Hello
I just purchased a 07 GMC Sierra 2500 147K that has been sitting for weeks. It wouldn't start for the transport guy but I got it to start after the 3rd attempt. Each time I would crank a short while (didn't want to overheat the starter) and the 3rd time it caught. After that it started fine but codes for the cyl 3 and 5 glow plug came on and code P0087 for fuel rail low pressure. I cleared them and drove for about 15 minutes and only P0087 came back on. It seemed to drive fine around town and when I accelerated hard to get on highway the exhaust blew some black smoke. I am new to duramaxes and see they have many sources of leaks and some say a need for a lift pump.

I took it to a well-known diesel shop and the tech plugged up his laptop and showed me the fuel rail pressure wouldn't go about 9K whether he revved it or commanded higher pressure from his laptop. The CEL light was not on since I cleared it that morning before the drive. He said it needs new CP3 and scheduled a day for replacement (2K). On the drive home the CEL light came on and although it felt fine on the highway it was sluggish around the town driving and fuel rail pressure would not go above 11K. I cleared the code and it drove okay but I parked it (didn’t' check rail pressure though).

A day before repair day I wanted to make sure it started and ran it with the scanner plugged in and could get pressure up to 15K and went driving and saw pressure as high as 21K. I emailed the tech and he said that it isn't the pump and to keep driving it and monitor the values. He didn't want to change the filter because it looked new but I think I will now first.

The fuel filter head/primer assembly looks newer, the bleed screw looks new and the tech crawled underneath and said it looks like the previous owner tried looking for solutions because the shield around the tank looks like it has been tampered with

 

If you are driving the truck and at WOT you are seeing 21k Rail pressure is the actual what is the desired? Does this truck have a Race valve in the back of the fuel rail? Typically this is the first thing i would look into.

 

I'll have to check into the race valve but got a lot of response elsewhere telling me to change the filter first. It appears newer but just to eliminate the cheapest possibilities first.