I installed a FASS pump yesterday, because I believed my lift pump crapping out. It seemed to repair all the problems I was having, except for running very rough when starting. I'll go to start it up of the morning(45-50 degrees) and it runs rough for the first 1-2 minutes. After this time passes it runs good. I should also mention when I start it up throughout the day, when it's up to temperature, it starts up fine. What could this be, and also is it safe to drive. Thank you in advance.

 

How about filling out your signature so we know about your truck.

 

Sorry, I forgot about that. I've got an 03 5.9, 3500 4x4 with a 6 speed manual. I just purchased it about 2 months ago. It has 72,500 miles on it. It's completely stock, except for a straight pipe. This is the only problem I've only encountered since i got the truck.

 

This sounds similar to what I had when my fuel heater started to seep around the rubber seal. It [I]could be[I]that you have a minor air leak into your system. After running, it takes awhile for the air to get into the system. When it sets for a while, the leak will let just enough air in to make it start rough. Leave it be for a day or so (if you can) and I bet it will fire then stall. If so you have a seep in the fuel line somewhere. Being as how you just messed with the fuel system, I would start there...Good luck

 

Is there any chance that it could be the grid heater? I'm not 100% sure how this works but it runs fine after 1-1.5 minutes of running. If the grid heater heats the air going into the engine, which I think it does, this could make sense to me why it won't run when it's cold. I should also mention their is a little white-gray smoke that comes out of the pipe when trying to start it the first time in the morning.

 

Unless you are somewhere cold, I doubt it's the heater. When I had a seep in my fuel system, I would have to crack injectors almost every morning. When I did this the truck blew out white smoke until I tightened the injectors up. I assume (and someone will correct me) the the white smoke is from poorly atomized fuel. I'll bet you have a small,small leak somewhere and you are slightly losing your prime..

 

While I'm not a 3rd gen guy it still sounds like you may have a grid heater out or a relay to them is gone. The grid heaters are in operation in various combinations starting when ambient air is 50 f or lower. Without the grid heat it will run pretty rough untill a little heat is developed in the cylinders.

Wait untill it is -20 f . You will learn a new definition of running rough and blowing smoke. haha

 

Actaully I've started my 03 at -25 and it made minimal smoke. This sounds like maybe an injector giving out or a RP relief valve. These 3rd gens bleed air very easily especially with a good lift pump like a FASS. Mine didn't even smoke after I swapped the head and the whole fuel system was dry. My .02

 

The dealer said it was probably the grid heater and he said most of the time it will be covered by cummins warrnty

 

I doubt its air in fuel, I had to completeley remove my entire system on my '06 and put it back on. Once it was on bump the key a couple times truck fired and ran rough once it bled the air off truck ran great and no problems since that was 70K miles ago so start with grid heater. Just my .02

 

I drove it today and the problem of the sputtering out (feels like lack of fuel) is now happening when I let of the clutch in 2nd and when i step on in 3rd and fourth. I installed the FASS pump to fix this, which it did, FOR A 5 DAYS. I am thinking their has to be some relation with it starting bad when cold and the fact that it sputters out when warm.