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Been working to ready a restored 51 Chevy truck with a GMC 270 motor for first start. All 6V and wired as stock. Got fully charged battery hooked up and checked wiring. With key in OFF position, have 6+ volts at starter (connected directly to battery) and nothing at the coil. Put key in On position and get 6+ volts at positive side of coil. Push down on the starter switch mounted to the starter and nothing. Maybe the connections under this switch aren’t making contact? I can take it apart and check but would like to confirm that’s what the rest of you think I should do. Starter is 1107055 and completely rebuilt. I think I also read somewhere that new stators May have come with some type of melamine on them and if such wasn’t removed, it would keep the starter from turning over? Any help or thoughts would be appreciated!

Did you bench test the starter before installing it? If not, here's a quick test you can do without completely removing it. Use a big screwdriver or a pry bar, and just push the button on the starter switch- - - - -not the entire foot pedal linkage. If the starter itself is good, the motor will spin, but the drive gear will not engage the flywheel and spin the engine over. If that's the case, you've got a linkage problem, not an electrical one. I've seen people put the twist cap off a Coke bottle over the starter switch button as a temporary fix when the starter wouldn't turn due to sloppy linkage.

If the starter motor won't spin by pushing only the switch button, start looking for open circuits inside the starter, or possibly bad contacts in the switch itself. Places like NAPA and Rock Auto sell just the switch, not the whole starter, but a "rebuilt" unit should have come with a brand new, functional switch. Good luck!

Edit: Your picture shows a black label on the starter, which is correct for a 6V unit (12V has a red label) but the switch is for a 1955 or later model 12 volt starter. It will work OK, but the small red wire in the photo is not necessary for a 6V installation. It's there to bypass a ballast resistor for a 12V ignition system, and your 6V ignition does not use a ballast resistor. Wherever that wire is going, it doesn't need to be there on a 6V vehicle.
Jerry

Hey Jerry, I found one of my missing pairs of glasses. I believe that red wire is attached to the big nut on the starter switch (from the battery) and goes to the ammeter.

Hey Jerry, I found one of my missing pairs of glasses. I believe that red wire is attached to the big nut on the starter switch (from the battery) and goes to the ammeter.[/quote]


I tried to just push the starter switch down and nothing. And yes, that red wire goes to the ammeter. I rebuilt the starter with all new parts. Guess I’ll have to take the switch off and see what’s up.

OK- - - -you know what happens when we "assume" something! That wire hearing toward the front of the engine instead of the firewall fooled me! Also, try looking at the ground circuit- - - -all those billions of electrons the starter needs to make it run have to get back to the battery to complete the circuit. I've been tripped up by a layer of paint or some well-hidden corrosion on more than one occasion!
Jerry

Ok so I removed the starter. Bench tested. Could only get it to spin a little bit, kind of like in very slow motion. Wasn’t consistent and for sure was nothing close to what would be needed to start an engine. 6V system, but didn’t think the 12V switch would matter. Disassembled and took some pics. Would love to hear what folks think may be wrong.

How about a closeup of the inside of the switch (although you said it was new, and the contact button on the starter case looks clean), and one of the commutator. That would help find if there's an issue there.
Jerry's comment about making sure the ground path is good (no dirty high resistance connections) is appropriate. You need to identify anything either on hot or ground side of the circuit that would drip the voltage.
Also, be sure the battery has a good charge. A low battery would explain a slow starter.

Shine the commutator lightly (looks dull). Put it back together minus the foot switch. On the bench, get a GOOD ground on the starter metal. Touch the power post with voltage and see how it runs. Keep starter held down to avoid gyro spin/torque jump. Report.
It seems the lug on starter looks turned 90 deg?

Where's the other two field coils? There's supposed to be four of 'em! Those two pole shoes you removed are supposed to have coils around them, also! No wonder the thing won't crank!
Jerry

Maybe not 90 degreees, but definitely off kilter.
I was wondering about that. No need for shoes if they don't have coils around them.

Maybe the best option is to throw the parts in a box and take it to an old school rebuild shop and have them sort it out for you.

You rebuilt this starter? Check the brush system and your lug contact inside.

I do see many Delco starter rebuild kits with only two field coil windings. Some are for 12V conversion. Some for tractors. If you have installed a 12V conversion kit and running off of 6V. Could be a problem.

You need to take the warning from Kevin. The battery! Try a different battery.

Make sure the coil on the GMC motor is not wired for positive ground. But I guess the bench test eliminates that.

The starter will turn the same direction either polarity
It doesn’t have permanent magnets in it like tiny dc motors that can spin the opposite way when you flip the polarity
The starter windings and the armature both reverse when you flip polarity
1x1= 1
-1x-1=1
No rotation change
This is how your old AC/DC vacuum cleaners work too
Each AC cycle flips polarity but it still turns the same way
And then of course direct current will also work
-s

Battery was at 6.38V. Inside of switch is good, everything moves and contacts as it’s supposed to. Lug is crooked because I had to break the connections between it and the coils in order to get the commutator out. The starter only had two coils in it when I took it apart, does it need four? I’ll shine the commutator end up next time I’m in the shop. Does it matter if there’s rust on the pole shoes?

