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05 wont start

2K views 9 replies 4 participants last post by  pershingd 
#1 ·
I need help I can't get my 4.7 to start. Drove to store and came out and it wouldn't start. Reset the computer and started, ran for 3 days then did it again, replaced to computer and nothin. I've replaced cam crank and map sensors along with fuel pump and still nothing. Any ideas?
 
#4 ·
I assume it turns over? Does it try to fire when turning over? What happens when you actuate the accerator pedal while turning over? Do you have a scanner that you can look at some parameters?

IGNITION SWITCH (KEY-ON) MODE
This is an Open Loop mode. When the fuel system is activated by the ignition switch, the following actions occur:
1. The PCM pre-positions the idle air control (IAC) motor.
2. The PCM determines atmospheric air pressure from the MAP sensor input to determine basic fuel strategy.
3. The PCM monitors the engine coolant temperature sensor input. The PCM modifies fuel strategy based on this input.
4. Intake manifold air temperature sensor input is monitored.
5. Throttle position sensor (TPS) is monitored.
6. The auto shutdown (ASD) relay is energized by the PCM for approximately three seconds.
7. The fuel pump is energized through the fuel pump relay by the PCM. The fuel pump will operate for approximately three seconds unless the engine is operating or the starter motor is engaged.
8. The O2S sensor heater element is energized via the ASD relay. The O2S sensor input is not used by the PCM to calibrate air-fuel ratio during this mode of operation.

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:
1. Battery voltage
2. Engine coolant temperature sensor
3. Crankshaft position sensor
4. Intake manifold air temperature sensor
5. Manifold absolute pressure (MAP) sensor
6. Throttle position sensor (TPS)
7. Starter motor relay
8. 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.

ENGINE WARM-UP MODE
This is an Open Loop mode. During engine warm-up, the PCM receives inputs from:
1. Battery voltage
2. Crankshaft position sensor
3. Engine coolant temperature sensor
4. Intake manifold air temperature sensor
5. Manifold absolute pressure (MAP) sensor
6. Throttle position sensor (TPS)
7. Camshaft position sensor signal
8. Park/neutral switch (gear indicator signal—auto. trans. only)
9. Air conditioning select signal (if equipped)
10. Air conditioning request signal (if equipped)
Based on these inputs the following occurs: 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 adjusts engine idle speed through the idle air control (IAC) motor and adjusts ignition timing. The PCM operates the A/C compressor clutch through the clutch relay. This is done if A/C has been selected by the vehicle operator and requested by the A/C thermostat. When engine has reached operating temperature, the PCM will begin monitoring O2S sensor input. The system will then leave the warm-up mode and go into closed loop operation.

IDLE MODE
When the engine is at operating temperature, this is a Closed Loop mode. At idle speed, the PCM receives inputs from:
1. Air conditioning select signal (if equipped)
2. Air conditioning request signal (if equipped)
3. Battery voltage
4. Crankshaft position sensor
5. Engine coolant temperature sensor
6. Intake manifold air temperature sensor
7. Manifold absolute pressure (MAP) sensor
8. Throttle position sensor (TPS)
9. Camshaft position sensor signal
10. Battery voltage
11. Park/neutral switch (gear indicator signal—auto. trans. only)
12. Oxygen sensors
Based on these inputs, the following occurs: Voltage is applied to the fuel injectors with the ASD relay via the PCM. The PCM will then control injection
sequence and injector pulse width by turning the ground circuit to each individual injector on and off. The PCM monitors the O2S sensor input and adjusts air-fuel ratio by varying injector pulse width. It also adjusts engine idle speed through the idle air control (IAC) motor. The PCM adjusts ignition timing by increasing and decreasing spark advance. The PCM operates the A/C compressor clutch through the clutch relay. This happens if A/C has been
selected by the vehicle operator and requested by the A/C thermostat.

