Gents, I want to offer a fix that has worked for me but is not possible for all, I notice alot of members here that have great concern on the L/P issue. After all the L/P issue will never go away till we re-engeneer the system, DC obviously does not care. When something fails DONT put it back the same way...........try something different.
I firmly believe that the OEM lift pump is an OK pump, but also think that the setup is the problem, NO pump likes to pull a vacumn but prefers a positive head pressure, the OEM setup is the problem, the pump is on a constant vacumn from pulling up to 2 feet and from up to 8 feet away, there is not a pump on the market that will survive this kind of application or punishment. I am sure I will catch some flack over this but IMHO a pusher pump is only a bandaid at best and with 2 pumps you then have twice the chance of failure. I know alot of members are using pusher pumps and some with success With that said once again there is only one fix for this IMO, You MUST install your L/P lower than your supplied fuel source and the less line between the fuel and the pump the better, You MUST also have adequate delivery lines to and from the pump, at least 1/2" line to be safe, some of you may comment that the inlet and outlet of the pump are like 3/8" and that is true but trust me here larger line is necessary in order to supply the least resistance as possible. If you have ever studied hydrolics than you know what I mean.
Here is what I have done to correct my OEM fuel delivery system. I purchased an auxillary inbed fuel tank, this is my MAIN supply to my delivery pump ( no longer a lift pump ) I have installed a ball valve at the bottom of the tank for maintenance purposes and 1/2" line to the pump, 1/2" line from the discharge of the OEM pump to the OEM filter housing in its original location and 1/2" line from the filter to the VP-44.............................RESULTS ARE I now idle at 15 psi of pressure and cruze 75 mph at 15 psi!!! and at wot I can only pull it down to 12 psi!!! As far as fuel usage from my Cummins I have 275 injectors and a comp box, the above stated readings are with the comp on 5x5. Before this mod my numbers were cruze 75 mph at 12 psi, WOT at 4-5 psi.I now use my OEM fuel tank as a storage and transfer tank, I use a small 40 dollar pump for this task, something interesting here is at first I used the oem line from the OEM tank to the aux tank and it took about 30 minutes to transfer its contents up to the aux tank ( main feed ), I didnt like that so I installed 1/2" line and now I can transfer in 13 minutes!!! That tells me alot about fuel delivery lines because the transfer pump and its location didnot change, I simply reduced the resistance of the lines.
I really wish I had a amp load reading from the liftpump from before and after this mod. I know it is less because the pump is not working near as hard now. It no longer is SUCKING.
OK OK, I know that this setup is not for everyone but the same logic can be applied to this concept on the OEM tank as a main fuel delivery system. It is not very expensive and will help alot.
If you dont have an inbed tank than buy a bottom bung tap and come off the bottom of your OEM tank to the pump. This will give you the same concept, The fuel supply must be higher than the pump and the pump needs to be as close to the fuel source as possible.
Bottom line is if you dont want a lift pump than turn it into a supply pump.
Also I had what I thought was a bad lift pump ( crappy psi and down to 2 psi at WOT ) sitting on the bench that had 12k miles on it, just for grins I installed it and guess what I have good readings, so now I have a spare pump for future use.
Cheers, Kevin
