VCCA Home Forums TECHNICAL - GENERAL Trucks and Vans 1946 pickup 6 volt starter problem

Here's a problem that must be pretty common I would think. I am not sure, but suspect either bad ground or a short in the system, but wanted to explain it to see what some of you think.

Really low power when starting, not enough to barely turn the engine over...I measured 6.11 volts on the battery.

I would be cleaning all battery connections (both battery terminals, connection at starter switch and where the earth connects to engine). If that makes little difference pull the starter and give it a good clean and lube. I would also have the biggest battery you can fit in the space.
Tony

Connections are very clean.

My batteries when fully charged have 6.4 volts. 6.1 is about 80% charged. Minimum CCA is 600 for me. Prefer as much as I can get short of an optima.

Alan,

Over the years we have all learned the hard way that you need pretty good size battery cables to make a 6 volt starter work well regardless of battery size and condition. My best guess is that your battery charger added enough capacity to make things work.

I like your idea to look for shorts and grounding problems. Unfortunately the capacity deficiency will not show up with continuity testing with an ohm meter.

One test you might consider is to bypass the disconnect. If it was designed for a 12 volt system it might not have the amperage capacity you need.

I would charge the battery at a slow charge at least overnight or perhaps 24hours. If it has had little use in the last year even though not old the plates can sulfate and reduce performance. After charging check it for specific gravity. Fully charged should be 1.275-1.300.

I was looking at an Optima online last night.

Darn it Alan. I was at the Santa Clara Fairgrounds yesterday to test drive a 2019 Ranger. I forgot about you, or I would have tried to come over to meet you. Sometimes I have a one track mind and was just thinking about the test drive.
Do you know what size battery cable you have especially on the positive?
I just measured my 48 outside diameter and it is .061. I think it is a 01 or 00 size cable. I also measured my 46 and it is .041, I think that is really to small even tho it spins over and starts good.
Just remembered I have a cable in a box and just measured I and it is .050. It says it is a 1 gage. I know this is the outside diameter that can very depending on the thickness of the insulation.

Yeah, close by.

Currently the way the truck is wired is skeptical, IMO, but I haven't been able to trace everything yet.

Looking into it.

It does not make a difference whether the disconnect is on the positive or negative side. Replacing the cables with new 2/0 CRIMPED ones is a good idea.

Yes, I have disconnects on negative post of my flatbed and forklift.

still working on this...

In theory it should not matter which side of the battery the disconnect is on, so long as the circuit is opened. When I am disconnecting a battery I generally disconnect the "earth" 1st, that way if I happen to bump the spanner between the "live" and "earth" there is no circuit to cause sparks.
Tony

I agree.

The way I have seen all the early (prior1960) is the the battery negative terminal bolts to the engine close to the battery with a heavy cable and the body earth sometimes is a 2nd lighter wire that joins the main near the post or the engine cable connects to the body then to the battery. Either way should work fine when all connections are clean.
Tony

Got the crimper today.

Still running some tests...

It sounds to me like your starter doesnt have a ground. I guess thats the same conclusion you came to.

I don't know what the little post on the side of the starter switch is. I have never seen a post there, and I am relatively certain it is NOT supposed to be there, and therefore your truck should work fine without it.

It LOOKS like a starting bypass for the ignition. I have never seen one on a Chevrolet foot pedal starter. This is a device to increase ignition voltage during cranking, and is used only on 12 volt vehicles as far as I know. If it really were a starting bypass, something would have gone up in flames (probably that black wire) the first time you stepped on the starter because the terminal would have become hot, and the black wire, being much smaller that the battery cables, would have acted as a fuse. So, it isn't a starting bypass.

There is no reason for a small ground like that on a starter, and apparently that is what it is, just like you thought. It shouldn't be there. The fact that it needs to be there for the starter to work implies that it is acting as a negative battery cable, and all of the starter current is going through it. It is too small to act in that capacity, and if the starter were dragging for any reason, that little wire might get REALLY hot.

None of that matters because once the actual problem (whatever that might be) is solved, the wire and the little post will be completely unnecessary.

The starter should be grounded through the flange where it bolts to the engine/bellhousing/transmission. Paint can interfere. The flange should be clean where it mounts. I have yet to see one that wouldn't try at all because of paint, but it is possible.

An electrical circuit is a circle. Since there is only a mechanical switch and heavy cables, it is a really straightforward circuit.

The circuit goes from the positive post of the battery, through the switch, through the coils and armature of the starter, to the starter case, back through the bellhousing/engine/trans and from there either (1) through a huge ground strap or cable to the frame, through the frame, and from the frame through the negative cable,back to the battery. OR (2) through the bellhousing/engine/trans, and through the negative cable back to the battery.

Either will work, and I will have to leave it to others in this thread to tell us which is correct for a 46 truck. I suspect (2).

I gather your positive cable goes directly to the starter switch on top of the starter. What does your negative cable bolt to?

It sounds to me like that extra wire at the starter grounds the the dash panel/ignition switch. If the starter was not grounded it would not turn over when the foot switch is operated.

Yes, pretty much the theory I've been going on.

Hi Alan,

Sorry that I missed some very basic points somewhere in all this. Thanks for your patience in explaining the situation to us.

Where does the negative cable from the battery attach to the engine or transmission? If it is grounded to the frame that might be creating the problem unless there is another cable from the engine/transmission to the frame. My friend's '49 pickup started great until we installed new motor mounts! We figured out that the old mounts were so bad that they allowed the engine to settle on the metal sleeves in the mounts and that grounded the powertrain. He had connected the ground to the frame not realizing there was a mounting boss for it on the engine.

Is the disconnect switch out of the circuit now? If it is a switch designed for use on a 12 volt system is might not have enough capacity for the 6 volt starter amperage.

Remove the distributor cap and with the ignition switch turned on manually open the points and check for spark both with the wire connected to the switch at the starter and with it disconnected. I am guessing that with the wire disconnected you will not have a spark (current) and your problem is in the ignition circuit.

No, thanks for yours.

I am trying to determine if the small wire at the starter is the power supply to the ignition circuit. You can check as I posted above or simply use a jumper wire and touch it from the terminal on the switch to ground momentarily. If it sparks it's a power feed for ???? in the ignition circuit. The wire most likely goes to the ammeter which would feed the ignition switch. Rather than try to explain the whole process it would help me more if I knew where the wire in question goes to .