I have a question about my 1946 Ford Delux coupe. V8 Engine is rebuilt, it has the 6 volt positive ground system, stock crab distributor and can style coil. It is hard to start, sometimes very hard. But when I ran a "hot wire" from battery to coil, turned on ignition switch, pushed the starter button, it started in about two revolutions. The engine then runs fine after removing the hot wire. My thought is to use a 6V relay and wire it so that when the starter button is wired thru the relay so that while starting, the full 6 volts go to the coil. when the engine starts, current goes thru the resistor. Question #1: is this feasible? Question #2: would it be better to replace the 3-pole solenoid with a 4-pole and wire it like the '50s Fords? (I'm assuming the Ford tractor 6V 4-pole solenoid has the same function where that 4th pole will send full 6 volts to the coil only when cranking? True/False?)
That should work fine. On the sbc's that were 12v and most other GM cars beginning in the 50's, all had a separate "R" terminal on the solenoid that sent the full 12v to the coil directly, bypassing the resistor when starting.
I’m one of those people that thinks if it worked in ‘47 it should work now. Have you got a multimeter so you can check: Resistance of the resistor Voltage at the coil points open (about 6v) Voltage at the coil points closed (about 4v) Also do you know you’ve got the correct coil?
Many can style coils have internal resistors. If your wiring is stock, the ignition switch wire runs to a circuit breaker under the dash which includes a resistor. There may be a possibility you may be dealing with too much resistance. Take a look at your coil and see if there are any markings stating whether or not it has internal resistance.
I don't have enough experience on 46 Fords to confirm any of the fine folks who have already posted, so I'll just repeat something that applies to ALL 6 Volts systems. Clean every contact in the circuit and all battery cable connections! Resistance in these can and will cause annoying electrical issues.
First thing I'd check is the coil primary resistance. The general rule of thumb is you want 1.5 ohms in a 6 volt points system and 3 ohms in a 12V system. The 12V system can be either a coil with a 3 ohm primary or a 1.5 ohm primary ran in series through a 1.5 ohm resistor for a circuit total of 3 ohms, with the latter being typical. This is to limit current and prevent overheating the coil at slower speeds as well as preventing burning the points. If the existing coil has a primary resistance under 1.5 ohm by 25% or more, then a resistor would be needed. But cleaning all connections in a 6V system should be on the 'to do' list in any case... Don't forget the grounds, pay extra attention to the ground path from the distributor case to the battery ground. This should be as close to zero ohms as you can make it.
@24bolt , I'm running an 8ba with a stock '51 6 volt coil in my '40 Ford. I bypassed the resistor under the dash because I had the same problem as you. The original '40-'48 coil needed that resistor, '49 and later did not. Simply move one of the resistor wires onto the same post as the other wire. Job done. Dave
If you are using a modern coil, get rid of the stock resistor. You don't need it. If you are running the old stock coil that came with the crab distributor you should keep the resistor. Those were made to work with it on the 6 volt system. If using a modern coil on a 12 volt conversion, use the correct resistor for the coil and get rid of the old one under the dash. Sorry to repeat what others have said but that's how it works.
Thanks for all the replies. The previous owner had tried running redundant ground straps, going to an 8-volt battery and had another coil in the trunk. So he had tried to fix problem with hard starting. The coils look the same as I'm used to seeing on a pre-HEI chevy, no resistor. One improvement I made to how it runs was to wire the coil correctly. The positive ground system now has the positive post on the coil wired to the distributor. If I can eliminate the resistor under the dash, that seems too easy, but great news. I'm sticking with using a 6-volt commercial battery because the car has 6-volt electric fan, wipers and fuel pump. I'll check for the 1.5 ohms. and I agree, if it worked in 1946, it should work now (with slight improvement).
My previous post is probably confusing. That's what happens when I stay awake too long so I'll try again. The reason Ford used the resistor was to lengthen the life of the points. It lowered the voltage at the distributor to about 3 volts and used dual points to give the coil more saturation time before firing the plugs. It worked really well with the original coil but not with a modern coil. Modern coils are made to use 6 volts with the full 6 volts. No resistor needed. Don't use one. That would put you right back where you started. Easiest way to get rid of the old resistor is to just connect both wires to one post. So, resistor for 12 volts, no resistor for 6 volts. You are right, the reason it had an 8 volt battery was probably trying to cure the problem you are having. Follow these instructions and let us know how it works.
Biggest problem with using an 8 volt battery as a bandaid for poor grounds and/or too small of cables and wires is a 6 volt system puts out 7.5-8 volts at best unless the regulator has been messed with and adjusted to 9-10 volts to keep the 8 volt battery charged properly. Has to do with specific gravity and all the technical stuff! So in reality, the 8 volt battery ends up being under charged and really no better than a proper 6 volt battery and system. Not to mention 6 volt bulbs burning out prematurely if the voltage reg IS cranked up. Dave
Assuming the lamps aren't saved by the same voltage drop problem that caused someone to try the band aid battery in the first place. Still, the proper fix is to get the original system design to work as it should again, or possibly a full 12V conversion as those are less prone to voltage drop issues and it's easier to find replacement lamps, batteries, ignition coils etc.
Thanks Dave, the 8-volt was a bandaid attempt. There was a new looking regulator that WAS messed with in the batch of parts . But he went back to an older one. I replaced the 8-volt with a 6-volt commercial NAPA battery with a much higher CCA rating. Haven't yet got out there to try Glenn's fix, but I don't doubt it will work. Whoever did the amateur restoration (previous-previous owner) installed complete new wiring harness, so connections are good. Just need to figure out what a few loose ends are for.
Are you saying that if I disconnect both primary leads to the coil, the resistance within the 6-volt coil should be 1.5 ohms?
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