Changed head gaskets and now want start

Fault codes never say to replace parts. They only indicate which circuit or system needs further diagnosis. While it's true a defective sensor is responsible for a code being set about half of the time, it's just as likely to find broken wires going to it, stretched terminals in a connector, or corroded splices. Sensors don't fail while doing other engine repairs. You're more likely to find a pinched wire, a plug left disconnected, or something along those lines.

Lets start with the actual code numbers you had. What were they and which parts did you replace?

When discussing an engine running or performance problem, you really need to include the engine size.

First, check for spark. When you find it missing, measure the voltage on the green / orange wire, (I think), to the coil pack or any injector. A digital voltmeter might not respond fast enough so a test light will work better. You should see voltage there for just one second after you turn on the ignition switch. That's the same one second you should hear the fuel pump hum. What's important is whether that voltage comes back during cranking.

If you see that voltage for the first second, the automatic shutdown (ASD) relay and circuit is working and the Engine Computer has control over it. If the voltage doesn't come back during engine rotation, (cranking or running), suspect the camshaft position sensor or the crankshaft position sensor. When the computer sees a signal from one, it knows it has to get the signal from the other one. When one is missing, it sets a diagnostic fault code for it. When both are missing, the computer won't know the engine is being cranked so it won't set any codes. That can happen when the camshaft position sensor is shorted. It kills the 5.0 volt or 8.0 volt power supply to both sensors. The computer shuts the supply down to protect it. You can find that by measuring the voltage to the cam sensor with the ignition switch in the "run" position. If none of the three wires has 5.0 or 8.0 volts, unplug the sensor, then cycle the ignition switch off and back on to reset the supply. If the voltage is on one of the two outer wires in the connector now, that sensor is shorted. If there's still no voltage, try unplugging the crank sensor. If that doesn't help, the supply wire is grounded someplace.

If you get a code for "cam and crank sync", double check the timing marks on the timing belt. Depending on which engine you have, if the belt is off one tooth, the Check Engine light will turn on and that code will be set. If it's off two teeth, the computer will shut the engine down to protect the valves. It does that by not turning on the ASD relay. At three teeth off, the open valves will hit the pistons and be bent.

That cam and crank sync code will also be set on the four-cylinder single overhead cam engine if the dowel pin between the camshaft and sprocket shears off. That lets the sprocket turn a little and causes late valve timing just like a jumped timing belt.

The first thing is to be certain the automatic shutdown relay is staying on. Measure the voltage at any coil or injector while cranking the engine. Use a test light. A voltmeter won't respond fast enough. I'm not sure of the wire color but it will be the same at all six coils and all six injectors. The test light must be on constantly during cranking. If it flickers off intermittently, the computer is getting an intermittent signal from one of the sensors. For that you will need a scanner that displays live data. It will show the cam and crank sensors listed as "no" or "present". If both are "present" and steady during cranking, something is wrong with the timing belt or there is insufficient fuel pressure.

If you're smelling raw fuel at the tail pipe, the ASD relay is turning on. I'm not sure what your last comment means. The engine will run on four cylinders if you hold the gas pedal down a little. If it won't, recheck the timing belt.

The cam is going to be 180 degrees off every other crankshaft revolution because it turns half as fast, but both cams have to be 180 degrees off or right on at the same time.

If it's in theft mode, the engine will typically run for one second each time you try to start it. You have to turn the ignition switch off between each attempt. Also, I seem to recall only the injectors are shut down. I could be wrong but if I'm right, the engine will run on starting fluid.

If it is indeed in theft mode and it won't reset with the door locks, suspect a disconnected switch in the doors or a broken wire between the door hinges. That would be quite the coincidence to have a problem with both doors but it is possible.

The next thing would be to find someone with a Chrysler DRB3 scanner to look at live data. It will list fuel as "Off" or "allowed". If it is allowed, it's not in anti-theft mode. There's a lot of decent aftermarket scanners out there but I don't know if any of them will display the Security system. The DRB3 also has a "no-start" menu.

Switching the ignition switch on and off three or more times within five seconds initiates the self test that displays fault codes in the odometer display, that's all. Once it's turned off again, or when you crank the engine, even for an instant, that exits the test mode.

As for what to do next, I'm lost without a scanner, otherwise there's no way to know what the Engine Computer is seeing and responding to. It will show whether fuel is being "allowed" or is turned off. It will display whether both sensors are developing their signals and whether they're in sync or not, and it will show if the automatic shutdown relay is being turned on.

Here's one last thing you might try. It was discovered by another person by accident while he was following something else I told him to look at. Find the automatic shutdown relay and bypass it with a stretched-out paper clip or piece of wire. Jump terminals 30 and 87, then try to start the engine. If it starts and runs, one of those two sensors isn't producing its signal.

On older cars the signals from both sensors were needed for the computer to turn on the ASD relay. On newer cars, and I suspect yours, both signals are needed during cranking for that relay to turn on so the computer will know which cylinder to fire first, but once it's running it can run if one sensor fails. Jumping the relay is bypassing the computer but the computer will take over once the engine is running.

If that works, suspect the camshaft position sensor first. As I recall, that's what the other person found to be the cause of the no-start. The signal from the crankshaft position sensor tells the computer which spark plug to fire next. That's critical. The camshaft position sensor's signal just tells the computer which injector to fire next. It won't matter if that's wrong. As a backup strategy on newer cars, the computer will just switch to firing the injectors at the same time as the spark plugs. The sprayed fuel will just sit there in the intake manifold and wait for the intake valve to open. That will kill the efficiency and performance, but it will run.