97ramctd

my truck has been ticking. eliminated it down to the lift pump or the overflow valve. was told i needed to get the pressure checked after the lift pump. i was told i could drill and tap the banjo fitting on the pump. so i did and at an idle i have 18-22 psi not real sure exactly what it is it bounces between there. running down the road just crusing 55 it has bout 18 or so... floor it and it slams down on zero.. lift pump toast? thanks

kawi600

You should see 24+ psi at idle and 32+ at 2000rpm no load I believe. I had a pump that did what yours did, dropping pressure a lot under load and it was the lift pump.
Be careful those gauges with a remove electric sender arent always very accurate. Taking a measurement with a fuel pressure gauge tool is a good idea. Youll need to install a needle valve to restrict the pressure pulses or theyll quickly kill the sender.

XLR8R

Weak lift pump has pressure under light load, but not enough volume to keep up with a heavy foot - so gauge drops to zero.