C-12 fuel issue

I have had some threads here and grasping at straws. I think I’ve narrowed it down to to a fuel issue. Today I replaced all lines from the tank selector valve to the engine driven pump on the motor with the exception of the one that goes from the engine driven pump to the fuel filter.

truck starts great and idles smooth. When you get it on the road unloaded and get after it it’ll pull hard and smoke for a few seconds then it runs out of that strong power and just makes do until the next gear change (eaton auto shift) when it idles down it acts like it’s allowing the fuel pressure to build back up and it pulls hard again and the cycle repeats. I have a new check valve for the filter base but don’t know if it’s needed. I found some metal in the fitting on the return line but it looks like it came from the fitting itself. I’m banging my head against the wall with this. Any ideas?

only thing I have touched is the fuel pump on the motor. Truck sat unused for 6 years and the previous fuel hoses were very hard and cracking. Assumed sucking air or return issue. Same issues persist

trying to get into freightliner for an evaluation but would like to fix it.

brett

 

Here’s the metal I pulled out of this fitting

brett