4.7 rebuild. Crank no start.
#21
If you have a meter that can measure duty cycle or percentage, measure that across the coils. You MIGHT get a usable reading.
A "factory" dwell time is around 20-25 milliseconds (0.020-0.025) to charge before the ground is released. A full 720 degrees of crankshaft duration is about 0.300 of a second at 400 cranking RPM. So "at best", you'll see about 8% duty cycle of 12 volts - 1 volt RMS. This is why a noid light is almost required to be able to see the sequence, a consumer meter just isn't fast enough.
If the coils were firing in any way, even if way out of firing order, you'd hear it missing or firing out the intake/exhaust or trying to catch. If it's just spinning over doing nothing, I'm questioning that ignition system.
I haven't touched a 4.7 but based on my hemi, I'd find it hard if not impossible to plug the coils in the wrong order. Being a 2002 yours should also be the single spark plug, I don't think the 16-plug 4.7's started until 2004/05?
A "factory" dwell time is around 20-25 milliseconds (0.020-0.025) to charge before the ground is released. A full 720 degrees of crankshaft duration is about 0.300 of a second at 400 cranking RPM. So "at best", you'll see about 8% duty cycle of 12 volts - 1 volt RMS. This is why a noid light is almost required to be able to see the sequence, a consumer meter just isn't fast enough.
If the coils were firing in any way, even if way out of firing order, you'd hear it missing or firing out the intake/exhaust or trying to catch. If it's just spinning over doing nothing, I'm questioning that ignition system.
I haven't touched a 4.7 but based on my hemi, I'd find it hard if not impossible to plug the coils in the wrong order. Being a 2002 yours should also be the single spark plug, I don't think the 16-plug 4.7's started until 2004/05?
Last edited by magnethead; 11-09-2023 at 10:56 PM.
#22
I do see counts increasing when cranking. I do not see an option on this scanner to fire coils. I removed the fuel pump relay when testing and then reinstalled to see if I could get a reading on INJ (ms). I assume that is the injector firing time in milliseconds? I do not get a reading. It did however fire more than it has. I drained old gas and put fresh in. Sounds like it is only firing on four cylinders. Should I try better plugs?
#23
#24
Took the PCM out to try and see if something could be wrong with it and pulled the plug on the back and it is full of an oil like substance. That cannot be good. Read where this could be the conformal coating that has melted or fluid that has wicked from the wire harness into the plugs and then the PCM. Going to attempt to open PCM and see if it is damaged.
#27
#28
I have read where the power steering pump pressure switch gets a leak and forces power steering fluid up into the wire buddle and by capillary action makes its way to the PCM. It looks like motor oil, but does not smell like it. It does have power steering fluid smell to it. This would explain why I had oil in most of my connectors. Learn something new everyday.
#29