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+---- Thread: dd15 can not get primer hard (/Thread-dd15-can-not-get-primer-hard)
dd15 can not get primer hard - Rjpierma24 - 12-24-2025
Have a truck towed in, 2014 dd15 two filter fuel system. Motor is set back so its a pain to get to fuel pump. But truck will start with starting fluid and run fine, as soon as you shut it off wont start. Go right to hand primer and its soft, i pump it and never stays hard. Small and big filter both have fuel in container, i pulled return line and as soon as i prime it fuel starts leaking out. Any suggestions where to go from here? No matter what i do it wont get hard on the hand primer.
RE: dd15 can not get primer hard - MaxEcu - 12-24-2025
Question is how much pressure do you get in the rail when cranking? does it have any codes? did you even scan with diag tool?
RE: dd15 can not get primer hard - Rjpierma24 - 12-24-2025
Rail pressure shows like 300 bar cranking, goes way up when it’s running. No codes. At all. I put a pressure gauge on low side. Can only prime to about 25 psi and then it slowly drops. Running it’s at 75 psi
RE: dd15 can not get primer hard - Semi_Workin - 12-25-2025
sounds to me like your low pressure pump is out. it’s integrated with the high pressure fuel pump i believe. at least that’s always been my solution whenever starting fluid starts it right up or if you prime it with a pump.
RE: dd15 can not get primer hard - RYAN8543 - 01-12-2026
(12-24-2025, 06:03 PM)Rjpierma24 Wrote: change the primmer 1st
Change the primmer then change fuel filters when changing the fuel filters look down inside the filters housing, the large filter canister, many times people the filters in wrong and it will break the lower part prevent fuel flow.
U can see this by looking down inside it, this engine fuel system has3 or 5 check valves in the housing or on that side or pump.
This engine normally has the above wrong but if not check the quality control valve itself but it normally doest leak. NOTE a failing primer is a bad primer flat out. So start with that first