Well I new it would happen again but I did not expect it this soon. Today I dropped the truck off at the dealer for a new lift pump.The factory pump gave up at 67000 now this one at 89000. Changed the filter last night and today it was still pulling the PSI down to 4-6 when I put my foot in it.
I still have 9000 on the warranty so it should not be a problem. But the dealer gave me the old routine about “if its not covered under warranty how much it will cost and that if I decide to fix it myself that there would still be a $76.00 fee “.

This brings me to my question what else could cause the fuel PSI to drop off like that? Also if the dealer says that every thing is OK and the PSI is still low then what?

 

I would do the volume test as DC describes... Check out this post...

https://www.dieseltruckresource.com/...threadid=67091

 

Just an update on this problem. The dealer just called and the pump is putting out 47% of rated flow. DC will not replace until at 40-45% in the dealers words “run it until it blows”. I tried to save DC some $ but it seems that they had rather pay for a lift pump and injector pump instead of just a lift pump. OH well.

 

There is a minimum flow rate. If it's flowing less than the minimum then it's time for a new lift pump. If it's flowing greater then the minimum I wouldn't worry about it. When they say 47% of rated flow what are they referring to. I would find out.