Ok, I know this has been covered before but I can't find the old post so here we go again. It appears that the fuel in the filter is low after the truck sits for a week or two. Very low RPM's for a few minutes... then it's OK. Non turbo NH 230, with new filter. Pokey

Probably a Pinhole in the fuel line somewhere

Fuel could be draining back. A check valve before filter would work if that is the problem. Joe D.

Pokey,
I am by know means an expert but more of a loose cannon mechanically. I changed fuel line etc. and my problem was gack getting over the intake in the tank? took tank off and cleaned it and problem solved!

Brian

Cummins engines are prone to fuel drain back if the engine has some hours on it. Possible sources of air intrusion are: at the tachometer cable drive on top of the pump, and at the fuel filter head, if the filter is mounted directly on the back end of the pump. A third source possible is at the fuel line to pump fitting if your engine has a remote mounted fuel filter.
To test the tach cable connection, disconnect the tach cable at the pump and remove it. Start the engine and let it idle. Take a small amount of diesel fuel in a cup and pour the fuel over the connection where the tach cable hooks to the pump. The center of the shaft will be turning. Now observe the puddle of fuel. If the fuel disappears by being sucked into the pump, the tach drive seal is bad. This will allow air into the fuel system when the engine is running, and allow fuel to drain back when the engine is shut down.
If your fuel filter is mounted directly onto the rear end of the fuel pump, air leaks can occur between the filter head and the back of the pump. Because this area is under suction when the engine runs, no external fuel dripping is seen, but when the engine is off, air can leak in, allowing fuel to drain back. Using the correct size Allen wrench, tighten all the Allen head screws that mount the filter head and pulsation dampener (small rectangular piece next to filter head) to the rear of the fuel pump.
If you have a remote mounted fuel filter, (hose between pump and filter head) Remove the fuel suction hose from the back of the Cummins fuel pump. Now loosen the jam nut and remove the fitting that the suction hose was connected to. Note that the "suction fitting" has an "o ring " under the jam nut. Replace this "o ring." It is also a potential source of air leakage.
These three areas are where Cummins pumps are most prone to problems. As other members have posted, replace the suction line between the pump and tank, and inspect the connections for the fuel line to tank. Good luck.

Thank you Jeff, Joe D., Brian, and Stan. It looks like I have some homework to start on. Pokey

Sorry Ted!!! Thanks! Pokey

Sunday afternoon I pulled the tach drive cable off the top of the fuel pump and poured in a little fuel while the truck was at an idle and the fuel just sat there, no leaky O ring. Next I took the fuel line off between the fuel pump and the filter and found the O ring hard and flat, so that was changed. Started the truck and let it run a bit. It has sat scince Sunday so I gave it a try tonight after work and it fired right up with good RPM's. Thanks Stan pretty easy fix when you have the right coach! Pokey

Glad things worked well for you Pokey. Sometimes I manage to learn things after doing them for 35 years!