2008 Dodge 6.7 Cummins running terrible. Injector driver?

Cummins injector driver testing

2008 6.7 came in no start, customer replaced injectors still same thing.

Fuel rail pressure was erratic, tore back down and redid injector job 3 fuel supply tubes were loose.

Crank it no start, checked cam and crank signals are pcm compared to known good

The only thing I have found is it's running off of low voltage around 25v to the injectors, I believe these are supposed to be 50v piezo injectors. This reminds me of a power stroke 6.0 running with a bad FICM I captured two injector pulses, one when the engine is running smooth and the other when it is plooming white unburnt fuel smoke and barely running

Health report on all modules led to a CAN B - circuit code. Traced that down and repaired pin at TIPM

Now trucks running

It will idle but very rough with little white smoke of unburned fuel - burns your eyes-

Any throttle it completely falls on its face and clouds of white smoke

Unplugged FCA runs at full fuel same condition

Verified 10 psi of fuel pressure from lift pump

Exhaust is open turbo is not stuck in full closed position

Intake is clear

All pcm powers and grounds have been load tested good

All injector circuits from pcm through valve cover harness load tested good

Scoped injector circuits and noticed they are all firing with 22 volts +- a little. Aren't these 50+ v piezo injectors? That low voltage had me concerned as the ground path for the injectors is directly following the voltage curve, I scope a identical known good truck and saw a perfect waveform like id expect.

So I am asking, I'm 99% sure I have weak injector drivers in my computer as I have load test and pin fit checked all my pcm grounds. Anything I may have missed

I do know the 6.7 liter has IQA (Injector Quantity Adjustment) coded Bosch injectors that need to be programmed. Each fuel injector has a six-digit alphanumeric correction code. The correction code is printed on the intake side of the fuel injector and is used to identify injector calibration. When replacing any fuel injectors, this code must be entered into the vehicles Powertrain Control Module (PCM) using a diagnostic scan tool. If they are not programmed they won’t leave a code but they sometime they will perform erratic. Also any remanufactured non-Bosch injectors you have installed that is not rebuilt thru a certified Bosch process, you have to wonder if they are performing according to Bosch’s standards. I know it’s considerable savings for purchasing remanufactured injectors, but a lot of issues can happen from non-Bosch remanufactured injectors if not thru a certified Bosch process.
Along with verifying the common rail pressures. I read you verified lift pump pressure. You will also need to verify lift pump volume. If that is good, compare in your scan tool “Actual” pressure vs. “Desired” fuel rail pressure, they should be very close. If that is good, you need to verify return fuel volume from injectors, in case of a worn or not seating balls and seats from the injectors. If pressure is not the same, they sell caps to isolate injectors to see if rail pressure comes up, if it does you have found the bad injector. Also you mentioned that you have white smoke, it may be an injector or the cylinder has a low compression that would possibly give the same result of a bad injector. Any chance you get, if you remove any injector again, get a compression test in the injector hole with an adaptor, and verify its cylinder compression. Hope this helps.

Nope no codes, I've ran the truck several times for a couple minutes to see if it would set something but it never did

I edited the first message above, p[lease read.

IQA codes have been entered into the pcm, supposedly the truck ran this way prior to the injectors being replaced.

Lift pump pressure was in spec

Volume test came back with 530 ml in 10 seconds.

Injector return test was 45 ml in 30 seconds with rail pressure commanded to maximum under fuel pressure leakage test. All 6 injectors were isolated one at a time and measurement was between 42-48ml across all 6.

Fuel rail pressure desired and actual pressures are within a couple hundred psi, it is hard to go off that as poorly as the truck runs.

I was trying to post this question a couple weeks ago but had issues with a new forum update and could not since then I have learned the following

The customer had a charging system voltage code. He diagnosed that as a faulty pcm. Send the computer out to be "rebuilt" and reinstalled. Still had the charging issue, and the truck ran like crap. He said he had needed injectors for sure before he replaced them for a issue with them returning to much fuel and causing a low rail pressure issue underload. So he replaced them thinking that was why it ran like crap after the PCM was "rebuilt" . When that didn't fix It sat for months and was towed to me. I found the charging code to be a dirty battery terminal.

Did you look at the injector voltage waveforms I posted in the original post? The ground path for the injectors has 25+v on it back proved at the UVC.

Me being confused by that I had a friend stop by with an identical configuration truck and scoped his as well and got the second sample waveform.

I'm at the conclusion that there is something faulty with the new computer. This truck isn't a rush as he doesn't have the money to dump into it for a wrong diagnosis ( also a friend's truck) so I'm trying to do as much research as I can on it before calling a $3500 replacement computer from the dealer

The fuel injector should be 50 volts. I would say you do have a power supply issue to the injectors.

What year was that from, my second picture I captured looks proper to me that I took from a known good truck. Do you have a waveform of the ground path

That was a 2008 6.7 liter. And no the pic was from another forum I found. I had to remove it due to the watermark on pic from other forum. Are you able to post the current waveform?

This is the current waveform

My current clamp was broken when I was looking at the truck a couple weeks ago, I didn't get a current sample.

Do you have any thoughts as to the low voltage I'm seeing? Barking up the wrong tree?

I'm very familiar with the engines and maintain a fleet of 63 of them (UPS) . The typical checks have all passed on this truck

ginuwine11 wrote:

The fuel injector should be 50 volts. I would say you do have a power supply issue to the injectors.

To this, as far as how I am reading my injector pulse captures my ground has 25v on it, like the ground path is the issue

So is the supplied injector power feed reading 25v if the injector is unplugged at the harness connector? Also unplugged, anyway you can backprobe injector power feed at PCM for any of the injectors for the voltage reading?

I did not test with the harness unplugged,

All injector circuit wires were load tested back to pcm

I have been unable to determine which power feed is for the injectors specifically, but all power feeds and grounds were also monitored backprobed while engine was running and no anomalies were found, good grounds solid power feeds

As far as 25V on the ground side, If this is ground side switched, and you don't have the 25V being pulled to ground, then yea I agree PCM is not doing it's thing.

They are ground side switches with 50v constant

I wonder if the 6.7 has any strategies in place for the ECM. Not sure that ECM may have shut down the injector driver control side due to a low voltage supply to injectors, not sure. I think I have exhausted all information, it looks as though you have load tested powers and grounds to ECM and all is good.
You can also look up on a scan tool for the PID's, BALRCYL1 – BALRCYL6 Balancing Fuel Flow Rate. They are for each cylinder. It will display a positive or negative number. A "0" ( Is the ideal perfect number) means the ECM is not adding or subtracting any fuel to get the optimum crankshaft rotational velocity (torque). If you see a negative number such as "-1.5", the ECM has decided that cylinder is being over fueled and is now taking fuel away and opposite for a positive number. This will give you some information on how well the injectors are doing and working.

Final update, I sourced a used PCM and reflashed the VIN with EFI Live , truck starts and runs perfect no other issues.

Was a bad injector driver internal to the pcm

Good deal, and thanks for posting a followup!