Twin lift pumps

[sidedump]

When I was in the Air Force working on mobile generators the MEP series had two lift pumps aranged in series. They both ran at the same time. One pumping to the next pump then to the injection pump.
Would there be any problems with doing the same on my truck?
What do you guys think?

[Turbine Doc]

This one is on my to do list last fall I started the project never finished it have it plumbed for parallel at my frame mounted pre filter, from what I've watched on my gage while heavy towing looks like more gpm not psi is needed which is why I'm leaning toward 2nd pump in parallel manually switched on while towing.

If run all the time I think you would be supplying more fuel than the IP can use extra would just go back to the tank and maybe excess would aerate the fuel in tank with the excess returned fuel.

On heavy tows 18K loaded trailer by EGT, rpm, boost my engine seems to want/need more fuel, my hope is parallel lift pumps will improve this, if not in parallel then maybe I'll try series pumps.

Empty running/non tow a good OEM lift pump provides plenty of fuel.

[markrinker]

Interesting thread. What is the effect of low fuel pressures under towing conditions?

[HowieE]

sidedump
Do you recall if both pumps were the same type and size or were there 2 different types.
I can't think of a reason to run 2 pumps of the same type in series, other than Government waste. If the first punp was a high volume low pressure pump I could see it lifting from an underground tank supplying the finishing low volume higher pressure pump feeding the IP.
If you run 2 of the same pumps in parallel I wouls assume you will also upsize the tubing from the pumps to the IP and not run thre risk of loosing what you hoped to gain in line loss.
Another though. Run the second pump off the boost pressure so it is only running on demand. If you consider this also make sure the second pump is a positive check when off.

[sidedump]

Both pumps were the same and they both ran at the same time.

[Turbine Doc]

Howie I considered upsizing pipe for more flow from what I could gather current dia could handle about 4x of what 1 lift pump could handle if I did my math right.

[rjwest]

I have 2 lift pumps in series, also Press gage on dash

the reason was , i installed a 2nd filter in fuel supply line.

IE: Fuel tank , add on lift pump, filter/water seperator, than OEM lift pump.

The pressure runs around 5-6 psi normal with
add on lift pump off, will drop to " 0"
occasionally on HARD pull. ( turn on second lift pump ) pressure up to 6-9 psi.

With both lift pumps running, about 9-12 psi.

15 psi max at idle.

The gage works great, eliminates any guessing about fuel supply to IP, Also it holds pressure
when eng shuts off ( no Leaks ).

And easy to purge Filters when changing..

? I did notice that when pulling a hill the fuel
pressure fluctuates about 2 psi( constant throttle ), seams to be some bypass flow change, Is this the IP pump.