Hi guys. You're overlooking one important comment. You said you only have 12 volts to the ignition coil pack for one second. That is exactly how the system is supposed to work. That 12 volts should come back, via the automatic shutdown, (ASD) relay, during engine rotation, (cranking or running). That is how the system stops the fuel pump from dumping raw fuel onto the ground if a line is ruptured in a crash. The engine can't run with no fuel pressure. No signals arrive from the crankshaft position sensor or camshaft position sensor when the engine has stalled. With no signal pulses, the Engine Computer turns the ASD relay off along with the fuel pump or its separate fuel pump relay.
If there was a fault code for the crank or cam sensor, they would have been erased if the battery was disconnected. They often will not set again from just cranking the engine. They typically set when a stalled engine is coasting to a stop. In that case, if you don't have spark, you need to look on the scanner under "Inputs and Outputs", or "Sensor Data" to see if the signals are showing up for those sensors. I have a Chrysler DRB3 for all of my vehicles. That one shows each sensor as "Present" or "No" during cranking. I'm not sure how that would show up on aftermarket scanners.
The scanner will also show when the ASD relay is being commanded on. You can do the same thing by measuring the voltage on the wire that is the same color at every injector, the coil pack, or either small terminal on the back of the alternator. That is usually the dark green / orange wire. Back-probe through the rubber weather-pack seal with a test light. Digital voltmeters don't respond fast enough. You will see the light turn on for one second when you turn on the ignition switch. That is when you'll hear the fuel pump run too. What is important is if the light turns on again during engine cranking.
Do you have a single or dual-cam engine?
Monday, March 20th, 2017 AT 5:01 PM