About a week ago, my 6.7 started having trouble turning over. I disconnected the fuel lines from the secondary fuel filter in the engine bay, disconnected the ground on both batteries, and then reconnected everything. This let me get the truck started, but it only runs fine once it’s going. From what I’ve read, the lift pump has a mechanical part that keeps pressure high enough for it to keep running after startup. The issue is only when cranking. Yesterday I tried to start it again, but nothing happened, even after doing the same troubleshooting as before.
Here’s what I’ve tried:
Tested fuse voltage and got 11.5 Volts at the engine bay fuse box, so the relay should be good.
The leads on the wiring harness connected to the fuse box look fine, not burnt like some videos I’ve seen.
Made sure there’s no gas in the diesel tank to rule that out.
Replaced both fuel filters.
Tried cycling the ignition on/off several times before attempting to crank.
Tried testing the voltage at the pigtail going into the fuel pump, but the color coding on the wiring doesn’t match the harness under the fuse box. I got 6V on one lead when grounding to the frame.
What is your fuel pressure reading? Are you sure it’s a fuel issue? If it is, which side is it—low or high? Any codes showing up? These new trucks could have a bunch of different problems that can cause a no-start.
@Luca
When I had the codes up, I got PCM U0109 and P064A, plus a couple of others. I can share more once I get another read—my batteries are charging now after I ran the acc mode for too long.
Zeke said: @Luca
When I had the codes up, I got PCM U0109 and P064A, plus a couple of others. I can share more once I get another read—my batteries are charging now after I ran the acc mode for too long.
It sounds like the computer is trying to talk to the fuel pump control module but can’t. The U0109 and P064A codes both point to issues with communication with the fuel pump control module and fuel pump module performance. That’s definitely a big reason why it’s not starting. To know if that’s the main issue or just one part of it, you’ll want to check out the other codes. You’ll need service data to know how to fix it, and a scan tool that can decode modules and talk to the FPCM will be super helpful. The first thing they’ll want to know is whether the FPCM is working or if it’s totally dead.
Zeke said: @Luca
When I had the codes up, I got PCM U0109 and P064A, plus a couple of others. I can share more once I get another read—my batteries are charging now after I ran the acc mode for too long.
I had the same codes on a 2019 F550. The fuel pump driver module was losing power due to some electrical fretting in a connector behind the driver’s wheel well. You should check the power at the FPDM, usually found on the cross member near the fuel tank or on the frame rail.
Zeke said: @Luca
When I had the codes up, I got PCM U0109 and P064A, plus a couple of others. I can share more once I get another read—my batteries are charging now after I ran the acc mode for too long.
P064A points to a problem with the fuel pump. If you see shavings in the fuel pump screen, it’s time for a new fuel system.
I’ve run into this issue a few times recently. It’s probably the fuel pump relay, which is internal to the battery junction box. This part isn’t serviceable and it’s been a common problem. Starting in 2020, they made the BJB serviceable without replacing the entire harness.
If I remember correctly, the 6.7s have the same fuel pump control module on the frame, just like the F150s. If that goes out, you’ll lose the lift pump, and if you’re getting a code that says you lost communication with it, that’s probably the issue.