Ok my buddy has a 2006. His truck is set to stock. It is hard for it to crank. He has to turn it over, over, over, over, over, over, and over forever. After you let it run a while then try to recrank it sometimes it cranks right up. If you let it sit for a few minutes it is hard to start again. He had an injector go bad. He replaced that. Thought the lift pump was bad. He replaced that. Thought the FCA was bad. He replaced that. Still it will not start everytime. Return is even blocked off. So, all fuel is going through the pump. While starting it shows 1200psi at the rail. Then when it is idling it is around 7000psi. Every injector was pulled and checked for cracked tips. The truck has 125000 miles. Every injector tube was pulled individually to check to see if it was an individual injector causing it to loose pressure and not crank. So, What do you think is wrong with it? CP3 going bad? The only thing that is weird is when it does crank it runs fine. Also, all of this is in a warm building. So, not due to it being cold outside. My guess is CP3, but I thought I would let everyone on here take a stab at it. Thanks in advance guys.

 

dont believe thats enough pressure at the line it should be around 5k

 

It is a bad practice to block the fuel return, that results in pressure unbalance that distorts the case and can blow the O-rings between the two halves of the CP3 and result in low pressure.

With initial low pressure I suspect that to fix the problem he may only need the relatively inexpensive seal kit that is used to fix the case leaking problem, and they are easy to install.

 

He only blocked the return to try and see if it was sending to much back to the tank. He only done it for the troubleshooting. No one thinks bad CP3?

 

I suppose I better ask what you mean by hard to crank. Do you mean that it turns over slowly during the cranking process?

If that is the problem, your starting fuel pressure will be too low and it will be difficult to start. If that is the case I would check batteries, cables, grounds, starter solenoid, and starter itself.

If it turns over fine, and initial starting fuel pressure is low, then I would carefully listen to each injector with a stethoscope to determine if one or more were making unusual noise before tackling the pump. All it takes is one injector to start leaking off to lower the rail pressure enough during starting to make it very difficult to start.

I have no clue why anyone would pull the injector tubes to check for a bad injector, because unless you have a test bench you are just wasting your time.

By 2006 very few of the notoriously dud CP3 pumps were still in production runs, so unless there is wetness at the bottom of the pump where the front and rear halves join, I would not think it is the pump.