Will L.
Well-Known Member
The difference in fuel lube, amounts of moisture in the fuel, etc all has a great deal to do with it.
That is some of the testing we did at the oil/fuel company that was on the 6.5 but was for the parent oil company, not any of the manufactures.
Think of it this way: forget it (injection pump) is anything but a pump. How well within tolerance it was made innthe first place has a lot to do with its life. Then how well lubricated does it stay. If the fuel you are running is better quality in lube and less contamination, the pump will last longer.
The transfer portion of the ip is what suffers from low incoming pressure. Remember Roy on here within last couple weeks was convinced low pressure won’t even allow the engine to run. You didn’t even notice when your LP was dead. The difference is your ip transfer pump was in good condition and his is nearing death. Maybe yours kept pressure more often- maybe you had fuel made from sweet crude instead of regular or sour crude. The base mix of lube into the fuel and if it was refractured to produce it vs single fracture is huge- (almost same gain as conventional oil to synthetic) Maybe less water. Not maxing out demand often can help. Then of course the big one- how many miles on it.
So individual use and circumstances play in.
I associate it to some hummer owners that never had their ect hit 200. Drive it easy, low weight, never bad weather, never hit 55 mph, never tow, etc and they question why so many others have heat issues. Hummers btw loose airflow through radiator starting at 60 mph headwind and the centermount turbo causes more heat into the rear of the heads.
When the group of us guys tested the lift pumps, there was a couple of exceptions to the rule- one AC Delco ran amazing and after running non stop for over 14 months- barely lost any volume/ pressure. That pump got installed on his personal truck afterwards and ran great till he died. His grandson got the truck that guy put another 100,000 on it after that, then I gave the truck a once over before he moved away it was still pushing 9psi! However, the other 4 of the same part number all died pretty equally.
If yours is performing well- GREAT! but this is why I say monitor it. A guy might have 2 trucks and installs identical LP, bought at same store on same day. One makes it 6 months, the other 6 years. When that incoming pressure drops- it wears the ip faster. Maybe a person got the magic LP and magic ip where the LP lasts a decade and the ip barely suffers before it gets discovered.
But for every super lucky guy, there is a super unlucky guy - outliers tend to work that way.
as to the larger diameter line in to ip- do the math how much fuel a new dmax or cummins actually burns and ask yourself why all the best lift pump manufacturers run 1/2” line.
The DS4 on my 1995 would simply quit if the lift pump wasn't helping it overcome the fuel system restrictions. (My DB2 would loose power with a failed lift pump as the housing pressure was referenced off the inlet PSI.)
