So my F Pump on my 02 is in the tank, someone must have changed it. I would say the dealer but I installed a FP gauge and found that I only had about 7lbs at idle. I decided this was not enough so ordered a new pump. I actually ordered one for the block because I did not know the in tank one had replaced the original as I have only had the truck a month or so. I hooked it up on Saturday and found the new one on tne block would not suck fuel through the tank pump and the tank pump would barely push fuel through the other one. So I decided to hook them both up. Now I have 25-30 lbs at idle and WOT is at least 20lbs. I am thinking that this may be too much so I called Cummins and they said that this was no problem and they (Cummins) hook them up that way all the time instaead of removing the fuel tank to get at the old pump. They also said that the only thing is I may experience "harder starts" as the pressure might float the valves in the IP. I do not have this proplem, it starts great as always and I think the truck is more responsive (power) Anyone care to comment on hooking these up this way?

I have heard of some guys running over 20 psi. But, most run at about 17-18 psi. Anything over 20 psi could teat the diagpham in the VP. Then that is a $1000 bill for replacement for parts only.

Actually from what I heard high pressure doesn't tear the diaphragm it's extremely low pressure that does.

Yeah there is a good thread about fuel pressure and some of the tidbit we all learned about over here...

http://forum.mopar1973man.com/showthread.php/1656-VP44-Write-Up-Minimum-pressure-suggested...

But typically most will suggest you stay in the green.

http://forum.mopar1973man.com/attachment.php?attachmentid=374

C Holmes,Something to think about.Since you now have the pumps hooked in series, and neither one will work adequately alone because of the series hookup, what happens when one of them fails completely?Now that you have two pumps, statistically you now have twice the chances of a total pump failure than you did with one pump.If I were you I would consider relocating the new pump to the frame by the tank and putting in a draw straw.

C Holmes, Something to think about. Since you now have the pumps hooked in series, and neither one will work adequately alone because of the series hookup, what happens when one of them fails completely? Now that you have two pumps, statistically you now have twice the chances of a total pump failure than you did with one pump. If I were you I would consider relocating the new pump to the frame by the tank and putting in a draw straw.

That was my first step in trying to fix my problems...($125 for the big line kit) http://forum.mopar1973man.com/attachment.php?attachmentid=181 But after replacing 3 lift pumps at $200 in under 1.5 years... (Totaling up $600 = $725 total package) http://forum.mopar1973man.com/attachment.php?attachmentid=182 Then 4th pump failed... I threw up my hands and got... (AirDog 150 - $520 - 3 years ago!) http://forum.mopar1973man.com/attachment.php?attachmentid=180 So now... looking back it would of been much cheaper to just jump once and do it right with a known good pump that has a good reputation also a lifetime warranty!

I am running 23 PSI at idle, and it can drop down to 16 on a hard run, once I see 14 I will change the filter. I don't think the truck has ever run as good with the stock pump as it does with the Fass.