What are the psi's for the 2?
I can't see why anyone would go to all the trouble to put in something which only puts out 8 psi...

 

the 391 puts out about 65 GPH at little over 105 psi

the 392 puts out about 85 GPH at right about 145 psi

that's @ 12 volts. Both drawing 13.5 volts will give a little more.

I said it was similar to the OEM pump because that's what walbro says about the 391.

 

It is my understanding that the psi is really determined by what the spring settings are set at in the return valve. You can run as much psi as you want, but you will probably never need more than what they are set at already. Mine is about 18.5-19psi at the cp3 at idle...after going thru the stock filter housing and thru the 2 micron remote mount kit...and back to the cp3. I think mine will pull down to about 16 at WOT. The Walbro pump is small in size but very capable. The 391 pump will probably provide all the fuel and then some that our trucks could use. But like was said already, why not go ahead and get the 392 for a few dollars more.

 

With the GDP, you don't have to connect any fuel lines to the tank...correct. Just tap into the existing lines where you mount the pump? I have an '03 so my OEM fuel pump is at the fuel filter, not in the tank. It looks like you just cut into the existing lines.

 

That is correct. On 03-04.5 trucks you DO NOT need to drop the fuel tank unless they have had the dealer install the In-Tank pump under warranty. You can just cut into the metal supply line and pull fuel from there.

Coincidently, when me and some buddies installed mine we did drop the fuel tank........but only because I was doing the Vent Tank mod and exposed barbed fittings mod at the same time. I can fit about an extra 5 gallons of fuel in my tank now and that increased my cruising range up to 700 + miles.

 

I have the in-tank pump. Why doesn't it work with that setup? Will the stock LP inhibit the flow? I'm either going to install the Glacier system or perhaps a FASS in the next couple of months but I get confused which is the best (most reliable) option.

You guys do some good work! I'm just going to show this thread to my Cummins tech and say, "make it look like this". I'd screw it up for sure.