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Hello group,
I'm at my wits end on trying to figure out what's wrong with my dakota thought id try here and see if someone might help. So I rebuilt my 4.7 a few months ago myself. All new parts top to bottom, coil packs plugs gaskets chains you name it was new. Was running like a top until it died suddenly. After cranking it once I heard a rattling coming from the front of the engine. I assumed it was a chain. So I trailered it home and tore it down to find a chain guide on the passenger side broke cause it to have slack in the chain. So I bought a new chain kit from napa.insatlled it made double sure my timing marks lined up and tdc. Put it back together and no start. I replaced the crank and cam sensor thought that would be the problem with no avail. I am getting spark i checked with a extra plug and I am getting fuel checked the fuel rail and had plenty of pressure. It acts like it wants to start but pops out the intake and won't throttle up. Almost seems like its starving for fuel. There is a check engine light one which I ran the code by turning the key on and off 3xs came with a po1391 code. Also no rpm signel when cranking. I also replaced the pcm with a new one and still no change. Anyhelp would be greatly appreciated. Im stumped at this point on what it could be. Thanks for the help
 

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I suspect you have already found that P1391 means intermittent loss of CMP or CKP signal. That would be verified by the no rpm signal on the tach when cranking. I'd inspect all the wiring for both sensors, checking for continuity between the sensor and the PCM. Good work on doing the rebuild, including the timing chain set. I've not done that on a 4.7 and it looks like a real PITA.
 

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Discussion Starter #3
Yes sir I've traced them back as far as I could with nothing found. I checked the cam sensor with a test light with ignition on and it had power. They are all new Mopar sensors as well... thanks it was a task to say the least to rebuild it. Oh and it has brand new heads as well. Anything else I can check to be the culprit?
 

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From the FSM:

"ENGINE START-UP MODE

This is an Open Loop mode. The following actions occur when the starter motor is engaged.
The PCM receives inputs from:

† Battery voltage
† Engine coolant temperature sensor
† Crankshaft position sensor
† Intake manifold air temperature sensor
† Manifold absolute pressure (MAP) sensor
† Throttle position sensor (TPS)
† Starter motor relay
† Camshaft position sensor signal

The PCM monitors the crankshaft position sensor. If the PCM does not receive a crankshaft position
sensor signal within 3 seconds of cranking the engine, it will shut down the fuel injection system.

The fuel pump is activated by the PCM through the fuel pump relay.

Voltage is applied to the fuel injectors with the ASD relay via the PCM. The PCM will then control
the injection sequence and injector pulse width by turning the ground circuit to each individual injector
on and off.

The PCM determines the proper ignition timing according to input received from the crankshaft position
sensor."

You said you were getting a P1391 code. If the PCM is not getting a crankshaft position sensor signal, it will shut off fuel thru the injectors with the ASD (automatic shutdown) relay. Saying that the CKP sensor is new does not mean that a signal is getting to the PCM. Get a wiring diagram, determine which wire delivers that signal TO the PCM and check that a signal is being generated. You can also "rent" a noid light set and see if the injectors are getting a pulse signal, especially more than three seconds after you begin cranking the engine.
 

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Hey, Old Marine,
I know that the crank & cam shaft pos signals are essential for a start, but are all the other inputs listed also essential for a start?

From the FSM:

"ENGINE START-UP MODE

This is an Open Loop mode. The following actions occur when the starter motor is engaged.
The PCM receives inputs from:

† Battery voltage
† Engine coolant temperature sensor
† Crankshaft position sensor
† Intake manifold air temperature sensor
† Manifold absolute pressure (MAP) sensor
† Throttle position sensor (TPS)
† Starter motor relay
† Camshaft position sensor signal

The PCM monitors the crankshaft position sensor. If the PCM does not receive a crankshaft position
sensor signal within 3 seconds of cranking the engine, it will shut down the fuel injection system.

The fuel pump is activated by the PCM through the fuel pump relay.

