Replace cp3 or fpr

56taskforce

Well-known member
Mar 30, 2014
1,081
56
48
Although it isn't running bad I am thinking my CP-3 is getting weak. I have no way as of yet to check rail presure but before I put the lift pump on it was falling on its face. When I added the lift pump got a huge performance gain now that gain seems to be going away. Kind of thinking the CP-3 was on its way out and the lift pump was a bandaid. Maybe I will go with EFI Live now and do some data logging.
My truck has 170,000 on it
 

Robby Avery

GM TECH @ FENDER GMC
Jul 31, 2008
820
2
18
Norman Park, Georgia
56taskforce if it seems to be going away when was the last time you changed you fuel filter if the filter is clogged or clogging it will feel like the truck has less power due to lack of fuel casing the rail pressure wot be lower than normal and thus the feeling of less power can be felt if that's the case but if not before you drop big money on efi two investments will help you a rail pressure gauge and a fuel pressure gauge one will show if the other is suffering just me two cents
 

56taskforce

Well-known member
Mar 30, 2014
1,081
56
48
Filter all changed with the addition of the lift pump. The two that came with the pump and new Racor. The DIC still says 78% for the fuel filter.
At the same time I did the lift pump I also added both PPEs ported rail and CP-3 inlet fittings. That may have been part of the unexpected performance that came with the lift pump. I will add it only falls on its face WOT level 5 and I did limp the transmission once after the lift pump but hasn't happened again.
The reason I was thinking of doing EFI Live for data logging the rail pressure is it is in my build plans anyway. I was waiting to build the transmission first but I kind of want to know whats happening is it the CP-3 or the transmission protecting itself? It isn't throwing any low rail pressure codes or trans code since the one time it limped.
 

catman3126

Ehhh?.... You don't say?
Jul 24, 2012
2,636
0
36
NE Oregon
check the return rate from the CP3 return line. if it returns over a certain amount at idle then you will know. do a search and fine the test procedures.
 

56taskforce

Well-known member
Mar 30, 2014
1,081
56
48
steve86 didn't mean to high jack your thread hopefully my problem will help you out as well.

Thanks Cayman I will look in to that.