I'm running the Winter Diesel off the pump at the gas station, and also put in some Power Service (red bottle) de-gel.

I check the lift pump voltage by back probing the connector with the pump running and that was good. I can open the T-valve while running and have no issues. I opened the valve and turned the key on and it seems to have good flow. I even put a 10ft piece of clear line between the filter and the Inj pump and ran it out in front of the winshield and drove to work. Not seeing any air bubbles at all.

It seems that it may just be the Injection pump. I did get it replaced a couple years ago under the 120k warranty deal, and since it was replaced I have only put around 10k miles it.

What really has me hesitating on buying the New Inj Pump though is that 2 weeks ago I changed out the Crank position sensor, which was a struggle because I ended up with a DOA one from a local store but while I waited for RockAuto to send me the AC Delco one I ran it and my usual problems were gone while it was running in limp mode.

My thinking is that somehow the PCM is getting bad sensor input and is not commanding the Inj pump to run correctly because of the bad data it is getting. Now with no crank position sensor the PCM runs some basic code to operate (limp mode) and is not using the bad sensor data to command the pump.

Make any sense, or am I putting too much thought into it?

 

I took the truck in to a GM 6.5 mechanic. He reprogrammed the ECM with the latest calibrations as per service bulletin 77-65-26. That helped a little, but not a lot. The scan tool yielded code P1217, which lead to -- yes -- you guessed it -- REPLACE THE FUEL INJECTION PUMP. Pump was replaced. Truck runs like new.

 

There are several reasons that the code you got got could be thrown-last of which is to replace the IP.

A PMD can affect it as well as not adding enough lubricity additive to the fuel

Dealers tend to throw IP's at every 6.5 just because it pays more to replace than to diagnose properly.

 

Running a 1/2 to 1 ounce of 2stroke oil in our fuel adds life to these IP's probally 10 fold I buy Penzoil 2 stroke marine synthetic myself around $15 for a gallon around here