Actually the in-tank pump was implemented for that very reason: To allow the CP3 to draw it's own fuel in the event of lift pump failure. It's a flow-thru design. Many electric pumps are.

Having said that however, I would want to examine it's flow capability before trying to draw high volumes though it with a FASS or similar high pressure/high flow pump. Probably why they have the draw-straw stuff. You can only pull so much though a given-sized hole.

 

That was my point, I guess I should have typed more!

 

if the cp3 can draw its own fuel what is the purpose of the in tank pump other than a primer? I under stand it's for more demand of fuel but as my truck wont idle much less pull its own weight i don't see how this is true

 

The CP3s on some of the smaller diesels don't use a lift pump at all. You should read this thread:

https://www.dieseltruckresource.com/...d.php?t=227652

 

The CP-3 can't draw the needed fuel thru the existing lines to supply the demands of the stock HP, let alone any enhancements. The in-tank pump is there to supply the speced 4 psi pessure to the CP-3 that it needs to supply rail pressure plus adequate lube\cooling flow.

Generally when the in-tank pump dies so does the engine. There is enough restriction it won't pull fuel. Very occasionally you will find one that will run with a dead pump but its the exception rather than the rule.

 

I wish there was some way to verify this, because I've heard different. That would seal my decision to add a standby/helper pump.

 

If you are willing to spend close to $400.00, why not spend $99.00 more and get a Airdog and have a lifetime warranty? It costs a little more but I am very pleased with mine.

 

Because it adds alot of unnecessary complexity to the fuel system on a basically stock truck and comes complete with a set of headaches all it's own. You just haven't had one yet.

 

My truck is basically stock and you are right, I have not had any headaches with my Airdog other than the morning after I installed it. It was so easy to install and took so little time, I had to much time after the job was complete to consume to many cold beverages Im not sure what complexity you are talking about. The Airdog just basicly replaces the crappy fuel system that was put in these trucks from the factory.