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04 Dodge Stratus won't start again

My 2004 Dodge Stratus with 2.7l V6 has been good to me, now up over 140K miles. Lately, though (twice), I drove it a under a mile, shut it off, and when I returned to it could not get it to start. It turned over just fine, but didn’t seem to be firing. When I returned several hours later, it started, running roughly for awhile. Once it smoothed out, it ran just fine, and I’ve had no other problems. My mechanic had a similar problem with a Dodge pickup of the same year, and it turned out to be the crankshaft sensor. Is there anything else we should be suspecting?

Next time it doesn’t start, hook a spark detector* in line with a spark plug to see if there’s indeed spark.
If it indeed has spark, spray some starting fluid into the air intake.
If it now coughs like it wants to start, it likely is fuel related in that it doesn’t get enough.

If it still doesn’t start, it could be a leaky injector that floods the engine when left for a little while. When left for longer, the leaked gas has evaporated and then it will start fine.
You can try running some techron through a gas tank to see if it gets better.

*http://www.harborfreight.com/inline-ignition-spark-checker-69014.html

Just to clarify, this has only happened after a short drive, never during cold start. Today, I noticed that within the first few minutes of driving it bucked a bit, almost imperceptibly. After that first few minutes, it smoothed out just fine.
If there is no spark, and (as yet) it hasn’t set a fault code, do you have any suspicions based on this engine? And is there any way to determine which injector might be leaky? Does the Techron help because the valve inside the injector is sticking?

Yes, techron is a pretty decent cleaner so it may take care of the leaking injector. It is a cheap thing to try.

I’d try the other things first to eliminate the ignition as being a problem and wouldn’t immediately assume the injectors are bad. You could pop them out and see how they behave but let’s save that for later, after you know it isn’t the ignition. For instance, high fuel pressure could also cause injectors to leak. There are places that will clean and refurbish them, if replacement is cost prohibitive.

Another possibility is a defective coolant temp sensor. The fuel injection system adjusts the fuel/air ratio based on the coolant temp. It should be injecting less fuel when the engine is warm. If it continues to think the engine is cold, that could result in hard warm starting.

Likewise, anything else affecting the fuel/air ratio could cause this. Leaking or clogged injectors (as mentioned above) or an air leak, a vacuum hose or device leaking. If you car has a “cold start injector”, that could the problem too. I doubt your car has one though.

Fuel injectors are pretty reliable and usually are not the cause of this problem. And they are difficult to test properly. Verify the cause isn’t somelthing else before considering the fuel injectors as the cause.

Good point, George. I had a car that did that.
Often cars have a limp mode, where they override the condition and start if you’ve tried to start it X number of times. They’ll run really rich but it will run.

More clues! My wife and daughter have discovered how to get the thing to start when it does this, which makes me suspect George’s coolant temp sensor and flooding. If we crank, then floor it, she’ll fire up. There is no short period of running rough when we do this.