CRUISE MODE
When the engine is at operating temperature, this is a Closed Loop mode. At cruising speed, the PCM receives inputs from:
1. Air conditioning select signal (if equipped)
2. Air conditioning request signal (if equipped)
3. Battery voltage
4. Engine coolant temperature sensor
5. Crankshaft position sensor
6. Intake manifold air temperature sensor
7. Manifold absolute pressure (MAP) sensor
8. Throttle position sensor (TPS)
9. Camshaft position sensor signal
10. Park/neutral switch (gear indicator signal—auto. trans. only)
11. Oxygen (O2S) sensors
Based on these inputs, the following occurs: Voltage is applied to the fuel injectors with the ASD relay via the PCM. The PCM will then adjust the injector pulse width by turning the ground circuit to each individual injector on and off. The PCM monitors the O2S sensor input and adjusts air-fuel ratio. It also adjusts engine idle speed through the idle air control (IAC) motor. The PCM adjusts ignition timing by turning the ground path to the coil on and off. The PCM operates the A/C compressor clutch through the clutch relay. This happens if A/C has been selected by the vehicle operator and requested by the A/C thermostat.

All of the above information came from the factory service manual. I am currently chasing down a gremlin on my 2004 Durango with 5.7. Good luck and let us know what else you find.
 
#6 ·
Please don't take this the wrong way (sometimes things written get taken the wrong way because you can't see any expression, etc.) , but I have to ask: Do you have and know how to use a meter? If so, you need to back track it to the Fuel Pump relay. Remember that your fuel pump relay will get deenergized after 1-3 seconds of the vehicle not running unless you are cranking the motor or the motor is running. So, with someone cranking the motor, start at the connector and work your way back to the Fuel Pump relay. If you go to crank the vehicle, it just cranks? Do you have a scanner that you can connect up while cranking and monitor the "Commanded Throttle Position" and "Actual/Relative Throttle Position"? What happens if you crank vehicle and apply partial throttle at the same time? Will start or attempt to start? The PCM knows the motor is cranking from the Crank Position sensor. I have a similar situation going on with my 5.7 Hemi, where it cranks, tries to start and then gives "Commanded Throttle Position" of 0.3% and wont start until I give it a little throttle. Keep us informed and feel free to ask questions.
 
#8 ·
You are welcome for the help. Sounds like you have a broken wire or a bad connection. Now the really hard part; finding where you are losing the voltage to your fuel pump. You say you have it at the relay and not at the harness connector; time to start chasing that particular harness. Sometimes it helps to have a partner when you are cable dogging wires, harnesses, or looms. One person gently tugs while the other person feels and looks. Any place you have a sharp bend or turn, look closely. Where are you checking for the voltage from the relay? If you have a test light and poke through the insulation of the applicable wire on your harness, try the half way point of the harness. If you have it there, split the distance in half again, (working your way from the relay toward the harness connector behind the wheel) keep doing this until you lose it, then you will have narrowed down the section of the harness that you are losing the fuel pump voltage. Likewise, if you didn't have it at the halfway point, then work your way back toward the relay until you have it using the same method. The three things I would do right off the bat, is check my test light ground connection by connecting my test light to ground and then checking a known power source to verify my ground connection is good and my test light actually works, the use the test light right at the beginning of the harness (as close to the relay as possible) to verify that it is actually coming from the relay socket and applicable connections, and then back probe the harness connectors behind the wheel to see if it is my connector or not. Then I would start cable dogging my harness. If you have to cable dog the harness, remember to check bends and turns. Fortunately for me, if I had to do this, I have a lot of electrical/electronics experience and special tools for this type of task. Hope this helps. Keep us up to date. Thanks, Calvin.
 
#10 ·
I had much the same thing happen to me. I gave up and towed it to the dealer who diagnosed it as a failed integrated power module (the black box with relays in it). Basically there's a fault in the wiring to or from the fuel pump relay causing your problem. They replaced the box and all has been fine since.
 
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