windings, THEN to ground. Once the solenoid engages and the heavy contacts turn on, battery voltage is applied to both sides of that second coil, effectively turning it off. They do that to make the current available to the starter motor. The issue is the coil going right to ground could have an intermittent connection. You'd still get full battery voltage on the smaller solenoid terminal, and you'd see around five volts on the brushes of the starter motor, which are tied to that braided wire. With only one of the two solenoid coils working, the magnetic field will not be strong enough to move the starter drive and switch the contacts on. You need both coils' magnetic fields to do that. Once the mechanical stuff has been moved into position and the contacts turn on, the "pull-in" winding is switched off, as I mentioned, to save power, and only the "hold-in" winding remains energized as long as you're in the "crank" position. The confusing part is every once in a while, when only the hold-in winding is working, it gets just strong enough to tug the solenoid plunger far enough for the contacts to turn on. In effect, you're working with half a solenoid that is normally not strong enough to make it engage, but once in a while it does anyway.

Another thing to look at are the smaller battery wires. Follow the smaller positive wire to the under-hood fuse box and be sure that is clean and tight. Follow the smaller negative wire to the body and be sure that is tight and not rusty.

When you said the lights dim when trying to crank the engine, that should not happen unless you hear the solenoid engage. When not trying to turn on the starter motor, the solenoid itself doesn't draw enough current to draw the battery's voltage down a noticeable amount. If the lights DO dim and the solenoid isn't engaging, that is evidence of a bad cable connection or a badly-frayed cable. Everyone suspects the positive cable going to the starter but don't overlook the negative cable bolted to the engine.

You're right about having no diagnostic fault codes since the battery was disconnected, but there is another issue that might be related to the stalling. Disconnecting the battery or letting it run dead causes the Engine Computer to lose its memory. Fuel trim numbers will be relearned by driving without you ever knowing it, but it also has to relearn "minimum throttle" before it will know when it must be in control of idle speed. Until that occurs, the engine may be hard to start unless you hold the accelerator down 1/4", you won't get the nice "idle flare-up" to 1500 rpm at start-up, and it will tend to stall at stop signs. To meet the conditions for the relearn to take place, drive at highway speed with the engine warmed up, then coast for at least seven seconds without touching the pedals.

It sounds like you have a bad starter motor, but lets do a couple more tests. You have your meter probe on the battery's negative post. The other probe is on the braided wire that goes into the starter motor, and you have good voltage up to that point when the solenoid is engaged. You should be hearing a rather aggressive clunk when it engages. At that point, with 12 volts on the braided wire, the motor should be spinning, but we have to check the ground return too.

Move the positive meter probe to the case of the starter or an unpainted point on the engine block. If you find any voltage there, the problem is in the negative battery cable. Actually, you're allowed up to 0.4 volts there during starter engagement, but if you have a cable problem, it will be pretty obvious. The voltage will be much higher than 0.4 volts.

If you can get it to act up long enough, check for spark. Chances are it will be missing. The main suspect will be the camshaft position sensor. Next will be the crankshaft position sensor. The Engine Computer needs to see engine rotation, (cranking or running), then it turns on the automatic shutdown (ASD) relay. That relay sends current to the ignition coil pack, injectors, alternator field, and fuel pump or pump relay. It's the signals from those two sensors, and they must be in sync, that tells the computer the engine is rotating. It is fairly common for those sensors to fail by becoming heat-sensitive, then they work again after they cool down, but that typically takes from a half hour to an hour. A sensor could just be intermittent and cause the symptoms you're having, but corroded connector terminals would also be a good suspect.

The goal now is to get a diagnostic fault code to set related to the stalling problem. That often doesn't happen for these two sensors. It takes time for the computer to decide to set a code once it sees all the right conditions, and that can occur in the time it takes for the stalled car to coast to a stop. After that, and since disconnecting the battery erased any codes, they may not set again from just cranking the engine. This is where you need a scanner. I have a Chrysler DRB3 because all of my many vehicles are Chrysler products. Under "Sensor Data", it lists those two sensors with "Present" or "No" to tell you if it's seeing those signals. I have a DRB2 also but I can't remember if that shows those sensors that way too. You can find DRB2s on eBay for less than a hundred dollars, but I don't think they will work on '96 models. They use a cartridge specific to a group of models, and those only went up to '94 models. '95 models used the '94 cartridge.

The DRB3 doesn't use cartridges, but if you add a plug-in card so it will work on vehicles back to '94 models, that "SuperCard 2" also lets you do emissions-related testing on any car brand sold in the U.S, '96 and newer models. A lot of independent shops bought them for that reason. This scanner was phased out on different models between about 2004 through 2008, as I recall. Along with that, some of the aftermarket stuff is catching up to what the manufacturer's equipment does, so there will likely be a lot of DRB3 showing up on eBay. I sold three of them there years ago to pay for the fourth one that I kept.

Without a scanner you have no way of seeing what the Engine Computer is seeing or doing. If you're going to be working on this car a lot yourself, buying a used one will cost less in the long run compared to running to a repair shop multiple times. There are some good aftermarket scanners too, but I'm not real familiar with using them or knowing what's good and what isn't. Watch out for the simple code readers. Those sell new for less than a hundred dollars. They don't do much more than what you can do by cycling the ignition switch. No other manufacturer makes reading codes yourself as easy as Chrysler, so code readers have more value to those other people.

Getting back to those sensors, most scanners have a record feature that is useful for finding intermittent problems like you're having. Often a signal drops out from a sensor momentarily and you can see it switch from "present" to "no", and back again while you're driving, but scanners update their displays much slower than the speed at which the computers on the car talk back and forth to each other. A dropout is real easy to miss. With the record feature, you press the "record" button when the hiccup occurs. Since the data travels through the scanner's memory, the recording actually starts a couple of seconds before you pressed the button. Later, you can replay that data slowly to see what changed when the problem occurred. There can be an input sensor problem, as in a signal dropping out from the cam or crank sensor, or you might see an output problem related to what happened as a result of the cause. As an example, the camshaft position sensor signal is an input that could be found to be dropping out, or the ASD relay could be turning off because the computer did that in response to that loss of signal. For my cars, there's almost 40 things to look at related to information the computer is acting on.

The other benefit of a scanner is when there are no fault codes being set. Without retyping all the theory I just posted for someone else, I can sum up my novel by saying a throttle position sensor, for example, has mechanical stops inside it that limit its range of signal voltage from 0.5 to 4.5 volts. Voltages outside that range, (usually caused by wiring problems, not sensor problems), are what sets a diagnostic fault code. However, if the voltage reported is wrong but within that acceptable range, no code will be set, but a tenth of a volt error can have a noticeable effect on engine performance. Now, this is rare for a throttle position sensor to do that, but it serves to illustrate my sad story.

With a little experience, you will start to see things that aren't right. For example, if the engine has been off all day, and it's 60 degrees outside, you know there's a problem with the coolant temperature sensor if it's reporting 10 degrees. Ten degrees is a valid value even though it is wrong, and the computer will tweak its fuel metering calculations based on that incorrect information. No fault code would be set related to the coolant temperature sensor because 10 degrees is a valid number, but you might get a fault code for "running rich too long" due to the extra fuel the computer is asking for. "Running rich too long" or "lean too long" is the only information you'll get from those codes. It's up to you to figure out why, and there's little chance of doing that without a scanner.

As a final thought, a lot of auto parts stores rent or borrow tools, and they might have a scanner you can use. If you like it, you can buy one like it. If possible, try a few different brands to see which one is easiest to navigate and figure out.