Poor Fuel Mileage and Low Power

[Mopar1973Man]

11 minutes ago, BMC330 said:

Got around to replacing my VP44 today.  I have the same issues as before other than no hard starts when motor is hot.

 

Time to do an AC noise test of the alternator. What is your fuel pressure like at idle and at highway speed WOT?

 

12 minutes ago, BMC330 said:

The VP is from Pro Diesel.

 

I don't know the source of those VP44's and if they have been tested on a Bosch 815 test stand.

 

13 minutes ago, BMC330 said:

Any ideas where i should look next for my next to find the issues?

 

The biggest thing is test for AC noise and see if the alternator is creating issues for the ECM or possibly damaged the ECM from excessive AC noise. 

[BMC330]

The fuel pressure stays on 15psi.  I have a new fass fuel pump installed on the truck.

 

I have watched your videos and completed a AC noise test and it was within specs.

 

 

The will not start when engine is warm is back.

 

I am really lost.

[BMC330]

I hooked the truck up to a Matco Scan Tool this afternoon and drove it around 50 miles.

 

I had it on the live scan mode while driving.

 

The voltage to the ECM would go between 12 volts to 9.88 back and forth.  When the truck was at its lowest power point I was only showing 9.88 volts.  Could this be a ground issue?

 

The MAP was pretty much all over the chart also.  My boost gauge would show 10 psi and the scanner would go between 0 to 10 back and forth.  I also had 6 pounds of boost showing with the truck not running.

 

Im going to pull the alternator off in the morning and have it tested.

 

Are there any more things I can check in live scan mode that may help narrow my problems?

[Mopar1973Man]

17 minutes ago, BMC330 said:

The voltage to the ECM would go between 12 volts to 9.88 back and forth.  When the truck was at its lowest power point I was only showing 9.88 volts.  Could this be a ground issue?

 

Passenger battery terminal. All ECM, PCM and VP44 ground is right there.

 

Then if you want to get crazy and go for the ground mod.

 

19 minutes ago, BMC330 said:

The MAP was pretty much all over the chart also.  My boost gauge would show 10 psi and the scanner would go between 0 to 10 back and forth.  I also had 6 pounds of boost showing with the truck not running

 

Cummins ISB does some weird math to figure boost pressure. So I wouldn't consider this too bad might be part of it still.

 

 

[BMC330]

Ok,  pulled the alternator and had tested at the local Autozone.  Test was good.  Going to borrow Fluke multi meter to check AC noise again.  

 

If AC noise checks ok will move on to the ECM and VP grounds.

 

Thanks for all the advice.  Will advise if i find my issue.

 

One thing i noticed yesterday is throttal response is good until about a quarter of the way when accelarating. After that the truck pretty much will go flat until it reaches around 2000 rpm and the boost starts raising up.

 

Also i noticed the oil pressure guage moves to around 40 psi when the key is on.  Not sure if this matters just something I seen yesterday.

Edited April 7, 2018 by BMC330

[BMC330]

Alternator noise is .025 vac on fluke meter.

 

Going to OHM the throttle position sensor now.

 

[Mopar1973Man]

1 hour ago, BMC330 said:

Alternator noise is .025 vac on fluke meter.

 

Going to OHM the throttle position sensor now.

 

Better off watching the live data from the ECM. Ohm values don't mean much. You should see 0 to 100 prevent throttle signal. Rising smoothly. This can be done without driving.

[BMC330]

On the live data we found the TPS all over the chart.  Looked like watching a heart monitor when I put it on the graph mode.  Replaced the TPS and we are getting the same results.  

 

The TPS will read constant when only about 1/8 of the way depressing peddle.  The truck seems to run fine at that point.  If you mash the peddle any further the readings go all over the chart.

 

I am only getting one code and it is a PCM fault/3.

 

I have checked the grounds and found no issues.  I also unplugged the wiring going to the ECM to check for corrosion but it looked new.  

[Mopar1973Man]

What error codes are you getting?

[Dieselfuture]

I could be wrong but, it sounds like you might have something going on with your 5-volt Loop, oil pressure sensor is on that Loop if it's shorts out internally it will create these similar problems. Just my guess not saying you need to start changing sensors for no reason.

[BMC330]

No codes.  I am scanning again now.  I will advise asap

IMG_0561.3gp

[Mopar1973Man]

 

That should help. There is the rest of the wire maps in the articles.

[BMC330]

PCM abnormal is all i am getting.

[Mopar1973Man]

You might check the CCD bus for issues. The APPS sensor is shared by both ECM and PCM. If the CCD bus is goofy it might dirty all data. Remember the PCM is the primary computer the ECM is secondary.

[BMC330]

PCM abnormal is all i am getting.

 

Graph of apps sensor percent.  Wide open is 65%

[Mopar1973Man]

Just for crazy thought. Try unplugging the PCM then just key on and engine off run back through the APPS test again and see if the signal is correct. 

[BMC330]

We unplugged the first wire bundle closest to the drivers side and apps is smooth.  The graph looks perfect between apps percent and apps voltage.  And we are getting 100 percent on apps.

 

Not sure where to go from here.

 

 

Edited April 8, 2018 by BMC330

[Mopar1973Man]

I'm going to have to lean on the idea that you've got a damaged PCM. You saying you already getting a PCM abnormal error. Then where you unplugged the PCM the APPS signal returns to normal. Like I said I would have to lean on the idea PCM is malfunctioning. 

 

You might want to read this article too.

 

[BMC330]

PCM is what we are thinking also.  I have a friend who has a truck we may be able to borrow a PCM from to see if our symptoms go away.  If he will allow us we are also going to get the ECM.

 

I will advise when we have the PCM changed.

 

[Mopar1973Man]

Make sure its the same year and model and options.