The pumps are not referenced to atmosphere, they each increase the outlet pressure so many psi above inlet pressure. The pressures will stack, in fact they will more than stack. Check out my thread.https://www.dieseltruckresource.com/...ht=arithmetics

 

I got the "stacked" result when I put the P4601HP in line with my LP which was giving 18 psi at idle, It burried my 30# guage and found a weak spot in the LP gasket which sprayed diesel all over the engine compartment.

 

Hi 7941 and Jenks
It crossed my mind about having two pumps,would it increase pressure at the vp44 or not.Thats the reason I`m going to fit the vulcan line kit,presumably bigger the line more volume less pressure.Anyway I`ll find out in a couple of weeks when everything is fitted.

 

I just put on the vulcan big line relocation kit with a new cummins lift pump about a month ago and i have 16 idle, 15 cruise, and 13-14 wot. Excellent kit and very easy to install. With these numbers i dont see any reason for a extra pusher pump.

 

I put the "update" in tank pump in August. I have 10psi at idle, as low as 6psi WOT. Can a holley pump or other inline pump be used with the in tank pump upstream rather than the old lift pump downstream?

 

I believe some have done this exact thing. I sure would.

 

The original lines on the tank unit hard plastic, what is the best way to connect to these? or can I connect directly to the tank fittings? What are "-6an" fuel lines?

 

I was able to direct connect -6an aeroquip line from summit directly to the oem tank connector. The hardest part is trying to disconnect it from the tank, then remove it from the oem line and plug in your -6an line. You may have to lower the tank.

 

Sorry to be a pest, To clarify, the plastic elbows on the top of the tank unit that the factory lines clip to are removed and then an 6an fitting is threaded into the tank unit, or do the 6an lines connect to the exisitng elbows?

dw

 

I did the same with mine, with out the spray. WOW, 29psi at idle and 19 wot. also threw in some 3/8" line from the hard line on the fram to the old lp. works great.