A friend has a 2004 (8-03) D3500 6 speed manual service truck with 156K that starts and runs good cold, but will lose power and stall when it reaches operating temp.
A five star dealer thought they had fixed it but it lost power and shut off on the interstate 3 miles from their shop.
A very good local diesel mechanic then kept it several weeks driving it with scanner and gauges attached. He even swapped the pump to his test pump which he said pumped a little less pressure. At no time did he get a code or find the rail lost pressure when it lost power and stalled with either pump.
I put on my scanner which I bought for my gas vehicles. It only reads a few inputs. TPS seems to operate smoothly. Intake temp reads correctly. Coolant reads right with the truck temp gauge and the truck warms to a steady 196-198. Vehicle speed and rpm reads right with the truck gauges too.
The truck seems to have good power and smooth engine until it reaches operating temp. Then it almost always loses power. It will not accelerate then in 5th at 2200 rpm and 55mph and if you upshift to 6th it will "chug" at 1500rpm. Downshifting back to 5th will make the engine run smooth again, but it will still not accelerate on flat road.
MAP reads 29.5 switch on, about 32 idling, around upper 30's cruising, and maxes at about 65. % load seems to correspond to actual load cruising, but I caught it go from near 0% to 56% load as it idled no load at 750rpm to a stall yesterday with clutch disengaged.
Truck seems to want to idle at around 950 instead of 750 sometimes when it is acting up, but that doesn't keep it from stalling. When it is running good it will not stall starting off at idle in 1st or 2nd gear.
Sometimes it will run all day without a hitch after it gets past the initial warm up disaster. Sometimes it will act up after cooling down slightly.
During cranking it will sometimes "kick back" against the starter. Most times it will turn smoothly start or no start.
I hope this makes sense and someone has a solution! Thanks.

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Finally got a code out of the truck this AM. P0251 for what that is worth.

 

How old are the batteries, and are they charging normally? I'm not where I can look it up right now, but IIRC, p0251 is low ECM input voltage, usually caused by bad batteries.

VP44 truck? P0251 = Inj pump cam sys

Probably time time for a new VP.

 

date posted above is 8-03 that would make it a 04 which is a CR.

 

It'll a problem with the CP3 then - either way it's gonna be injection pump-related.

 

either that or he's got a problem and his computer is tryin to get into limp mode. that would explain the power loss

 

Batteries were changed when problem started with no change. As I stated in first post , local mechanic swapped pumps with no change in performance. He also changed the FCA.

 

I want to remember someone having a similar issue and it was the connection at the ECM...have you pulled that connection and verified there is no corrosion?

 

we have an 03 with the same problem it starts just fine but then when it gets up to opp temp it dies and wont start we put an air dog on it and new FCA but still no luck

 

Thanks I will check the connection.

 

what was wrong with ours was our back three quil tubes were not torqued to 41 ft-lbs so once we did that and torqued our lines to 22 ft-lbs we fired it up and she ran normal again so to check yours pull off your FCA and shake it it should rattle put it back on aafter that then pull off your return line off the back of your head and put it in to a cup you can measure with a graduated cylinder or paint cup if it fills up to more than 70 ml in ten seconds there is your problem we had 250 ml in ten seconds also our rail high pressure release valve wasnt out but bad its supposed to release at 30,000 psi ours would leak with the shop air house and had a lil leak we put one off an isl cummins and it ran a lil stronger than stock so over all we put
AIR DOG transfer pump
new FCA valve
NEW high pressure relife valve
and she was back to running order no stalling or loss of power