The Stovebolt Site Forums The Shop Area The Electrical Bay Ignition cutting out

Got a weird situation going on and I need some input from ya'll. '50 3100, 6 volt system, all new wiring, new VR, new coil, new points/condenser. The truck had been running well with no issues of an electrical nature. Now, it has developed this issue: whether at idle or at higher RPM, the ignition will drop out momentarily, like it just skips a beat, then pick back up. I can tell it is electrical because the fuel gauge will drop and then recover every time the engine stumbles. I thought it might be the coil, so it has been replaced--no change. Then I replaced the condenser with no change. Battery voltage is right up there, all grounds have been checked, generator is putting out good voltage. I'm at my wits end as to what this may be.

The gas gauge does not depend on the engine running or missing. It is direct wired from the ignition switch. So seems like a ignition switch issue. It is cutting off power intermittently to gauge and coil. Gas gauge and coil are on the same ignition switch terminal per wiring diagram. Check wires at that terminal. If wires and terminals are tight, then probably the switch is acting up. If there is an unused terminal, try using that one for those wires. if you have the original switch, it has three terminals. Does not matter which terminal is used for what. They are all off or all on. Just so the terminal used from the ammeter has no other wire on it.
It could also be a similar ignition switch/wiring issue. Switch losing power from the Ammeter. (basically direct battery power)

More can be learned if we know what else goes off besides the motor and the gas gauge. I.E. lights, what the ammeter does, any other electrical gauges, radio, heater blower......


EDIT: if we find out everything is going dead momentarily, we will list more areas to check including the battery and it's grounds.

I was so focused on watching the gas gauge that I did not think to turn the lights on to see if they were affected. Tomorrow I will fire up and see what the lights and ammeter do; there is no radio or heater. I had considered the ignition switch, since it is original to the truck. Will check that out tomorrow.

Headlights might be a miner's canary for you here. They are not wired through your ignition switch so if the switch is intermittently cutting power off to your coil, etc your headlights won't show any flicker when that happens. Good luck!

A generator will keep the system running even if the battery is disconnected for a second
So it likely isn’t a battery issue nor a headlight circuit issue
Assuming the generator is working
So the problem is most likely where Bartamos suggested
Between key switch and coil
-a

If the headlights get dim while the misfire is going on, you probably have a loose wire coming off of the ammeter.
That happened to me once. Some dill weed mechanic didn't tighten the nut on the ammeter. I would have fired him on the spot, but since I am a one man operation, I had no one to fire...

Look for bare wires in places where they go through sheet metal panels. An intermittent short can cause the lights to flicker, and interrupt the ignition circuit at the same time.
Jerry

Well folks, I think we found the gremlin (not the one from AMC) that was causing the problem. Bartamos nailed it from the get-go. I went under the dash and swapped the wires from the I terminal over to the A terminal on the ignition switch and she has not missed a lick since. Cranks better, runs smoother. I just assumed that since the switch had been good for 73 years, it ought to still be good. Rest assured, there will be a new one under the dash ASAP. Thanks to all who responded and woke me up to the potential weak spot in the chain.

The lugs on the ignition switch are held on by rivets. They get loose of time.

Another dive under the dash and replaced the 73 year-old ignition switch and cylinder. Just not taking any chances on using that old piece of equipment. Now on to trying to find out why the VR will not let the genny do its thing.