Hi to all and thanks in advance for taking your time to read this. Here it goes.......
I have been running around with this truck for 3 months now. Sat for winter. When went to put it into service in the spring truck ran for a few then died and would BARELY restart if at all. Started digging in and found bunch of crap in primary fuel filter. Pulled the sending unit and found about 3" of crap, rust & sludge at bottom of tank. Replaced tank & sending unit, cleaned out all lines, replaced fuel filters (w/Motorcraft) replaced fuel pump and cleaned entire block. Put all back together and truck fired right up & ran great. Gave back to customer. About a month later truck had not ***** and would barely move. Replaced the filters again (here was a little residual crap in them) and ran a cleaner through system & injectors. Truck great. 2 weeks later.... Yup! Same issue. Truck won't get out of its own way. Found posts about "blue spring" upgrade so did that F.O.C for customer (he's a great customer) and drive truck for 3 days. No issues. Very next day truck right back to what it was for him. Get it to shop. Can't duplicate it. Drive for a week- nothing. Customer takes truck back and within a week it's back here- no power except now it's dying and leaving his guys stuck on side of road for an hour. Can run in park or neutral and rev up. Once in gear won't rev whatsoever. Let it sit and Fire it up after an hour and it's mint. What am I missing!!? Everything checks out fine. FICM, IPC, injectors, fuel pump, fuel pressure, no issues with wiring or harness', no codes and all data is right on the money so WTH am I over looking!!? Any help is greatly appreciated. Thanks!!!!
Ps it's an 04 F350 6.0 4WD

 

Chris, Not sure what engine you are running or even if it makes a difference. I had THE EXACT symptoms two winters ago with my 6.0 Excursion and found air in the fuel line. Actually had to get two fuel pumps because the first replacement was still allowing air to get into system. Check for bubbles in fuel as it gets to engine. Hope this helps or gives you some direction.