Two fuel pump in serie

I have essentially the same set up on my car. Many racers do also and will just use the electric pump to prime the carburetor(s) to start the car.
Even the stock mechanical pump is enough to run the car even under race conditions.
Where it helps me is to fill the carbs when the car has been sitting.
Just turning on the ignition key will have the engine primed in 3 or 4 seconds.
In my case, the Pantera-Electronics Engine Controller will then turn off the electric pump and turn it back on as the engine needs it while it is running.
The electric pump is also useful on a hot engine under certain atmospheric conditions (weather) to prevent fuel vapor lock in the fuel line.
The Holley red pump (shown in the picture) is the low pressure pump set at 3 to 4 psi output. That you would use for Weber carbs. The Weber carb(s) is designed to run at that pressure.

The blue pump would be for using with a Holley carb since it is set at 7psi. The Holley is designed to run on that pressure.

The Holley carb needs to be kept wet to keep the fuel bowl gaskets from drying out, shrinking and cracking.

The Weber carbs do not but because of their design, the fuel in the bowls evaporates quickly (about a week or so). They have no gaskets submerged in fuel to dry out or crack.

Leaving the engine sit for a week, the electric pump helps a lot in reducing the stress on the starting motor and mechanical pump to turn the engine over long enough to get fuel into the carburetors.

I this case it appears the electric is before the mech pump ? I dont think the electric can pump thru the mech pump with internal check valves ? As Doug said the mech pumps depending on what you have installed will give you what you need in GPM by far more then you will ever need ... both electric and mech have pro's and con's I prefer mech pump for safety reasons ... unless of course you are running some sort of exotic fuel induction system like webers or EFI ... My 2 cents.

Ron, it definitely pumps through the mechanical. In my case I have the Holley mechanical in there too.

The Holley electric pump is one of the quieter units available but it can be annoying to listen too for sure.

I think more times than not, the decision is based on that sound issue alone?

Even so, if you just had the mechanical and you let the system run dry, you just need to turn the engine over more so to get everything primed.

For me, that means maybe the battery is not charged enough to do that more than a couple of tries?

In the end it comes down to personal preferences and sometimes previous experiences whether they be good or bad.

The point about safety on an electric pump without a safety shut off device REALLY comes home to roost if the scenario is an unconscious driver in an upside down car? Holley does have a no oil pressure safety switch to plumb into the engine and wire into the pump.

It's cheap but even so, how much is your life worth? A lot more than the cost of the automatic shut off switch.

It is an excellent idea for anyone running an electric fuel pump. I agree on that 100%. You have to have one.

... Problem with electric pump is it has to be below the fuel line otherwise it looses prime. My efi AC has the pump below the gas tank behind the driver seat and if isolated properly with vibration isolator the sound is minor. Being in the pump business I just don't see the need for two pumps ... We don't use a booster pump before a constant volume pump

So far I have not run the carbs dry with the electric pump off. Maybe I'm not trying hard enough? LOL!

The fuel pressure gauge is right there in front of me too!

I agree, the mechanical pump has proven enough even with all the abuse I could concieve on giving it.

The sole purpose to me of the electric pump is for priming reasons. That's it.

I will grant you that I put the electrical in there to fix a problem...theoretically that is. It turned out that there was a rust pinhole in the steel pickup tube in the gas tank about 1/2 way.

I of course thought I knew exactly the problem, not enough pumping capacity? Of course I was wrong. Par for the course around here?

I will say though that you definitely don't want to suddenly run dry at WOT. Been there, done that. For one thing, IF you were running with mufflers, they won't be there anymore. The magnitude of the backfire from suddenly running lean will either completely blow up the case or at a minimum blow a nice big hole through them.

Should that happen, pray that the shrapnel doesn't kill or maim anyone. I got lucky. Just went temporarily deaf for a few hours. Permanently stupid though?

ELECTRIC fuel pressure gauge is here. Can't miss it...now...sure!

Sig you have a Holley so I doubt you will have problems with the float bowls, and as accobra says you should just run one pump. Doug's setup is different and works well for him. I would run just the mechanical pump and remove the electric pump, it could be the electric pump is also wired off the ignition coil feed giving you other pains.

Doug I agree on the lean condition is not good and is definitely going to leave a mark..Nice Gauge set set up ... is that done with a diaphragm ?
Ron

No diaphragm. There is an electrical sensor plumbed in line between the Webers. Expensive gauge but worth it.
The sensor is high tech. Cycles something like 300 times per second. Any changes in fuel pressure show instantaneously.
It's a good way to monitor F/P in a Pantera reliably for everyday or EXTREME situations.

Many thanks for your comments. I will remove the electric fuel pump during next weekend. I should probably empty the fuel tank before since the fuel connections are at the low point....

Hartwig

Ah my race car had fuel guage line and diaphram filled with anti freeze and diaphragm was mounted in the engine compartment and the other side of the diaphragm was tied into a fuel line I guess the object was to keep fuel out of the engine compartment

SIG ... depending on what hose was used sometime you can get away with gently crimping the hose with a vise grip pliers to remove the pump.

quote:

Originally posted by accobra:
Ah my race car had fuel gauge line and diaphragm filled with anti freeze and diaphragm was mounted in the engine compartment and the other side of the diaphragm was tied into a fuel line I guess the object was to keep fuel out of the engine compartment

Ancient history, diaphragm is with a mechanical gauge, as you said to keep fuel out of the cabin.

This gauge is 100% electronic. It uses a special pressure sensor, much like an electric oil pressure gauge does. It actually has it's own wiring harness since there are options with the gauge such as low pressure warning, downloadable data, etc.