Originally Posted by wannadiesel

The fuel pressure is 16 psi at idle, varies between 12 - 17 at cruise, and will go as high as 18 when engine braking. I have dragged it down as far as 6 psi on WOT runs.

A healthy diaphragm pump makes 7-8 psi at idle.

Top end "felt" better.

I don't think high inlet pressure would change the timing curve assuming that the stock LP was keeping up. Remember that there's a vane pump feeding the pump internals, that's what makes the pressure inside the pump housing. That vane pump is going to tend to isolate the housing from any change in inlet pressure, assuming that the vane pump is kept supplied with fuel at some pressure. I don't think it matters if it's 4 psi or 14.

Originally Posted by boomer

Wana, I used to have a piston lift pump on my truck. Pump sprung a "serious" leak while in Tampa, FL. Had to have pump remaned there. They told me that the piston lift pump was the problem. They said anything above 12 psi was too much for the VE pump. This was at a pump reman shop, not a dodge dealer. This was a stock pump. Cost me $1200.00, 4 days car rental plus 4 days in a motel.

Originally Posted by bgilbert

This doesn't mean nothing. Your pump could spring a leak anytime. Over time it probly would've started leaking if you still had a stock lift pump. Don't read into what ANY shop says about our old trucks. Most have no clue about the old trucks. They are still going on what they learned in 85 etc. This low pressure lift pump is designed by Cummins to be used WITH a VE pump. You did have the low pressure piston pump yes, and not a 2nd gen piston LP??