1931 Stalls when any load is put on battery

J

jamesivta

Junior Member
I have a 1931 79B delivery. It had sat for about 5 years. I have rebuilt the carb. Cleaned all the fuel lines, put in a new battery and reset the timing. The car starts instantly. Runs great, with a good idle. It was converted to 12 volt some time in the past. The only issue is when I put any load on the battery, the rpm's drop to almost nothing and it stalls a lot of the time. I just warmed up the vehicle. I sat in the driveway with it idling perfectly, pushed in the brakes and it died, same thing happened when I turned on the headlights. I did this with the car sitting still and not in gear. I did notice when I hit the brakes or turn on the lights, the ampmeter shows a pretty big initial draw. Any thoughts on what might be causing this.
 
Take the battery out and have it load tested at an automotive parts store. Before or after that, measure the voltage at the starter switch when the lights are turned on. It could also be that your generator/alternator is not putting out. Measure the voltage at the starter switch when the engine is at a fast idle, 1,200 rpm. It should measure about 14.4 volts. If the battery checks out and you still have a problem, clean and tighten all electrical connections, including at the battery posts and the ground strap for the battery. If you do not have one, add a second battery strap that hooks to one of the bolts on the transmission.
 
Assuming you have a positive ground system, run a temporary wire from one side of your key switch to the starter cable post or the (-) post on your battery. Run a second wire from the other side of the key switch to the (-) post on the coil. If you have any other wires connected to the key switch remove them. If your distributor is electrically okay you should be able to run your engine without stalling. If this eliminates the stalling problem you have a problem somewhere in your in wiring that is unrelated to the ignition system.
 
Remove the battery ground cable from the frame and clean all the paint, rust and crud off the raised boss on the frame until it is bright shiny metal. Wire wheel the end of the cable that connects to the frame. This is the most overlooked electrical connection on a Model A.

Tom Endy
 
I will second what Tom Endy said above. I did exactly what he mentioned in my 31 roadster and still can't believe the issues it mitigated. Be sure to tighten the connections too - that may have been part of the issue, but certainly not the entire issue. Good luck!
 
Once the engine has been started it will continue to run even if the input voltage from the battery to the coil is as low as 1.5volts. This assumes there are no other accessories in the circuit. My post #4 is intended to verify that your ignition system is working correctly. All the posts recommending cleaning the battery connections and making sure the engine is properly grounded to the battery are super important. If you are using a battery disconnect switch that mounts on the battery post remove it and throw it away.
 
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