Lift Pump Regulator

[AsphaltCowboy]

Just finishing my Suburban 6.5 swap. Used a lift pump I had left over from another project. As I suspected it ended up being too small. Runs fine at low throttle but put your foot in it and there's just nothing there. That pump was only rated for 5psi and I'm not sure if it was even rated for diesel.

I'm planning to buy a Walrbo 392 and use a regulator and keep it around 15PSI.

My question is, can I splice the regulator return line into the stock return line that runs back from the injectors and IP? Or do I need to run a new line back to the tank? I'm trying to avoid dropping the tank and adding a new fitting.

[DmaxMaverick]

Just use an OEM/Delco pump. System pressure is only rated 4-8 PSI (any pressure above zero is sufficient), but that means nothing if flow can't be maintained. 15 PSI is too high (not that it won't work, but is out of spec by near double). Flow is key, and pressure has no real value as long as it's positive. You're talking to the wrong end of the horse.

[Dvldog8793]

Howdy
I tried this idea once. Nothing but problems(leaking fittings and filter) and no improvement.
IMHO best option is stick with the factory style by a GOOD manufacturer. Kenneddy sells known good pumps. If you live in the SALT belt make sure you really seal up the electrical connections and also give the pump a coat of cold galvanizing paint. My pump failures have been due to the pump housing rusting through and not actual pump internal failures.
Fuel line fitting should be coated after tightening up and verifying that that everything is dry.

DMAX is 100% on.

[Kennedy]

Back in the day I ran a Carter HP rotary vane type pump on my 6.5 Figured I'd take care of it once and for all. Not

When the pump quit the truck wouldn't drive at all. Thankfully I had enough stuff to bypass the pump. The rest of the days of owning that truck was with the AC delco pump on the rail. No big lines, opened up filter head ports or anything. Wasn't short on power or missing anything in my opinion.

[Robyn]

i agree 100%

Volume is the key word as Maverick mentioned.

The lift pumps job is just to maintain a good volume of fuel to the transfer pump in the IP.

The lift pump also allows for an easy way to refill the filters and lines if the filter is changed or the tank run dry.

The DS system is designed to move about 40 gallons per hour through the IP and back to the tank as part of the cooling process for the PMD and the IP itself.

The transfer pump does the majority of the work, it just needs a little help to keep the fuel at the inlet is all.


As mentioned, stick with a stock AC Delco replacement, Or OEM quality.

If the box says MADE IN CHINA--- pass and move on.

[AsphaltCowboy]

Thanks for the input. I understand that flow is what matters however if a regulated pump can deliver a constant 15psi(or whatever the optimal number is) then the flow will always be there. I just figured a constant pressure would be best.
I think I'll order an OEM pump and see how it goes. Might also try removing my pre-lift pump filter and see if that makes a difference. Or just hooking up vacuum and pressure gauges to see if either of the filters are creating a notable restriction.

[AsphaltCowboy]

I put a pressure gauge on the line between the filter and IP. I'm getting about 4-5PSI at idle, 4 at steady diving and no less than 3psi at WOT. So it looks like I'm getting plenty of fuel. Guess I'll have to look somewhere else for my low power problem.

[AsphaltCowboy]

Still haven't had a chance to get clear hose yet but I did do a couple experiments with interesting results.

First I tried bypassing the filter before the pump. So it went tank>pump>secondary filter>IP.
I took it for a test drive and sure enough it ran noticeably better, more responsive and more power. I was not super surprised, I figured if anything was creating a problem is was the filter before the lift pump. Fuel pressure was also unchanged during this test.

Next I tried also bypassing the secondary filter. I did not expect this to make a difference but did it out of curiosity. Now it goes Tank>pump>IP. No filter anywhere in the system.
I took it for another test drive and it had even more power this time. Much more responsive, especially right off the line and more power. It was now running fairly close to what I'd expect.
I re-plumbed it to eliminate the secondary filter and place the water separator after the lift pump. It runs ok like this but still nothing like when both filters were eliminated. I will leave it like that for now until I can figure out a permeant solution.

I still need to test for air but at least now I know it is for sure a fuel problem that is causing my issues.