Fuel pump

[Don Henschel]

What is my electric fuel pump? I spin off the star nut on top of the air filter and trickle in half an ounce of gas and tighten down the nut and close the hood! This usually starts the car and I might add my 50 Mercury Sport Sedan is still on 6 volts! Those flathead V8 fuel pumps have a very short stroke, low volume and pressure and will not fill a dry carburetor by cranking on the starter. I'm going on 40 years of ownership still running a flathead with 6 volts and everytime spring comes around the wing nut gets spun loose and a gulp of gas is dumped down. Yes if slightly too much the accelerator needs to be held down but also keeps the engine running longer as well and long enough to keep it running.
That was a VERY GOOD POINT brought up about in the event of an accident the fuel pump will keep pumping adding fuel to a possible fire or make things more hazardous!!
Now the check valves that Barry pointed out and yes they can cause problems!! My fuel pump is sitting on top of the intake manifold way above the fuel tank. Your 383 and 430 Mercury engines from the late 50's had them higher up as well. As Barry mentioned the check valves are on the inlet and outlet and not only do these valves get worn but the seals that seal them in the housing also shrink and can cause bypass. Of course your fuel can siphon back down to the level of your fuel in your tank creating a bit of an air lock. Yes the fuel pump can and will overcome this but it also slows down the filling process of your carburetor as well. Not only do they cause this but can also reduce the efficiency of your fuel pump.
Some people put a continously running electric fuel pump in series with the mechanical pump but be aware of the fact that if your fuel pump diaphragms leak or rupture, the electric fuel pump will fill your crankcase with gasoline. Some of the equipment I have worked on had the fuel above the transfer pump and if the transfer pump developed a leak you would find the crankcase filled with Diesel fuel.

Here is another solution instead of a questionable electric fuel pump, and that would be to start your car every month and let it run for a while to circulate oil around the engine and of course circulate fuel through the carburetor preventing the carburetor from becoming varnished!! When the fuel in the carburetor evaporates the float settles to the bottom of the float bowl. Also when fuel evaporates it creates varnish and where is your float again?? At the bottom with your float valve fully open and stuck from varnish. The total BS about Holley 4000 series being fire hazards is just that, total BS because ANY carburetor can have the float valve stick open and any carburetor can have the float spring a leak and fill up also causing the float to sink and cause the flooding!

[Egenolf]

Here are my thoughts to this problem:

1. for a long time, I had a transparent filter in the fuel line between carburetor and fuel pump. I have never seen that this filter ran empty.

2. I have installed a check valve in the fuel line between fuel pump and tank.

That?s why I do not think, gasoline will run back into the tank.

Nevertheless I have the same problems like you all: after two weeks, the engine starts very hard.

However, I do not think, that the whole gas evaporates from the carb but I think the flammable components evaporates from the carb.

The Holley has ventilation holes in the lid that promote the evaporation of the flammable components of the gasoline. That?s what you smell in your garage, Roger.

By the way: I would be happy if we could return to a neat tone here.

[Roger Zimmermann]

The Holley has ventilation holes in the lid that promote the evaporation of the flammable components of the gasoline. That's what you smell in your garage, Roger.

Absolutely, Holger! Another test, after one week, would be: taking the air cleaner assembly away, block the choke open an manipulate the throttle. If some gasoline (or whatever is coming out) is squirting out from the accelerator pump, the carb is not empty, but the remain liquid cannot burn.
The problem: the air cleaner from a '56 Eldo is damn heavy and I hate to remove it.

[Barry Wolk]

Why would they promote evaporation? Why does the float chamber ever need to be open to atmosphere?

[Mark Norris]

Why would they promote evaporation? Why does the float chamber ever need to be open to atmosphere?

I think Holger really meant "they allow evaporation" ..but as we know with a fresh gasoline vapor pressure of circa 7 psi it would be very difficult to stop it. I wish my German was as good as Holger's English.

All float bowls normally have to be maintained at atmospheric pressure so the jets work in a predictable way. The fuel rate through the jet depends on the depression in the carb air stream verses the atmospheric air pressure above the fuel level in the float bowl. For a carb to work in a predictable way some thing must stay constant eg. the height of the fuel level above the jet, the pressure above the fuel level (atmosphere), the ID of the jet and only one thing that varies with throttle change (ie. the depression in the air stream below the jet).

Many carbs are "fixed jet" like Holley, Carter, Weber, Dellorto etc.

A few are variable jet like SU ..actually I can't think of another.

Regardless they all rely on a fixed height of fuel with atmospheric pressure above.

[Barry Wolk]

This car has no choke at all. Scott says the only time it's even close to starting this fast is on a hot restart.

Two seconds of spray was sufficient to start this car easily. By the time the engine is out of fuel from the spray it easily restarts off the fuel pump.

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[Barry Wolk]

When I took the fuel line off the '57 fuel pump I slowly loosened the fitting and heard the distinct sound of liquid reacting to a suction. I cannot say how much of tube was emptied, but I believe that that confirms that a leaking check valve in the fuel pump will allow the fuel in the standpipe to be sucked back to the tank, at least to the level of the fuel in the tank.