Just out of curiosity, can the CP3 loose it's "oomph" over time? Can it wear out I guess is a better way of asking? Reason is, is that at times I notice my RP isn't quite what I think it should be. Upon first startup of the day it will easily run 12-15k psi with little effort. As the day wears on it sometimes won't get much over 10k psi while running down the highway.....even under WOT at that point it seems to struggle to build close to 20k psi.

I know the '03 trucks run a tad lower on RP but my pressures just seem a bit too low. Is my pump worn out or do I have nothing to worry about?

 

I would suspect a weak high pressure bypass valve. You can get a bypass block off plug from genos. Once plugged see what your readings are.

 

Most common problem for me when this happens is a bad connection on the high pressure sensor running to my gauge. Disconnect and reconnect, see what you get. If it stays low you may have an injector issue getting ready to start or other related high pressure issues as stated above.

 

I guess you believe your $10 gauge more than the seat of your pants.

Don't go fixen what ain't broke!

 

Just had the injectors done by Don back at Christmas time. Readings are the same on the gauge as before. I'll try disconnecting/re-connecting and see what that does.

 

Are you talking about the relief valve on the rail? I was under the impression that blocking the relief port was a no no. I know you're talking about doing it just to test it but can anything be seriously damaged by doing this......say under WOT to check the pressure?

 

Unplugged the connection and re-connected......same readings. Guess I'll try the rail plug and see if anything changes.

 

Your are correct. The relief valve gets weak after a period of time, especially if your running higher pressures. The only way to actually diagnose it is to block it.

 

Thank you sir....I'll give it a try and see what happens.

 

Hvytrkmech's advice is spot on.

You are correct that the current conventional wisdom is to not run the plug for fear of blowing up injectors, but you do need to use the plug to properly diagnose. And that is the cheapest troubleshooting route at this point.

If you still see the same numbers on the gauge, and there is no discernable loss of power, well of course then the pressure sensor is known to go bad as well. But they are $$ so maybe if you can have a shop check it and the gauge as opposed to just replacing.

As far as the cp3 goes, while it is a pretty hardy unit, it isn't infallible. They do tend to wear down over time... just like the relief valve does.

Now if it is the relief valve that is the issue, usually they prevent you from seeing the upper end pressures, not necessarily leaking at the low end... although it can be progressive. It is hard to do internet troubleshooting.

If a new relief valve is required, TCdiesel sells them in different relief points and are rebuildable.

 

Thanks for the clarification mr. zoo. Very thorough.

 

I did forget one thing...

While at idle, you can disconnect the wiring plug at the FCA and the cp3 will go to full commanded rail presure and you should read between 24-26k psi. What you get will be a clue... if you have the rail plug in, disconnect the FCA plug, and see that 24k+ psi on your gauge, you are done troubleshooting, replace the relief valve.

 

Geez....it's so easy to overlook the simple things.....forgot all about unplugging FCA to check and see if the gauge reads max pressure. Thanks again.

 

No worries... I sincerely hope that is all it is.

 

It's not causing me any issues but anytime something ain't what it's supposed to be I have a tendency to hunt and hunt and try and find the answer......in other words.....it drives me nuts!!!!! Hopefully it's a simple fix.

Thanks.