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This is my first 6.7 injector job and this is a little different animal than any other diesel I've worked on. I replaced the injectors, and coded them with my scan tool, in this pickup and now have low rail pressure. The only code I have is P2291 Injector Control Pressure Too Low - Engine cranking. Low pressure side is functioning properly but the high pressure side is not building pressure at all. The only components I had to remove were the charge air cooler tube to the turbo, fuel filter, ccv filter assembly, injector supply and return lines, and the injectors. I did have to unplug the pressure regulator at the back of the fuel rail on the left side. I don't think I ever hit that with a wrench or anything but I'm thinking that it might be dumping rail flow to return. I am working on rigging it up so I can check that without making a bigger mess than I already have. I don't know if it's possible to have an air lock somewhere, but I've never had that on any other hpcr diesel I've worked on. I am going to try to get a test on this pressure regulator now. I have a little data to post as well. If anyone has any ideas, please throw them out because this guy needs his pickup urgently. Thanks.
I have determined that the cp4 high pressure pump is not pushing fuel. I only have lift pump pressure and flow to the rails. The regulator duty cycle is about 40% with and amp draw of 1.2 while cranking. I back probed the connector to the regulator and have 3.5 v. I replaced the regulator valve with no change. I am ordering a cp4 in the morning.
Check your oil level did it go up? Those fuel rail injector tubes are one time use same with the fuel rail pressure sensor. make sure they're not leaking before firing a $1400 part at it if you have not already.
I appreciate the input. Oil level was just a tad high but no indication of diesel and it hasn't gone up any with all of the cranking. If I was dumping enough fuel into the cylinders to not have rail pressure I would think I should have hydro lock issues or at least significant fuel in the oil. With the lines from the cp4 loose at the rail I get lift pump flow with key on. I don't see any increase at cranking.
I talked to a couple of pump shops and they think there was enough wear in the area of the pump plungers that the ingress of air while replacing the injectors created a situation where the pump will not build pressure anymore. There was no metal, or anything at all, on the regulator screen. They say that happens with a bottom end failure of the pump and not normal wear of the pumping components. This pickup has about 150,000 miles on it but it is deleted and tuned with the tuner set to max hp all the time. It's a kid's truck. He also doesn't use any additive.
The boys at the pump shop were right. I have to admit I was skeptical, but I put the cp4 in and it runs. Apparently the old pump couldn't purge the air and I cranked on it a lot.
did you prime the system at all? I have been told to run the lift pump for at least 10 minutes even when just replacing fuel filters on a 6.7 to make sure all the air is out. At least the power strokes at least have a lift pump to feed the cp4!
I did. I ran the lift pump for quite a while with my scantool. After that didn't work I cracked a line on the rails and ran it again to try to purge more air. The lift pump would flow a lot of fuel but the cp4 would never build pressure.
