You're being pulled in too many different directions from lots of misinformation. As you have probably figured out by now, throwing random parts at a problem is the most expensive and least effective way to diagnose this type of problem. It would cost a lot less to have it professionally diagnosed and repaired.
Your observation of no spark when you have a crank / no-start condition is one of the places we start, but what gets most people derailed is your incorrect conclusion the fuel system is working. It sounds like you based that on the hum you hear of the pump when you turn on the ignition switch. That is a valid observation that the pump is working, but that's all. The Engine Computer turns on the automatic shutdown, (ASD) relay for one second when you turn on the ignition switch. That relay sends current to the ignition coil pack, injectors, alternator field, oxygen sensor heaters, and the fuel pump or fuel pump relay. One of the initial tests is to see if the ASD relay is being turned on for that first one second, and we have verified that already by hearing the fuel pump.
Next, the computer turns the ASD relay on again whenever it sees engine rotation, (cranking or running). It knows that by the signal pulses it receives from the crankshaft position sensor and the camshaft position sensor. If either signal is missing, the ASD relay remains off, so you'll have no spark, no injector pulses, and the fuel pump will not be running. If you were to connect a fuel pressure gauge to the test port, you'd find it is near normal, but that is due to it running for that initial one second. That is done to insure fuel pressure is up for starting in case it bled down over days or weeks. Way too many people get hung up on the first thing they find missing, which is usually spark, and they forget to look for other related clues. In this case fuel pressure is hard to check because we would need to listen for the hum of the pump while cranking the engine. If we could do that, we'd find the pump is not running during cranking. Fuel pressure remains normal because the injectors are also not pulsing, so no fuel is leaving the fuel supply system or entering the engine.
Less than two percent of these crank / no-start conditions are caused by the ignition system. Even if an ignition coil were to fail, only two cylinders would be dead. The engine would still run on the other four cylinders. There's also three different ignition coil driver circuits inside the Engine Computer, and failure of all three at the same time is very unlikely.
About three percent of crank / no-starts are caused by the fuel pump. The first clue is you won't hear it hum for the one second when you turn on the ignition switch. The next clues are you won't have fuel pressure and you will have spark. GM fuel pumps almost always start up, then they fail while you're driving, leaving you sitting on the side of the road. Chrysler pumps fail in just the opposite way. They almost always fail to start up, leaving you sitting in the driveway or parking lot. Once they do start up, it is extremely uncommon for them to fail while you're driving. For that reason, when you have a stalling-while-driving problem, the fuel pump wiring and connector terminals are valid suspects, but the pump itself is way down at the bottom of the list. As a point of interest, when you do have a Chrysler fuel pump that fails to start up, there's a real good chance you can get it started by banging on the bottom of the gas tank. If that doesn't work, bang on it while a helper is cranking the engine. This failure occurs from worn brushes in the pump's motor. It takes just a little vibration to get it started, then it will remain running until you stop the engine. This failure to start up could occur the next time you try to start the engine, or it might not act up again for months, but that is the clue the pump will need to be replaced in the near future.
A good 95 percent of these crank / no-starts are caused by a failing crankshaft position sensor or camshaft position sensor. To add to the misery, they often fail by becoming heat-sensitive on all brands of cars. One common set of symptoms is the engine runs fine as long as you're driving. Natural air flow keeps them cool. When you stop for a short time with a hot engine, as in when stopping for gas, "hot soak" is when engine heat migrates up to the sensors and causes one to fail. In most cases the sensor will work again after cooling down for about an hour.
The place where mechanics will start is by reading and recording the diagnostic fault codes, but that isn't going to work here. By disconnecting the battery or running it dead, the fault codes were erased and that valuable information was lost. The second problem is it is common for no fault code to set related to these two sensors just from cranking the engine. The computer needs more time to detect the defective condition, as in when a stalled engine is coasting to a stop. For that reason, we can never assume both sensors are working just because no fault code has been set for one of them.
What we're left with is we know the fuel pump is capable of running, there's no spark, fuel pressure isn't dropping so we know the injectors aren't pulsing, and there's no fault codes to direct us to the circuit that needs to be diagnosed. Now we have to do the testing the computer would normally do on its own. Specifically, we need to know if the ASD relay is being turned on. You can do that with a voltmeter, but a test light is more effective for this type of problem. If you need it, here's a link to an article on how to use a test light:
https://www.2carpros.com/articles/how-to-use-a-test-light-circuit-tester
If you don't have one, you can find a perfectly fine one at Harbor Freight Tools, Walmart, or any hardware store. This needs to be an inexpensive test light with a standard incandescent bulb inside, not one of the new fancy ones with LEDs or electronics inside.
Look for the wire that is the same color at every injector and at the ignition coil pack. On most Chrysler models, that will be a dark green / orange wire, meaning dark green with an orange tracer, (stripe). Back-probe through the rubber seal alongside that wire at any of those locations with the test light's probe. If the test light never turns on, most likely the probe isn't touching the terminal. Wiggle it or move the light around until it does work.
If you can't see the test light from inside the van, have a helper run the ignition switch while you watch it from under the hood. It is going to light up for one second when the ignition switch is turned on. We know that because the fuel pump turns on for one second. It is on this same circuit. What is important is whether the light turns back on during cranking. My guess is will not when the crank / no-start condition is occurring. That would point to a failed crankshaft position sensor or camshaft position sensor.
At this point a scanner is needed to see what the Engine Computer is seeing and responding to. I have a Chrysler DRB3 for all of my vehicles, but most aftermarket scanners should have a similar means of showing the state of these two sensors. Mine lists each one, during cranking, with a "Present" or "No" to indicate if the computer is seeing their signals. When one of them remains at "No", that is the circuit that needs to be diagnosed.
You can try to see if the computer has detected a missing signal by reading the fault codes yourself, but remember, an absence of fault codes related to these sensors does not mean they're both working. The only conclusion we can draw is if a fault code did set for one of them, that will tell us where to look.
Chrysler made reading fault codes in the Engine Computer yourself much easier than any other manufacturer. Cycle the ignition switch from "off" to "run" three times within five seconds without cranking the engine, leave it in "run", then watch the code numbers appear in the odometer display. You can go here:
https://www.2carpros.com/trouble_codes/obd2/p0300
to see the definitions, or I can interpret them for you. If you do get a fault code for one of these sensors, the next thing to be aware of is no fault code on any brand of car ever says to replace a part or that one is bad. They only indicate the circuit or system that needs further diagnosis, or the unacceptable operating condition. When a sensor or other part is referenced in a fault code, it is actually the cause of that code about half of the time. First we have to rule out wiring and connector terminal problems, and mechanical problems associated with that part. Once all those other possible causes are ruled out, it is acceptable to spend our customer's money on the part.
Scanners are expensive, and it only pays to buy one if you're going to have plenty of use for it. Considering the age of your van, a good option is to look on eBay for an out-of-date Snapon Solus Edge. You can find a Chrysler DRB3 there too, but those went obsolete starting with 2004 Dakotas and Durangos, and on every model by 2008. With an extra plug-in card, these can do emissions-related stuff on all brands of cars sold in the U.S. starting with '96 models. For that reason, a lot of independent repair shops bought them. Since they have little use now at those shops, you might find one at a local shop that they'd be happy to sell so they can invest in something newer.
The problem with Snapon's scanners is they charge an extremely high fee to update them each year, and you can't skip any years. If you find one on Ebay that is updated through 2014, for example, you would have to pay $1000.00 for the 2015 update before you could buy the 2016 update for another $1000.00, then you can buy the 2017 update, then the 2018 update, all for another $1000.00 each. I bought mine updated through 2018 to use on my 2014 Ram, but I'm not going to buy any annual updates to keep it current. Instead, it would be less expensive to just buy a brand new one with the latest updates, for around $4000.00. The reason I'm bringing this up is it works to your advantage. Since it's less expensive to buy a new scanner than it is to update an old one, they lose their value to the independent repair shops that need them to work on the latest car models. For that reason, you can often find these on eBay for $500.00 to $800.00.
When you don't have access to a scanner, you're limited to reading fault codes, or using voltage tests to diagnose the problem. We never approve of throwing random parts at a problem, but this is one tine when it might make sense to replace a sensor, then see if the problem occurs again. I'd start with the crankshaft position sensor. It's at the back of the engine in the transmission's bell housing.
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Tuesday, March 10th, 2020 AT 3:57 PM
