Hello here is a break down of the faults,

The fix is most likley plugged differentral tubes for the egr system. Or bad egr valve both common Other causes

Malfunctioning EGR differential pressure tubes
A damaged EGR valve
A stuck open turbocharger control valve
A low reading from the EGR differential pressure sensor
A low reading for the EGR valve position sensor
High exhaust temperatures
Low coolant level
High coolant temperature
An incorrect coolant/water mixture
A stuck closed variable geometry turbocharger
A fouled EGR cooler.

ok, I am here

what would cause severe ‘backfire’ 1500 rpm & lower? this symptom quit when check engine lite came on steady.

did you get my last post?

yes. is the backfire related to the egr system?

You still there?

Backfire would be related because there is too much fuel and not enough air

okay, do i have the active code 27 right – differential pressure high?

the egr valve recycles exhaust gasses to be reburnt and the engine expects this and witll black smoke and carry on

27 is not a fault the other 2 that you provided are egr related and would cause your symptoms

well, when the check engine lite came on steady today, it quit back firing and quit smoking at lower rpm’s. seemed to gain the little bit of power i had been lacking since the back firing.

The only way to check is get cummins software or bring to dealer and have them test the componets via computer controled checks.

okay, the 27 code may come from a reader not specifically designed for the cummins isx.

how is your air filter ? i have seen engines back fire from plugged filters> Yes 27 could be OEM related i could cross the other 2 you provided to cummins faults as i provided the details above

my problem is my shop manager hates cummins, and does not understand what differential pressure even means (ie he wanted me to explain to him where the differential is on the engine.

ok not a problem

The exhaust gas recirculation (EGR) differential pressure sensor has two ports that sense exhaust pressure. The sensor outputs a voltage which represents the pressure difference between the two ports located across an orifice in the EGR tube. The electronic control module (ECM) uses this pressure to determine how much exhaust gas is flowing in the EGR connection tube to the intake manifold. This information is used to control the EGR valve for correct emission levels.

The ECM provides a 5 volt supply to the EGR differential pressure sensor on the sensor supply circuit. The ECM also provides a ground on the sensor return circuit. The EGR differential pressure sensor provides a signal to the ECM on the EGR differential pressure sensor signal circuit. This sensor signal voltage changes based on the differential pressure in the EGR crossover tube.

The EGR differential pressure sensor measures the exhaust gas pressure drop across the EGR differential pressure orifice. This pressure drop is used to calculate the amount of EGR flow into the intake manifold.

Component Location

The sensor is located near the air intake.

low intake flow to engine = black smoke over fueling

air filters are checked and or replaced every 10k miles (we work in some pretty dusty places sometimes)

ok than you will have to follow the direction the faults leas

sorry faulkts\\

sorry faults lead

Do you have cummins insite at your shop?

yep, that’s what i figured. I only drive the truck, and the shop manager (of the shade tree variety) thinks all truck drivers are dumb. No, no certified techs on site. they look at the codes, order parts and wait to see what happens.

oh that kinda troubleshooting can get costly. Now a days you NEED the software to properly troubleshoot. You can’t swing the bat and guess. too complicated and expensive

I happen to have a BS in engineering (electronics – PC hardware) wasn’t making enough money w/o a PHd, went back to trucking. will have to pass this info on to the President of the company and most likely send to Cummins. Our problem as most small companies is treading water with this economy. and I most likely will NOT be able to expense this with the Company. will be able to write off with the IRS, at least for this year…

oh ok

it’s worth the investment it WILL pay for it’s self with in a few months fix it right the first time!

I understand the need for ALL the correct tools. Heck, the Shop Manager doesn’t even use e-mail. He absolutely HATES that I have a laptop and a wireless modem that I use exclusively for mapping and having stuff faxed to me.

old school hu. well this day in age everything is changing so fast it’s impossible to do anything with out electronics

and he HATES cummins…. like I said, I will talk with him first and if I don’t think he is cooperating i will take to the guy who pays for it. How bad does this affect the MPG’s? I’m only getting about 4.6 running about 67 tops

had it up to about 5 just before the smoking and backfiring started getting real bad over the past three weeks.

extremely bad the engine will only run peak when ALL is working as programed in the ecm calibration.. This is something you might want to look into also. The ecm needs updates time to time to correct fuel econ, and other glitches in the system. with the software you could keep all units up to date with current cummins revisions and updates for the ecm. With the wngine in this condition as i said you are over fueling (useing MORE fuel than needed to perform)

makes perfect sense to me. I thought this engine when running properly should get closer to 6 mpg when running 63-65. with the price of fuel….

5-6 is pretty normal (hard to believe)

Okay, so do I hit the accept button now? Doing so will pay you the measly pittance of $18?

lol yes if your happy. thank you

please feel free to request me in the future. I’m always here to help.

Yes, I am now a happier camper. You pretty much have backed up what I was already leading to. Thanks XXXX XX MUCH for your info and patience.

Anytime thanks again