2010 F150 5.4 70k miles. I was on the highway the other day and it started to stall. Slowly losing power over time. Pulled over and tried starting it. Idled low and rough. Finally died where it wouldn't start at all. No CEL on. Fast cranking, but no start. Had it towed to dealer. Next morning still wouldn't crank, but CEL light was on now. Diagnosed as bad FPDM. They replaced it and all was good. So I thought. About four days later I took it home and later that night I tried to start it, but it wouldn't. It would just crank, but no start. No misfire or anything. It had no intentions of starting! Tried like 6 times. Nothing. The next morning I was getting it towed again, when tow truck showed up I tried to start it. It started fine! Still had it towed. When it got to dealer service advisor said it wouldn't start. When the actual tech tried it worked fine! They drove it for nine miles, idled for two hours, etc. no CEL light and it's been ok since. This was like three days ago. I have a feeling it's not over. Any thoughts? I visually inspected FPDM, fuel pump, fuel pump relay and fuses. All good. I tried pulling the fuel pump relay while cranking and it behaved exactly as it did when it wouldn't start. Also, when I listen to the fuel pump, it primes for a couple of seconds, but it does sound weird. Kind of "crunchy."

 

not sure, but there may be a wire connector on frame below drivers side. if so, I would wiggle it with the truck running to see if it cuts off. Just an idea????

 

Good idea! Will do. I went under the truck today looking for that plug your referring to. I saw a YouTube video about it. I couldn't find it. Not sure if it applies to this truck.

 

I have no idea if this is related, but it's worth a shot. About a week before this happened I was driving with the AC on and the ac blower just stopped working. It wouldn't work on any speed. Tried shutting off truck to reset it and nothing. The next morning I went out to truck. Disconnected the blower connector and checked for voltage. It was perfect. Resistor was working across all speeds. Plugged connector in and everything worked perfectly. Hasn't been a problem since. I know the AC blower is on a different circuit so I don't think it's related, but it's worth a mention. Possibly a common power point for both circuits. Keep in mind I treat this truck like a gem. Maintained to the T!

 

Any problems starting today, goldeniz? Keep us in the loop; I'll be here to assist, if needed.

Crystal

 

So far so good. I just don't think after replacing the FPDM I should have one RANDOM problem. I feel it's just an intermittent problem. I ordered a wifi obd2 scanner that I'm planning on using with dash commander for iOS. My plan is to get a report of the problem when it's actually occurring. I'm interested to find out what my fuel rail pressure sensor reads when the problem occurs. That way I could take a "snapshot" of sensor data when the problem occurs.

 

Wow! Glad I mentioned the AC problem. After three weeks of the AC working fine today it stopped working again. Noticed the compressor wasn't turning on either. I disconnected the blower and tried again. Nothing. I went to the fuse/relay box in the hood. The second I opened it the AC started working. Wondering if I have a bad contact somewhere in there that's also affecting the fuel pump relay.

 

I was going to say fuel pump relay. I would look at that fuse box for a short somewhere, also, you might want to replace the relay as well. The fact that you are having two separate electrical issue makes me think that the fuse box/block is where the trouble lies.
There is nothing more frustrating than intermittent issues like that, where there is no real pattern or rhyme or reason. Good luck.