Well, let me back up ............
Trying to diagnose a random crank no start — has happened twice over the last week.
While cranking, I get plenty of ICP pressure, ficm is good — but I noticed on my edge insight that RPMs were at “0”. Even though i was getting a crank and it didn't sound like a starter issue, my buddy went underneath and tapped on the solenoid. After a few taps, I cranked and the RPM’s went up and the truck started. Not sure how this would be related but wondering if there is a bad sensor that is telling the engine there are no RPMs to start? I definitely hear the engine itself cranking over and have plenty of oil pressure
The reason I wasn't more confident in that assessment is highlighted above.
You want to be confident of the repair, and confidence may be hard to deliver. That said - I am
sure that the most common cause of a loss in rpm signal is a CKP or CKP wiring issue.
You posted some conflicting information and you really are posting no numbers/data (except a "0" rpm that isn't consistent):
1. Plenty of ICP pressure and a weak crank don't necessarily go hand in hand
2. It didn't sound like a starter issue, but you "imply" that tapping on it caused the rpm's to be stronger and you actually got an rpm signal then?
3. You did get it to start after tapping on the starter
So please verify a couple of things.
1. When you said the "rpm's went up", did you actually mean you then
got an rpm signal or was it simply an audible increase in rpms?
2. When you get the no-start, are you losing Cam/Crank Sync or FICM sync?
3. When you get the no-start, are you getting a fuel pulse width signal?
4. Might as well post up the actual ICP cranking pressure and volts, and the IPR %duty cycle. I would prefer to see this information when it doesn't start, but just getting data at any point would help.
5. Might as well post actual voltage numbers for the FICM (MPower, LPower, AND
VPower) when cranking!
In summary - your issue is an intermittent one so it is going to be hard enough to identify, let alone over the internet. If you were able to start it, then the contributing issue had temporarily gone away. How do you test in confidence for an issue that may not be there when you are testing?
You didn't post any codes. We need a check for codes with a good code reader. Maybe an electrical code for the crank sensor will show up.
Also, I am not the biggest fan of the Edge insight, so I am not familiar with it. I don't know if it
was having issues reporting an rpm value or the PCM wasn't getting one. Were you getting a dash gauge rpm indication?
You can check the resistance between the CKP connector on the PCM Pin 30 (harness side) and Pin 41 (harness side). Resistance should be 300-400 ohms. Just be aware that checking it on an intermittent short or open circuit may or may not reveal anything. Also, check the connector and the harness wiring for chafing. CKP wiring near A/C compressor and belt tensioner is a common chafe point.
If tapping on the starter improved the crank, then it sounds like a starter issue also. That said, a starter issue won't cause a "0" rpm reading when you know it is actually cranking.
These may help (but I haven't looked them over in quite awhile):
CKP removal and installation: