Crank but will not start until it has cooled down?

This is an extremely common problem on all brands. Most often caused by a failing crankshaft position sensor or camshaft position sensor. They commonly fail by becoming heat-sensitive, then they work again after cooling down for an hour. Most of the time they still keep working as long as you're driving. Natural air flow keeps those sensors cool. They like to fail when a hot engine is stopped for a short time, such as when stopping for gas, and engine heat migrates up to them.

One of the frustrating things is very often there will not be a diagnostic fault code to direct you to the circuit that needs further diagnosis. The Engine Computer needs some time to detect the missing signal, but the engine typically stops rotating too soon. Codes for those sensors often don't set just from cranking the engine.

The easiest way to figure out which circuit to look at is with a scanner to view live data. Under the "Inputs / Outputs" menu or "Engine Data" menu, both sensors are listed. I have a Chrysler DRB3 scanner for all of my vehicles. They list each sensor with a "No" or "Present" to denote whether the signals are showing up. Both will be listed as "No" with the ignition switch on, then both should switch to "Present" as soon as you start cranking the engine. When the stalling has just occurred, you're looking for the sensor that does not switch to "Present" when you crank the engine. There are quite a few nice aftermarket scanners today that display the same data. If you don't have access to one, you'll need to have a mechanic perform the test, but it has to be done while the problem is occurring.

It's important to understand, regardless if you're working from a diagnostic fault code or from the missing signal on a scanner, neither one ever says to replace a part or that one is defective. When a sensor or other part is referenced in a fault code, it is only 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 before spending our customer's money on that part.

In this case, since this has been such a common problem, you might consider just replacing the crankshaft position sensor since it costs less than a trip to the repair shop. On older engines there was a very simple but important procedure to set the depth of the sensor. Yours is fixed with its mounting ear, so you just push the sensor in and bolt it snug. You can reach it from on top. It's near the driver's side of the engine, above the transmission.

The instructions say to raise the vehicle, which implies replacing the sensor from underneath, but I don't recall having to do that. If you do, please be sure to use jack stands:

https://www.2carpros.com/articles/jack-up-and-lift-your-car-safely

Let me know what you find, and if you need the instructions for replacing the camshaft position sensor.

What has been replaced, one of the sensors I mentioned? The crankshaft position sensor for 2003 is of a newer design in which you simply push it into place and bolt it down. The location of the mounting ear sets the air gap, so it is not adjustable.

The camshaft position sensor is of the older design where you have to set the very critical air gap. That is done with the use of a thick paper spacer. The photo below shows the sensor with its slotted mounting hole, and an expanded view of the spacer in the upper left corner. New sensors will have that spacer already installed. Those are expected to get scraped off as soon as the engine is cranked, so you don't want to remove that sensor multiple times. If you expect to remove it and reinstall an old sensor, that spacer can be cut in half to allow for two installations.

The spacers are available separately for around $3.00, but that used to be for a pack of ten. I don't see that reference now in the parts listing. A number of aftermarket replacement sensors have a thin plastic rib molded onto the end of the sensor to set that air gap. Here again, you push them in as far as possible, then tighten the bolt. That rib will wear away as the engine runs.

In my ten years at the dealership, I did replace about a dozen transmissions when the specialist got backed up. That job required removing the crankshaft position sensor to avoid damaging it. At first, to save a few cents, I cut those spacers in half, but eventually I became too arrogant and stopped using them. I just pushed the sensor all the way in, then pulled it back 1/16" inch, (by feel). A few worked out okay, but the last one came in two weeks later for intermittent stalling and a diagnosis of a failing sensor. While that could have been a possibility, it's more likely I had the air gap set wrong. This is why I add the comment about "mechanical issues" with a part referenced in a diagnostic fault code. Those codes only tell you the circuit that needs further diagnosis or the unacceptable operating condition. They never say to replace a part.

We never want to suggest throwing random parts at a problem in hopes one will solve it. Normally that is the most expensive and least effective way to do it. One of the few exceptions to this are these position sensors. Because they do have such a high failure rate in the manor you described, replacing one is the less expensive first step in the diagnosis process. Once that most common solution doesn't pan out, we can move on to the more involved steps. I'm happy to hear you have a scanner. Watching for which signal drops out is something most people have to leave to their mechanic. Hopefully this will tell us which circuit we need to look at. Let me know what you find.

I have a friend who won the national Independent Trucker of the Year award some years ago. But I've only been in a large truck once, back in the early '70s. I think they're cool. Also helped another friend replace the back half of the frame on a dump truck last year and straighten the box after it was tipped on its side. Much fun.

Now I know you understand what I was saying about replacing random parts. I'll be waiting to hear how this turns out with the new sensor. Please keep me updated.