I apologize for the book that follows ahead of time. Just trying to be as detailed as possible.

So I'm kinda at a point were I am scratching my head and I figured I might see if someone can chime in and give me some ideas. My 03 started the limp mode type surge about three weeks ago. (Pulls like a train up to a certain point depending on range and load and then falls on its face... rinse and repeat)

My first assumption was a dtc might be present so I checked and no codes found. I then proceeded to check fuel pressures and change filters (air and fuel). Fuel at idle to cp3 is 12 psi and at full load (as full as I can load it before it surges) it is dropping to 8psi. I know from my experience in rebuilding injection pumps that the cp3 doesn't have to have very much pressure as the gear pump can support it. This truck has the in tank dodge replacement.

I then moved to the high pressure side. I've got 6800 to 7000 at cold idle and pressure seems to come up nicely to 17250 or so before the surge kicks it back down to 12500 and the cycle repeats. When the fca is unplugged at idle the rail pressure immediately jumps to 26000. Fuel at this point seems to be being delivered at least to a point that I should be able to get the truck past 70 mph unloaded. I am now beginning to think my fca, rail sensor, map, or rail relief valve maybe to blame. I go ahead and swap all of those over with no change.

One of the symptoms that has come up also is very bad rail pop in 1st and 2nd gears when I rap them out. So I decide that maybe it's time to test these 250,000 mile injectors. I pop them out and head over to my local injection shop(premco) and we throw them on the tester. 5 out of six are shot and 4 of those five are pouring fuel to return. I start smiling thinking I've got this figured out. Wrong!!! Grabbed six new injectors and tubes and pop them in (I have installed these many times and fully understand the procedures for proper installation especially the tube torque). Truck continues with no improvement in rail surge but the pop is completely gone. Engine overall sounds much healthier and smoother. I think it was time for them anyway.

So now I start thinking about the apps maybe causing it to glitch so I measure all of the outputs and reference voltages. Everything tests out good and I attempt a throttle relearn validation with the battery disconnection trick. No change. From here I retire for a day or two and enjoy some cold beverages while I think about it. I get to wondering if my cp3 volume is bad so I decide to swap the overflow valve and gear pump. No luck. I rig up a gauge to test cp3 piston inlet pressure and I'm getting roughly 70 psi (I was using a gauge that goes to 300 because my other was already testing the fuel lift pressure). I then decide to pull the cp3 and have it tested. The pump checks out good! At this point I'm not sure if I should be happy or upset. Yeah I don't have to shell out $$$ for a pump but I'm nowhere closer to a solution.

OK so now it's sensor time. I go back over what I have done and swap the fca, map, rail pressure sensor again. I check all of the connections to them and the iat sensor by the air box. Plug in my obd data logger and check sensors and boost pressures ect. All seem normal. The rail surge has not let up one time since the very beginning(not intermittent) and I am inclined to believe that the ecm is shutting down the fuel system for a reason(some sensor completely out of range). Being that I am limited and do not have access to drbiii, I can only see the generic data (no cam sensor or crank readout). My last option I suppose is to beg for mercy at the *********** to have them lone me a tech and a scanner for an hour.

Any ideas fellas? Could a cam sensor cause this problem? I haven't changed it yet because it's kinda a pain to get to but if it is a possible failure point I may prefer that than dealing with the dodge house.

 

I would also like to note that monitored boost pressure is never the same when the defuel surge happens. Neither is the throttle position percentage. This causes me to think that it is probably not related to a sticking waste gate and over boost (although I know how that feels and it is similar) and it is probably not the apps due to inconsistency at throttle positions and the volage/percentage follows perfectly smooth with peddle pressure to wot.

 

any progress? very interested as I’m chasing something similar

 

Did you check the in tank pump for flow rate? Also check power and ground to the in tank pump. Low voltage or bad grounds will give you low pump flow. Pickup screen on intank pump could also be restricted. I use a headlight bulb to load test wiring at pump. Pump is grounded to frame rail and often corrosion at grounding point can lead to high resistance. Bulb should be as bright as direct connection to battery. Pin 4 and pin 1 power and ground, Remove and clean gound connection on frame. Check flow rate of pump min flow rate is 520 ml in 10 seconds. If below min drop tank and check pickup screen.

 

interesting. so i’ll add mine the rail pressure is 12000-16000 when it stumbles. has no problem pulling up to 22000-24000 psi. has no problem at full throttle continuing to pull will pull rpm wise all the way. but where it does occur is1/2-3/4 throttle intermittently and without consistency it will stumble briefly from 1800-2200 rpm cut out for a second. I’m throwing no codes and fuel pressure from lift pump is sufficient and not dropping below 10-12 psi at full throttle. ground wire isn’t corroded.

the problem becomes more prevalent when i run a smarty tune, but the blurps or cut outs do not show up on the reader as even a blimp in rail pressure. and the inconsistency or inability to recreate consistancly is making identifying it difficult.

with smarty programmer on and a 30 or 50 hp tune so very mild when it coughs its usually when engine is in first 10-15 minutes of firing up. its almost describable as a momentary bucking or cough but is giving no codes, no power loss per say because truck continues to pull but the action is violent enough feel truck surge and the surge isn’t just once sometimes it can be 3-7 surges in a short burst. when programmer is on, the cough i also get brief or occasional puffs of blacks mike that occur at the same time as the cough/surge. without the programmer on which is most the time i get no smoke but same surge.


I’m looking at ambient air temp sensor, map sensor maybe fica?

 

loose nut onto of injector number one, shorted out the fitting and melted the brass stud on top of the injector.

shop warranteed the work