Voltage is applied to the fuel injectors with the ASD relay via the PCM. The PCM will then control
the injection sequence and injector pulse width by turning the ground circuit to each individual injector
on and off.

The PCM determines the proper ignition timing according to input received from the crankshaft position
sensor."

You said you were getting a P1391 code. If the PCM is not getting a crankshaft position sensor signal, it will shut off fuel thru the injectors with the ASD (automatic shutdown) relay. Saying that the CKP sensor is new does not mean that a signal is getting to the PCM. Get a wiring diagram, determine which wire delivers that signal TO the PCM and check that a signal is being generated. You can also "rent" a noid light set and see if the injectors are getting a pulse signal, especially more than three seconds after you begin cranking the engine.
 

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I don't think all the other inputs are necessary for a start. The PCM uses inputs from all those sources to ensure that the engine will run properly during and after the start (coolant temperature, air temperature, air pressure, throttle position, etc.) As stated, the PCM DOES need the crankshaft position signal to keep power to the injectors and coils, through the ASD. If the PCM disables the ASD, you will not receive power to the coils or fuel injectors.
 

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Thanks, Old Marine.
Am I correct that the PCM MUST get a signal from the can position sensor for a successful start?
 

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Did you make sure new sensors were synced? Just a thought. I had a no start issue that boiled down to that

Hello group,
I'm at my wits end on trying to figure out what's wrong with my dakota thought id try here and see if someone might help. So I rebuilt my 4.7 a few months ago myself. All new parts top to bottom, coil packs plugs gaskets chains you name it was new. Was running like a top until it died suddenly. After cranking it once I heard a rattling coming from the front of the engine. I assumed it was a chain. So I trailered it home and tore it down to find a chain guide on the passenger side broke cause it to have slack in the chain. So I bought a new chain kit from napa.insatlled it made double sure my timing marks lined up and tdc. Put it back together and no start. I replaced the crank and cam sensor thought that would be the problem with no avail. I am getting spark i checked with a extra plug and I am getting fuel checked the fuel rail and had plenty of pressure. It acts like it wants to start but pops out the intake and won't throttle up. Almost seems like its starving for fuel. There is a check engine light one which I ran the code by turning the key on and off 3xs came with a po1391 code. Also no rpm signel when cranking. I also replaced the pcm with a new one and still no change. Anyhelp would be greatly appreciated. Im stumped at this point on what it could be. Thanks for the help
 

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From the FSM (with regards to the 4.7L engine):

The CMP sensor contains a hall effect device called a sync signal generator to generate a fuel sync signal. This sync signal generator detects notches located on a tonewheel. The tonewheel is located at the front of the camshaft for the right cylinder head. As the tonewheel rotates, the notches pass through the sync signal generator. The pattern of the notches (viewed counter-clockwise from front of engine) is: 1 notch, 2 notches, 3 notches, 3 notches, 2 notches 1 notch, 3 notches and 1 notch. The signal from the CMP sensor is used in conjunction with the crankshaft position sensor to differentiate between fuel injection and spark events. It is also used to synchronize the fuel injectors with their respective cylinders.

The FSM doesn't specifically state that a CMP signal is required for start, but based on this, I would presume that it is.
 

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Thanks Old marine.
I always appreciate your informative answers.

From the FSM (with regards to the 4.7L engine):

The CMP sensor contains a hall effect device called a sync signal generator to generate a fuel sync signal. This sync signal generator detects notches located on a tonewheel. The tonewheel is located at the front of the camshaft for the right cylinder head. As the tonewheel rotates, the notches pass through the sync signal generator. The pattern of the notches (viewed counter-clockwise from front of engine) is: 1 notch, 2 notches, 3 notches, 3 notches, 2 notches 1 notch, 3 notches and 1 notch. The signal from the CMP sensor is used in conjunction with the crankshaft position sensor to differentiate between fuel injection and spark events. It is also used to synchronize the fuel injectors with their respective cylinders.

The FSM doesn't specifically state that a CMP signal is required for start, but based on this, I would presume that it is.
 
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