First off the ol' vp44 went out on me and I had a Raptor lift pump. New vp44 installed and a new airdog 150 and initial results were great! 5 mpg improvement as long as I didn't lay into it. Well the other night I went out for a run and started the truck, backed out, then thought I should check my lift pump to see if it was still running. (Gauges ordered and on the way). Shut it off and bumped the ignition and nothing. The airdog relay clicked under the hood about 5 times and nothing. I wait several minutes and bump it again and it works fine. I keep bumping ignition to make it run and it does. Start truck. Turn it off. Bump it and nothing. I read somewhere that the ECM could be on it's way out the door and I might have to wire a switch into the dash. Does anybody else's truck do this? Will the lift pump not run for a set time after truck is off?

 

I have a Raptor and it does what you are saying I believe because the pump cuts off when the pressure reaches a certain level. So if you turn the truck off and immediately turn the ignition back on the system is already up to adequate pressure so the pump doesn't turn on till the pressure drops.