Low fuel rail pressure - searching for root cause
Started out with a fresh OEM Delco fuel filter before this trip. (The old filter lasted all winter - even through the December snap of -25F cold, without plugging. Thats a first.) Fuel level full to 1/2 tank during episodes described below, no blockage of OEM tank mounted fuel cooler/radiator.
About 1500 miles into the trip, I noticed the check engine light on. Checked and reset a 'low fuel rail pressure' code. Started watching the requested vs actual fuel rail pressures on the Edge.
Sure enough, with a stiff and gusty head wind working against the tall, shrinkwrapped boat - any hill ascended with even a medium heavy foot to maintain 60mph would predictably set the code. All of this happened while running the stock OEM tune, water temps were never over 200F, trans temps 200-220 max the whole time.
Hmmm...pulled over and looked at injector return rates at idle...nothing looked out of range, nice quiet idle, and the truck is otherwise running fine by all 'seat of the pants' measurements, until the code is set and the truck then starts running 'lopey' and low on power. When I started back at it, began watching fuel temperature. Normally it runs about 130F-150F, but today for some reason it was in the 160-170 range? All this on a sunny 75-80F spring day, Wisconsin rolling hills, with about 15K# of boat and trailer in tow...nothing out of the ordinary, really - except for the headwind.
When running the next hill, I kept my foot moderately into the throttle, watching fuel temperature...when it went past 170F and about when it hit 180F, the requested vs. actual pressures began to separate, and then *BING* the check engine light would illuminate, and the truck would start running badly. I repeated this cycle a half dozen times. There appeared to be a direct relationship between high fuel temp, and low fuel rail pressure. At one time, really pushing it - I saw fuel temperatures of 190F...that doesn't sound good!!!
Later that afternoon, it began to rain, the outside temperatures dropped to 60F, and the headwind and hills went away. No more codes, power felt better, and I could again easily hold 65mph with 160F fuel temps, no codes...
Whats making my fuel get so hot? Is my injection pump on its way out?
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