Hi susanbmk. Welcome to the forum. You need to use punctuation, otherwise your story can be read three different ways. As near as I can tell, the engine will not start now but I'm guessing it cranks ok. The first thing to do is check for spark. There are actually three different systems that can cause a no-start condition. One is the fuel supply system. Unlike GM cars and trucks, it is very uncommon for a Chrysler fuel pump to quit running while you're driving. It's more common for them to fail to start up. The second system is the ignition system / spark plugs. While a problem in that system is possible, it isn't common either.
The most causes of a no-start condition are found in the trigger circuit which is common to both the fuel supply and ignition systems. When there's a failure in that circuit, the fuel pump will not turn on AND there will be no spark. There are two sensors in the trigger circuit. There's a crankshaft position sensor and a camshaft position sensor. It is fairly common for these sensors to fail by becoming heat-sensitive. That causes them to fail after the engine warms up, and it will restart about an hour later after it cools down.
Normally the Engine Computer will memorize a diagnostic fault code indicating which circuit has a problem. That code will be erased and the valuable information will be lost if the battery is disconnected or run dead. If that happens, it may set the code again after cranking the engine. There are two ways to retrieve any stored codes. One is to rent a code reader / scanner. That will display the code(s) by number or description. You can also cycle the ignition switch, then watch the flashes of the Check Engine light. Newer models display the numbers in the odometer display.
Turn the ignition switch from "off" to "run" to "off" to "run" to "off" to "run" three times within five seconds, then watch the Check Engine light or odometer. Don't crank the engine. If the starter engages even for a fraction of a second, that will abort the test sequence. Turn the switch off, wait about five seconds, then start over. The light will be on for a few seconds as a bulb check, then it will flash out a series of two-digit codes. After it goes off, in a few seconds it will flash on, typically once, then there will be a short pause, then two flashes and a longer pause before the next two-digit code starts.
Code 12 just means the ignition switch was turned off. Not all cars display it. If yours does, it can be disregarded. It's the next code(s) you're interested in. The last code will be code 55 which just means "end of message". If you think you miscounted, most cars will let you restart the sequence by turning the ignition switch off and back on one time right away.
If there are no codes stored in the computer's memory, you will have to check for spark and fuel pressure. Most of the time both will be missing although there will likely be a little fuel pressure which can be misleading. If only one of the two is missing, that system will need further testing. When both are missing, the best place to start is by determining if the automatic shutdown (ASD) relay is turning on. That relay will turn on for one second after turning on the ignition switch, and since it powers the fuel pump AND ignition coil / spark plugs, the pump will run for that one second. That's why it might appear to have fuel pressure. What is important is that relay must turn on again when you're cranking the engine. That will not happen if the camshaft position sensor or crankshaft position sensor are defective.
Caradiodoc
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Tuesday, September 14th, 2010 AT 3:50 AM
