I guess I'll just describe the problem here, and we can move it to a new thread when I'm able to create one. I just needed to get all of this out for my own sake...
A few days ago, I went to start my truck and it cranked and cranked, but wouldn't even try to run. Seemed like a "no fuel" problem to me. I checked the fuel pump fuse and relay. I disconnected by new quick connect in the fuel line and turned the key to "ON" to see if it would squirt some fuel out at me. Nope. So I rightfully concluded the fuel pump wasn't pumping. Got it towed to my house.
I left my code reader at a friend's house 100 miles away last week, so I learned and did the "key dance" (thanks for the stickies!) to read my codes on my dash:
P0627 - Fuel Pump A Control Circuit /Open
P0522 - Engine Oil Pressure Sensor/Switch Low Voltage
Ok. I had read on this forum that the Oil Sensor switch is a common problem. It's $15 a the parts store, so I just replaced it. Still no start.
So, I wanted to just see if the fuel pump was getting power. Dropped the tank, voltage to fuel pump is 0.5v lower than battery. That's right at the threshold of a problem, from what I've read, but it is still over 12V with a fully charged battery.
Ran a jumper from the hot side of the fuel pump relay to the fuel pump, used on of the grounds from the fuel pump harness that plugs into the fuel pump. I opened the fuel qucik connect again and watched the gas dump out of it when I connected the jumper. So the fuel pump works. I reconnected my fuel line and connected the jumper again for a few seconds, to see if it would pressurize my fuel system enough to start. Then I plugged the harness back into the fuel pump and tried to crank it - and it started! Idled down. Ran and sounded completely normal for about 45 seconds, then promptly ran out of gas. So, the fuel pump works. (Which I knew was likely anyway...)
Now I figured I really need to look hard into the 7000 page service manual PDF I have. I searched P0627 and got a troubleshoot process for it. Step 1-3 were fine. Step 4 and I've already got an issue:
I plugged a 12v test light into the indicated (top) spot at the relay plug. No light with key turned to "ON". Note: I do get a light when I plug into the bottom of the 3 signal spots on the relay, but not in the top one that is indicated in Step 4.
Since I didn't get a 12v test light to come on in Step 4, the manual instruct me to
"Repair the open or short to ground in the (F942) Fused Ignition Switch Output circuit. Inspect the related fuse and repair as necessary"
It took my a some searching to conclude (perhaps incorrectly) that F942 goes through the #10 fuse in the interior (under dash) fuse box. The owners manual indicates that this "Ignition Run Only Out (R/O)". Fuse was good. I used by 12v test light in the supply to the fuse. It was off with the key off, and ON with the key on. Assuming I found the right fuse, there seems to be an open circuit between the the Ignition Run Only R/O fuse under the dash and the fuel pump relay. So, I'm at a wall on the P0627 / fuel pump issue. Unless it's being caused by the P0522 Oil sensor issue:
I've read in this forum that the Oil Pressure Sensor can cause a no start situation, presumably by cutting the fuel pump. So I recognize that this could be the ultimate problem here...
EDIT: I was using the troubleshooting guide for the 5.7. Everything below this is not valid for the 4.7, so I will have to start this troubleshooting guide over over.
I started the troubleshooting process for P0522. One step is to check the voltage on at the harness going into the oil presure sensor. It's supposed to be 5V, but mine i 12V! It's getting battery voltage. I would like to take the next step in troubleshooting which is:
Turn the ignition off.
Disconnect the C2 PCM harness connector.
CAUTION: Do not probe the PCM harness connectors. Probing the
PCM harness connectors will damage the PCM terminals resulting in poor terminal to pin connection. Install Miller Special Tool #881 to perform diagnostics. Measure the resistance of the (F855) 5-volt Supply circuit from the Engine Oil Pressure Sensor harness connector to the appropriate terminal of special tool #8815.
Is the resistance below 5.0 ohms?
However, I do not know which PCM harness is C2 (there are five harnesses going into the PCM and they look identical). I also don't have the special tool.
Any ideas on where to go from here?