$700.00???? It's time to find a different mechanic.
Thanks to the politicians you and I voted for, there is so much government regulations, taxes, and unnecessary involvement that repair shops have to charge at least $100.00 per hour, and I don't understand how they can afford to stay in business at that rate, but there is something wrong here with that estimate. Each of those sensors should cost less than $70.00. The crankshaft position sensor is a little difficult to get to and could take an hour to replace. Keep in mind this doesn't include any diagnostic time, but just to replace the part, part and labor should be less than $200.00.
The camshaft position sensor is real easy to reach and can be replaced in a couple of minutes.
Your mechanic may have included some diagnostic time in the estimate, and he may have inflated the estimate to cover unexpected or unknown things that might not be needed. Your final bill could be a lot less than $700.00.
If the engine runs at all, as in one or two seconds, you know it has spark and fuel pressure. To stop after two seconds is what happens when the theft deterrent system kicks in. What needs to be done is to determine if the automatic shutdown (ASD) relay is turning on when the engine won't start. That can be done by measuring the voltage on the dark green / orange wire going to the ignition coil pack, any injector, or either small wire on the back of the alternator. A test light works better for this than a voltmeter because most digital voltmeters don't respond fast enough. You should see voltage on that wire for one second after turning on the ignition switch, then it will go away. You might hear the hum of the fuel pump too for that one second. Next, that voltage must come back during engine rotation, (cranking or running). When it doesn't come back and the engine never starts, that's the time to suspect the cam or crank sensor.
That voltage must go to 0 volts when the engine stops running for any reason. This can be hard to catch, but you have to see if the engine stops first, then the voltage goes to 0 volts one second later, or does that voltage go to 0 volts, then the engine stops right away.
Another approach is to read the diagnostic fault codes to see if one is set related to those sensors. Be aware that they often don't set just from cranking the engine. The sensor has to fail while you're driving, then the loss of signal will be detected as the engine coasts to a stop. These codes may not turn on the Check Engine light because they don't relate to things that could adversely affect emissions.
Chrysler makes it possible to read the fault codes yourself. Cycle the ignition switch from "off" to "run" three times within five seconds without cranking the engine, leave it in run, then count the flashes of the Check Engine light. You'll see a series of flashes for the first digit of the code, a pause, then another series of flashes for the second digit. After a longer pause, the next code, if there is one, will flash the same way. Code 55 just means it's done flashing codes.
You can go here to see what the codes mean:
You can also have the codes read at an auto parts store. Many of them do that for you for free. It's important to not disconnect the battery or let it run dead because that will erase any codes, then that valuable information will be lost. If there are no codes stored in the Engine Computer, the next step would be to connect a scanner to view live data. I use Chrysler's DRB3 scanner. A lot of independent shops have them too because with an additional plug-in card, they will work on any brand of vehicle sold in the U.S., but only for emissions-related things. That includes engine sensors. It will list the cam and crank sensors, and "no" or "present" for each one. If one of those signals is missing when the engine won't start, that is the circuit that needs further diagnosis. The sensor has about a 50 percent chance of being the cause of that code. The rest of the time it's a wiring problem related to that circuit.
What is much more common for the symptom you described is a failing fuel pump. Pumps on GM vehicles tend to fail while you're driving, so they suddenly leave you stranded on the highway. Chrysler fuel pumps almost always fail to start up, leaving you stranded in your driveway or a parking lot. The clue to a dead pump is you won't hear it hum for one second when you turn on the ignition switch. Banging on the bottom of the gas tank often gets them going, but that works best if a helper is cranking the engine at the same time. Once the pump does start running and the engine starts, it will stay running at least until you stop the engine again.
At the mileage you listed, you're probably due for the second replacement fuel pump. My '88 Grand Caravan is 25 years old and just turned 260,000 miles yesterday, and I put in the first replacement pump about two months ago. It's not common for any pump to last that long. The additional clue to a failing fuel pump is you'll still have spark when the engine doesn't start.
Saturday, January 6th, 2018 AT 1:02 PM