LP upgrade.K3500 93 HO pump. I get it but...

[aquaman0001]

Is there a down side to installing a LP made for a DS2 IP onto a DS4 IP? Does the DS4 pump need as much fuel as the DS2? I was looking at a Delphi pump chart and wow. The FP905 delivers 35GPH and 9.5-14PSI. Am I just dumping more fuel back to the tank? Is that a bad thing? Also, I had my leaky return lines replaced with viton since I run a bio blend. The return lines are not clamped on but my mechanic said there is so little pressure on the lines it should not be an issue...Uh. does this sound right?
Thanks for any comments or suggestions.
A

[DmaxMaverick]

First, there is no "DS2" pump. The DB2 pumps are mechanical, vs. the DS4 electronic. I am not aware of any difference in the electric LP's, of any year.

The return circuit should see little to no pressure. It should be unrestricted to the tank.

14 PSI seems a bit high. However, it may just be the extreme rated static capacity, which often includes conditions you won't/can't recreate. Typical max supply pressure on any 6.2/6.5 is 4-8 PSI, dynamic (engine idling). Any pressure above 1 PSI is sufficient. The only requirement is a consistent supply to the IP at all demands (it should never be negative). The fuel transfer pump (built into the IP) will draw fuel from the tank with a failed/missing lift pump, although it may decrease the service life of the IP, absent the lift.

[aquaman0001]

http://www.dieselplace.com/forum/att...2&d=1173301445

[JohnC]

The DB2 pumps use housing pressure to control injection timing. I think this is why the DB2 lift pump is spec'd for a higher pressure. The DS4 pump has a pressure relief valve that shunts excess pressure to the return line. Any excess pressure capability of the lift pump will just open the relief valve and get bled off.

I think if you look at the volume spec you'll see they are about the same.

[aquaman0001]

That's what I needed to hear.
Thanks Guys.