Even faster, start with reading and recording the diagnostic fault codes. Chrysler made doing that yourself much easier than any other manufacturer, but they stupidly dropped that on late model vehicles. If it still works on 2008 models, cycle the ignition switch from "off" to "run" three times within five seconds without cranking the engine, leave it in "run", then watch the code numbers appear in the odometer display.
If you have spark and fuel, there's no need to waste your time checking the fuel pump and the other things you listed. You know multiple ignition coils and spark plugs wont all fail at the same time.
Be aware too that Mackinblue@gmail. Com's suggestion to check the valve timing is a good one, but it most likely does not apply here for a couple of reasons. First of all, this engine uses timing chains instead of a belt. Those are not likely to break or jump. Second, there is a safeguard built in to prevent valve damage. I am not sure if this is an interference engine, and I am not sure if this applies to this engine, but on other Chrysler engines the engine computer will turn on the check engine light and set a diagnostic fault code if the timing belt jumps one tooth. It will shut the engine down and prevent it from restarting if the belt jumps two teeth. If it were to get to three teeth off, valves would be hit and bent by the pistons. The fault code would be "Cam and crank sync".
It is important to understand the computer turns the automatic shutdown, (ASD) rely on for one second when you turn on the ignition switch, then again during engine rotation, (cranking or running). The ASD relay sends current to the ignition coil packs, injectors, alternator field, oxygen sensor heaters, and the fuel pump or pump relay. The fact you have steady spark proves the ASD relay is being turned on.
If you have sporadic spark during cranking, the ASD relay may be not staying on steady. That would point to what tells the engine computer the engine is rotating. That is the crankshaft position sensor and the camshaft position sensor. Fuel pressure can be misleading because even with a failed sensor, the ASD relay still turns on for one second when you turn on the ignition switch. If you can hear it, that is when you will hear the fuel pump run, and that one second is enough time to get the fuel pressure up to normal. Since the injectors likely are not firing, fuel pressure won't be bleeding down.
In the past a signal was needed from both the crank and cam sensors for the computer to turn on the ASD relay. That changed on some models starting in the early 2000's. You might get the ASD relay turned on, and you might have spark, but not injector pulses. If that is the case, try a little starting fluid. Chrysler's are the only cars that you can run the engine with the fresh air tube removed from the throttle body. Most engines from all other manufacturers require all incoming air to go through their mass air flow sensor to be measured so the right amount of fuel can be calculated. Chrysler never used a mass air flow sensor on their domestic engines.
If you do not have any relevant diagnostic fault codes, you will need a scanner to view live data while cranking the engine. The cam and crank sensors will be listed with something like "No" or "Present". Often fault codes for those sensors do not have enough time to set simply from cranking the engine. They usually only set while a stalled engine is coasting to a stop.
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Sunday, November 27th, 2016 AT 5:44 PM
