Two fuel pumps? WTF

[Adams1stCuda]

Continuing in my free time to go over my wife's car (72 340 Cuda) and have discovered that it has two fuel pumps; the OE engine mounted as well as an electric mounted under near the tank.  Also, the electrical on the latter is atrocious.  Wired to the batt terminal on fuse block directly (not fused) to a cheap on/off toggle in the forth hold on the dash.  Evidence of overheating at both the fuse block and switch...scary.

With the circuit being independent of any switched power/relay if its on it runs while the car is off.  Pushes past the OE pump and leaks into the carb.

First, why in the world would anyone ever decide to do this?  Second, what should I do?  Remove/bypass the electric pump and see how the newly replaced OE pump handles or the opposite? 

From my understanding the engine was relatively recently rebuilt with a small overbore and a single step up cam.  Carb is a Holly 600 w/ electric choke (also directly powered from the acc terminal of the fuse block...at least its fused).  Carb was eval'd and re-jetted.  To the tech, seemed in good condition and didn't need a rebuild.

So very glad we got this car at a very reasonable price...looks like I have some work ahead of me to get it running reliably/safely.

[1 Wild R/T]

Probably added to help when starting... Since with current garbage fuel there are allot of cars that you need to prime in order to start.. Switch the pump on till it fills the carb then switch it off & drive as normal... For many wiring relays appears to be some kind of black magic.... Simple & worthwhile but black magic..

[Brads70]

   I'll be installing one on my buddy's 71 Hemi Cuda clone. He doesn't drive it very often and it takes forever cranking to get fuel into the bowls.

[RUNCHARGER]

That is my guess as well. On a Hemi anyway the AFB's evaporate the gas in the bowls within a day or two. So you install the electric pump to prime the carbs. No excuse for unsafe installation though. Probably best to remove it and replace all rubber fuel lines and clamps and check the condition of the metal fuel line as well.

[Topcat]

God how I do know that!

I fire mine up if not every week then every other week.

Leave the electric where it is if you want.
Just bypass it and it's there as an auxiliary back up if ever needed.

[Adams1stCuda]

So a couple additional things.  If I leave it, does it then become more work for the OE pump to pull fuel through the electric pump that is off?  Second, it will run and generally drive without the electric on, but it then has a tendency to stall when coming to a stop...doesn't do this with it on.

Also, what should be an approximate fuel pressure at the gauge between OE pump and carb? 

[Shane Kelley]

Fuel pressure for a carb motor is in the 6 psi range +/- 2 psi.

Myself. I would remove all that electric pump stuff and clean up the wiring and fuel lines. Just another area of potential problems. 

I guess as others have stated it could help with starting after it sits for some time. But a good mechanical pump will get the carb fueled up pretty quick with just a few revolutions. Edlebrock and Carter carbs seem to be the ones that always have empty bowls from sitting.  The Holley style ones don't seem to have much of a issue.

[HP_Cuda]

Heck if it's not a liability (bad setup) then I would leave it and clean up the wiring and add a fuse. Otherwise if it looks like garbage and runs like garbage I'd rip it out.

[Burdar]

You can pull fuel through some electric pumps but not all of them.  If you want to run an electric pump just to fill the carb, I would plumb the pump parallel to the main system.(not in series) The electric pump should push fuel through the mechanical pump just fine.  You could take it a step farther and run the pump off of a relay that only gets power for a few seconds once the key is on.(no toggle switch to worry about)

[Adams1stCuda]

So I believe I am just going to take it out of the equation first and see how it runs and if needed properly wire it and plumb it in parallel.  Also going to inspect all lines and replace as needed.

[YellowThumper]

My  is to have all manual or all electric. I would not want to pull fuel thru pump. Also would not want to pressurize back side of manual pump. Adding a bypass so fuel is not pulled thru electric would require a 1 way valve or you will just pump fuel in circles at the pump.
If not a Shaker it is easy to prime carb manually prior to startup. Myself, I just crank car for a bit with no throttle pumping. Stop and wait for a few seconds. Give it a few pumps and crank again. Works well.
All or nothing is my vote.

[73440]

I'm using Carter carb and just take filter off , squirt a little gas in it , if not driven in awhile.
Wish it was different routine, but that's gasohol for ya.

[YellowThumper]

I'm using Carter carb and just take filter off , squirt a little gas in it , if not driven in awhile.
Wish it was different routine, but that's gasohol for ya.

This/\/\/\/\/\
Gas is not what it used to be. Heat from the old engines just forces the evaporation of the new blend.
Just need to adapt because it aint gonna change.
My stated routine is with my "other" car. My challenger has electric pump with return line. Still with carb for now. I fire up pump for a few seconds and car starts without any hesitation now.