I have my buddies 2001 2500 4X4 to help him fix. He is currently deployed in a sandy land far away.
Thanks in advance. I love this site!

Now I know you have heard this part before but let me give you the timeline

My buddy Bought truck
Truck wont start on hill nose up below 1/4 tank
Truck wont start hot below 1/4 tank occasionally
He Took to wizbang diesel shop They installed new VP44 and a bully dog
Problem still there
Other issues (Cutting out on freeway)made my buddy change to an edge programmer. Solved that issue
I Installed new frame mount air dog and siphon tube kit in tank and edge unit per some advice he received.
Factory in tank pump removed.
I Installed new isspro gauges
Installed new Bypass valve cummins P/N 3941156 after reading about it here.
Now when you turn the key the fuel pressure reads 15 PSI very quickly.
Truck still cranks for 20 to 30 seconds on a hill
Truck starts in 2-4 seconds on flat. this is with 1/4 tank of fuel
When under full throttle on setting two, fuel pressure is not lower than 12PSI and the boost will go to 30PSI. A side note. I get a weird whistle starting at about 18 to 20 PSI of boost.
Tonight when I get home I am going to park it tail up and see if that changes anything on the start in the morning.
I hope this is enough info to get some advice. I am almost out of hair to pull.

 

Sounds like you have a bad vp44 or are getting air in the fuel line.

Any codes? Key on/off 3 times, watch odometer screen.

 

try filling the fuel tank, diesels seem to start better when they have fuel.........

 

JohnH You funny guy cowboy!

Tank is 1/4 full. My 03 Runs on Less than that and so does my 2000 and my other buddies 2001

Today I placed the truck on a 30* Hill for 6.5 hours
Went to start, Fuel pressure went up for a few seconds then down to 0 Pump was running. Truck would not start
Rolled down to flat ground. Fuel Pressure came back up and truck fired after cranking for 20 seconds.
The only reason I do not suspect the tank is because the problem was there for both the stock fuel pick up and the new siphon tube.

Thanks again for the help

 

maybe your sender is off and your really less then 1/4 and fuel is exposing pick up tube end on a hill

 

I'd take the fuel line off at the VP in them situations, un-plug the Air Dog relay first. get something to catch the fuel.

if memory serve me correct, jump the orange and red wire at the relay and the Air Dog will run with the key off or on, leave key off.

see what it is pumping and how fast. it should fill a gallon jug in 10-15 seconds.

to stop the pump, un-plug your jumper, that way you can control the pump not the ecm.

a 6" jumper wire with 2 male spades work good. the relay is the one supplied with the Air Dog wiring harness, not the fuel pump relay in the truck.

 

i still think 1/4 tank of fuel is too close to empty, try filling it and see if the same starting issues are there

 

That doesn't necessarily mean anything......each truck can differ, and there has been non-stock parts added.
I would tend to agree with JohnH and Rebal.......
The fuel sending units on these trucks are not known to be very reliable....the one in question may not be reading accurately. As John said, add say 10 gallons to the tank and test again.

 

how far is the siphon tube from the bottom of the tank?

30* do you live on a mountain?

if it is running good when parked and shut off primed, I'd think that it should still start "then" die of you were not getting fuel from the tank due to the hill/incline

 

The senders in these trucks go bad over time. I can't count how many times we have told people with supposedly 1/4 full tanks to put 5 gallons in and it fires right up.

If it gets to 1/4 tank, see how many gallons it takes to completely fill the tank, that will tell you if the sender is beginning to read wrong.

 

I backed the truck up the hill this time. Let sit for 6.5 hours. Truck started right up with the same amount of fuel.
Aftermarket tube is was put in top of tank when air dog was installed.
What is bugging me is that the problem was their when my buddy first bought the truck before any changes were done.
I am not giving up.
Gauge could be off. I will put 5 gallons more diesel in it today and try again.
More news later
Thanks for all the help! My buddy will appreciate it when he gets home from Afghanistan.