Last fall my truck started my truck started experiencing symptoms of VP44 failure. My truck is a H.O with 142xxx miles. What happens is after driving it for a period of time longer than say a half hour and shutting the truck off, if I would try starting it again about a half hour after it was off the CEL would come on. The truck would idle fine but when i go to hit the throttle it revs to 1400 RPM uncontrollably, it feel's like its either giving it the amount of fuel it needs for idle or WOT, no in between. It also won't rev pass 1400, I'm assuming that is due to reduced power from the CEL. So the truck would be idling fine for a while and then it would just cut out randomly. I could then start it again and most of the time it starts and the throttle acts normal again. If I go on a long ride and then let the truck sit for an extended period of time (5 hours or so) this doesn't happen. In the winter this issue wouldn't occur except for once when I went on a 2 hour ride.
I think the electronics on the pump started to go and when they overheat something shorts or opens and it doesn't allow for proper fueling. Now that its closer to summer and its hotter out this happens more often and some times the truck won't cut out when idling (I've had it idling for 20 minutes or so and nothing happened) and doesn't return to normal unless it sits for an extended period of time. The codes shown are 1688 and 1689, internal injection pump failure and failure to communicate to the ECM.
Whats strange/frustrating about this is that when it does run normally it runs perfect so its hard to believe its the pump. What leads me to believe it is the pump though is last summer when i got the truck the fuse in my power circuit for my FASS went out and i drove without a lift pump for probably around a week without noticing. Now I always make sure to listen for the lift pump to run on ignition on and have since installed gauges (constant 17 psi fuel pressure).
Any thoughts on ifthis is the IP would be appreciated