There are both 2 and 4 coil 6V examples on Ebay. The higher torque starters have the 4-coil setup. For the price, it wouldn't be a bad idea to install a 4-coil assembly. Rust on the pole shoes isn't a problem- - - -loose end bushings that allow the armature to drag on the pole shoes is.
Jerry

A battery can show "full" but break down immediately under load because of a bad cell or two. If you have not tried a different battery, you are not troubleshooting in a proper baseline approach. You also did not agree to try without the switch mounted. That would also be done with a different battery. You MUST start with the baseline being rock solid. Battery, battery connection and bare metal ground. To be 100% sure before tearing into other ideas. Don't trust batteries!!

You say the starter had only two coils, so we assume it was running good at one time and you didn't find it in an alley.

What are the brushes resting against in your pic?...and why?

So much shiny paint . How is the starter assembly going to ground with all that paint covering the mating surfaces.

I did not notice a ground strap were mine is by the starter ,but your gmc may be different?

Kevinski - my ground strap goes from the battery to the top of the transmission.

Dusty - I wondered the same thing. I took the paint off the end of the starter that contacts the bell housing and the face of the bell housing but obviously haven’t put back together and reinstalled yet. Should I also take the paint off the assembly faces of the different parts of the starter?

Bartamos - I can definitely test without the switch once I have it put back together, but I don’t have another 6V battery. Correct, it did start the motor previously with only two coils. The brushes are resting on a fiber washer that was on that end of the armature that just stuck there when I removed the armature.

Hotrod Lincoln - I’ll check again when I get it reassembled but don’t believe I had any contact with pole shoes.

The only really effective way to check the battery is to monitor the voltage at the posts (not the cable connectors) while the engine is cranking. A good 6 volt should show a minimum of 4.5-5 volts with the starter running under load, and the voltage should stay there for 20-30 seconds of continuous cranking. Spin the engine with the ignition disabled to use the starter as a battery load device. Even an almost dead, or defective battery will show 6 volts without a load on it.
Jerry

He can't spin the engine. He said the thing won't move on or off the truck. Gotta find some place that can load test the battery. That is the next thing to tackle. 100%

I'm pretty sure that as soon as the starter switch is pushed, the battery voltage will go to zero, or close to it, even if the engine won't turn. Doing a cranking test with the headlights on is another substitute for real test equipment. If the lights dim badly or go out altogether, the battery is discharged or dead. A quick bench test of the starter clamped in a vise with a 12V battery and jumper cables will tell if it's capable of cranking the engine, also.
Jerry

I agree with all that for sure. If it was me, I would not mess with the starter anymore until I had the battery tested or replaced. Otherwise, in my mind, I would still not know if it was the battery or the starter. Especially if the battery didn't go to zero and the starter wouldn't crank. Never hurts to buy a battery if your battery is more than 3-4 years old or use it's proration. I am making an assumption that he rebuilt the starter and has thought of all the possibilities. May be the foot button switch, but probably not. I am strongly suspecting the battery BUT I will say it must be deader than dead if it won't even move the starter on the bench or spark when bench cable is touched to it.... or growl. But we are not there to be able to judge.
So I hope the rebuild was wired properly and something not backwards or forgotten. A 100% good battery will prove that the starter is screwed up.
As long as battery cables are GOOD/NEW and their clamp ID's are CLEAN and the battery posts are CLEAN and he is touching an unpainted part when testing.

It would be possible to bench test the starter with a 12V battery also. That would at least prove if it will turn.

Thx for continuing to spitball on this all. I can for sure put 12V to it, I was worried that might damage the starter. When I said I didn’t have another battery, I meant I didn’t have another 6V battery...my bad. Should I reassemble and hit it with 12V?

I am nearly convinced it’s the paint/ground. Can anyone tell me, where do I need to ensure I have metal to metal contact? Between the housing and the pole shoes via the mounting screws? Between the housing and the nose? Between the housing and the brush plate? Cuz I don’t have metal to metal contact on any of these.

Strip the ends of the housing and both end plates where they touch each other, down to bare metal. NEVER paint components before assembly- - - -it's just cosmetics and a quick spritz with a rattle can after everything is bolted together is all you need. No wonder it won't work- - - -you've insulated all the parts from each other. The total resistance in a good starter circuit is less than 1/10 Ohm- - - - -almost a dead short.
Jerry

Come on bartamos, you’ve been too good to me to fold. Besides, a person has to learn somehow!

Will do Jerry, thank you!

One other related question...I’ve probably got the same problem with the generator, I assume I’ll need to strip it similarly? Or is this not a concern as long as it’s got good connections for the Armature and Field?

Yes, I'd suggest bare metal to metal contact between the generator housing and the end plates, and a dedicated ground wire connecting the generator housing to the regulator base. The generator uses the engine block and the end plates as a ground to complete the circuit back to the negative post of the battery, so there needs to be a very good ground circuit connecting the battery, engine, frame, body, and bed together. I use at least a #1 gauge welder cable as a ground, directly from the battery negative post to a BARE spot on the engine block or bell housing close to the starter, and smaller ground straps connecting the engine to the frame and body. That's been working well for me since the mid-1950's.
Jerry

Awesome Jerry, thanks again. Sorry for these silly questions, for some reason, these electrical things have alluded me 😩

I felt the same way- - - -back in the early 1960's when I started going to General Motors training seminars on automotive electricity. Then I ended up teaching it for close to 40 years!
Jerry

Finally got back out to work on the truck and, surprise, the starter runs great now! It was all the paint! I was beginning to doubt my own rebuild skills there for a bit... . Thanks again all!

Thanks for the update.

So leave in suspense!! Did the 270 Fire up??