I’m working on a model T that has been resting for over a decade, and I’ve run into an issue regarding the starter motor. At first, it seemed that nothing was happening after pressing the starter switch. Then I checked the voltage on the starter motor while pressing the starter switch and it remained zero. Then I disconnected the wire from the starter motor and looked at the voltage again. This time, after pressing the starter switch, I correctly measured the battery voltage (somewhat over 6 Volts).
I decided to measure the resistance of the starter switch and it was about 350 Ohms while pressed. As this probably needs to near to nothing, I decided to bypass the switch with a rather beefy starter cable and try it once more.
This time the starter motor was almost able to make a full rotation, but you could tell it was having a very hard time doing so. At that point the plastic of the starter cable started to melt and I decided to stop. The battery I’m using is rated 6V, 140Ah.
By the way, I’m able to rotate the engine using the crank by hand. But that also requires some strength. With my lack of experience I don’t know what is considered “normal”.
Should the starter motor be able to perform a couple of rotations effortlessly? And what amount of current is acceptable for this system? As it is now, it feels that if I would replace the starter switch it would burn out again immediately.
Yes the starter should be able to rotate the engine well. Since the engine has not run in some time are you sure the cylinder walls are OK? Try removing all the spark plugs and squirt oil down each cylinder. Then try it again.
BTW the high resistance of the starter switch is kinda expected. You need to disassemble it and clean it until you can see shiny copper and shiny steel. Then it will be near zero.
One more thing came to mind. The cable from the battery to the starter switch, and from the starter switch to the starter, should be 00 gauge wire wrapped in cloth. If you have 2 gauge wire wrapped in vinyl that won’t work with 6 volts.
Thank you very much for your quick reply, much appreciated.
I already tried to remove the spark plugs but they are stuck and was afraid I would damage them. But I’ll try it again and then lubricate the cylinder walls.
I managed to remove the sprak plugs. I found that it is relatively easy to rotate the engine using the crank with the plugs removed. As soon as I put the plugs back in, rotating the engine becomes a lot more difficult. But I guess that is a good thing, right?
Next up is revising the starter switch. My guess is that the starter motor will be able to rotate the engine if the spark plugs are removed. But with the plugs installed I think it will be the same as before, even after lubricating everything. I’ll post my findings later.
The reproduction switches are garbage. The key is restoring an original switch.
Thanks for your advise. I found that the car is already equipped with a reproduction switch. Fortunately I found the original switch in a box that came with the car, so I’ll attempt to restore that one.
I’ve opened both switches. The one in the car (the reproduction) looks like this:
The original one (I think) looks like this:
As a quick test I replaced the switch with a big bolt. I then let the starter motor spin with the spark plugs removed to see what it would do without any compression. I have posted a video of that here.
Then I refitted the spark plugs (hand tight) and gave it another spin. I have posted a video of that here.
I’m going to take the starter motor out and have it serviced by a professional. In the mean time I’ll restore the original switch and make sure the wires have the correct diameter. I’ll probably also run an extra wire from the starter motor housing to the battery to make sure it is grounded properly.
Your starter sounds fine. The reproduction switches use brass plated steel contacts so they work once then they are done like yours is. Originals are made better and yours looks fine. Frankly don’t bother with more grounds that is completely unnecessary.