Fuel pump discharging battery problem?

[FRED ZWICKER #23106]

I may have a problem with the electric fuel pump on my 1939 LaSalle convertible coupe. Car was purchased 2 months ago. Last Friday I ran out of gas (gauge was off, so now I know). I added 2 gallons to get to the gas station and filled the tank. I drove home (14 miles) without a problem. Car sat all weekend. This morning, was driving the car to work and noticed that the ammeter gauge was far to the left (discharging) while driving at highway speeds, even though lights were off. I drove back home and checked it futher. Here is what I found:

Key off - ammeter sits in middle. Turn on parking lights with key off - ammeter shows only a slight discharge. Turn on head lights with key off - ammeter almost full discharge (far left on gauge). Both of these instances seem normal to me. Then I turned off lights and turned on key but did not start car - ammeter shows full discharge (far left) and electric fuel pump is running and KEEPS RUNNING. With key still in on position, but motor not yet started, I then turned the electric fuel pump OFF - the ammeter goes back towards the center, but not quite to center, showing a slight discharge, which seems normal to me.

What I do not understand is that prior to all of this I am almost certain that the electric fuel pump cycled on for only a few seconds and then shut off (however I did not take notice of the ammeter at that time). It now seems as if the electric fuel pump will not shut off and battery discharges and even when running, shows a full discharge on the ammeter. I am afraid to drive the car, although this morning drove part way to work (about 4 miles round trip and no problem, other than the ammeter showing a discharge the entire trip and lights were off. I did not observe any fuel leakage and car ran well.

Is it possible that running out of gas previously could have damaged the fuel pump? Shouldnt the fuel pump shut off after it fills up the carburetor? I do not know what type of electric fuel pump I have, but do know that it is round and mounted verticlaly about half-way between gas tank and motor and has an in-line fuel filter between tank and pump and it looks to be fairly new. (I will try to take a better look in the morning). The fuel line runs from the electric fuel pump up to the original fuel factory pump, which may or may not be operable, but gives the motor an original look.

About 3 weeks ago, I installed an 8-volt battery and had the voltage set to about 9.  Had no problems during the past 3 weeks, so do not feel this could be the cause, but I am not sure.

Any ideas?

Fred Zwicker

[Geoff Newcombe #4719]

Someone more knowledgeable than I will no doubt give a more definitive answer to your question but it sounds to me as though your fuel pump may have finally succumed to the 9 or so volts it has had to eat when designed for 6 volts.  Your light bulbs will survive for awhile too but will burn out faster than usual.  Others may point out also that one of the keys to a good working 6 volt system is to make sure all of your ground points are clean, tight, and indeed are making a good ground.