Fuel pump

[rhschnauss]

I would like to mount an electric fuel pump to prime the carburetor before starting the car. Who has successfully done this and where did you mount the pump? The facet pump I bought is a pass through type and I will only be energizing to prime the system.

[Barry Wolk]

Fix your fuel pump check valves and you won't have to alter your car unnecessarily. A fuel pump is just a bandaid fix and it can kill you in a crash if its on, for any reason. If you're going to do it anyway, ay least use a momentary contact switch.

[Milsteads Garage]

Any electric fuel pump requires being mounted near the tank to work correctly. I planned on doing this but found it easier and about the same cost effectiveness just to buy a rebuilt fuel pump from Arizona vintage parts and install it instead. I completely agree that an electric fuel pump will help a 430 or 462 in a later car but on a 368 it isn’t really needed.

[Mark Norris]

My car is fitted with an auxiliary electric fuel pump located on the left hand main frame just above the rear axle so placing it close to the gas tank. The switch is located under the dash on the same panel as the antenna and interior light selector switch. Its an addition many MkII owners have made and its got me home on at least one occasion.

It helps in two ways a) if your car is only occasionally driven (like most of them) then it helps prime the fuel suction line to the engine mounted mechanical fuel pump, and b) it's a backup in case of valve failure of the mech. fuel pump. Its no surprise that modern cars are not fitted with an engine mounted fuel pump ..its a foolish idea to risk compromising the engine oil in the case of a pump diaphragm failure and its a poor engineering solution to attempt to suck a volatile fluid a long distance under negative pressure (far better to push under positive pressure).

Yes you could make the switch momentary for crash reasons but there were millions of cars manufactured with a non-momentary power supplies to the fuel pump (ie. supply connected to a ignition on circuit). If momentary it would also be something of a hassle to hold on if using the electric pump for backup.

[rhschnauss]

I use my mark II rarely and am tired of running the battery down and Having to recharge it just to get the car started. My 61 imperial has a rattle electric pump that I energize for 30 seconds and it starts almost instantly. Obviously the rattle pump primes the system and makes it easy to start after sitting for a while. That is my intention with installing one on the mark ii.

[Roger Zimmermann]

When my Cadillacs from the fifties are not started for about a week, the carb is empty, fuel evaporated. Thanks to an electric fuel pump in serie, the starting process for my '56 Biarritz is reasonable. With the Brougham, I had to do some manipulation to let run the original electrical fuel pump (located in the tank) to fill up the carbs, allowing the engine to start.
When I still had my '56 de Ville, I unscrewed a side bolt to fill up some gas into the carb.
Evaporation is not a myth, it's reality.

[Barry Wolk]

Roger, if the float lowers from evaporation, does the fill valve not open? If the fill valve opens and the check valve in the pump is defective,will the fuel not seek its own level to match that of the tank? Would a working check valve not keep fuel in the fill pipe?

[Barry Wolk]

There's another check valve that people forget about. The accelerator pump has to overcome a spring-loaded check ball at the bottom to squirt fuel on start-up. The check valve can stand open from debris. Mine did that. Fuel just dripped into the manifold until the bowl level dropped and opened the float valve, opening the system to atmosphere and drained the pipe because of the bad check valve in the fuel pump. Yes, evaporation is real, but there can be alternative explanations for an empty fuel bowl.

[Barry Wolk]

https://markiiforum.com/pictures/HolleySup.pdf

[Roger Zimmermann]

Roger, if the float lowers from evaporation, does the fill valve not open? If the fill valve opens and the check valve in the pump is defective, will the fuel not seek its own level to match that of the tank? Would a working check valve not keep fuel in the fill pipe?
To be honest, I never opened the fuel pipes to see if there is still fuel or not. Anyway, on the Carter WCFB carbs, the inlet fuel is above the fuel level; I suppose all carbs are the same. With the float needle open your theory is that this opening is allowing the fuel to go back to the tank, unless the corresponding valve located in the fuel pump is blocking that back flow. However, I don't share this opinion because the float needle is not designed for that.
A splendid example is the 57-58 Brougham models with the immerged fuel pump into the tank. There is no mechanical fuel pump, therefore no intake/outlet valves near the engine. But those damn carbs are empty after a week! Remember that gasoline now is way more volatile than in the fifties or sixties; this is most probably one of the aspect which cannot be put aside...The fuel vapors can escape from the vent valve integrated into the carb. When I'm taking one of my older cars at home, they are stored into a one car garage. The next day, there is a strong gasoline smell. However, if I'm attempting to start the engine from one of those cars the next day, no problem, they start immediately.; there was not enough time for the fuel to totally evaporate.
All my old cars have/had carter carbs. I don't know if a car with a Rochester carb would act identically.
A leaking check valve from the accelerator pump can also be noticed with an hesitant acceleration.
Of course, I cannot do anything on the Brougham now as I sold it last November.
This is the reflect of what I observed during the years I owned the cars; I cannot pretend that it's the sole explanation.

[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.


https://www.facebook.com/1055475400/videos/pcb.10223951069458676/958146101505652

[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.