How our starters work

[VetteVet]

This may help a lot of you understand how the starter works and be able to trouble shoot them.


The starter cycle starts with the key switch turned to the ST position and power is routed via a 12 gauge purple wire to the neutral safety switch on automatics, and to a neutral or safety switch on the transmission, and some times on the later models, to a clutch switch. From there it goes through the firewall block to the S terminal on the starter solenoid.





The solenoid is an electromagnetic device that also acts a relay. The electromagnetic function pulls the starter bendix lever and throws out the starter gear to engage the flywheel.

At the same time the contact washer in the solenoid inside near the rear, moves to the rear and joins the two main terminals on the starter. The battery cable at the top and the starter field terminal at the bottom.
Note the red arrows.



This feeds battery power to the starter windings through the starter brushes and spins the starter armature turning the starter gear and the flywheel.

When the key is released the key switch goes to the ignition position and
releases power to the solenoid and a spring inside the solenoid returns it to the forward position breaking the contact on the two main terminals for the starter and the cycle stops.
shown below.

[Andy4639]

VetteVet you are just amazing man! Great write up. This needs to be put in the electrical stickeys!

[franken]

Nice but the large + cable doesn't go through the junction block as suggested in pic #1.

[70cst]

Great info

[luke1968c10]

My '68 with a 250 6 cyl starter will work good when the air temperature is warm but on a cold morning the starter just spins freely. If I keep bumping the key over and over it will eventually work. I can get it to work faster by holding the key in the start position with the starter spinning freely for about 10 seconds then when I let off the key and turn it again it will work. Does this sound like the solinoid? Thanks.

[C20ELEPHANT]

VetteVet, could you clarify a few a few things, haven't kept up on this these starters in years. What starter type is equipped on my 1982 as opposed to the one a friend told me to purchase, memory fades been installed for 5+ years now. I think it came off a about 1990's truck and is substantially smaller in body size and brings the solenoid further away from the heat of the header and a lot easier to install in the limited space....

[VetteVet]

Originally Posted by Andy4639

VetteVet you are just amazing man! Great write up. This needs to be put in the electrical stickeys!

Thanks Andy, a mod can do it.

Originally Posted by franken

Nice but the large + cable doesn't go through the junction block as suggested in pic #1.

Look again, The block is a junction block not the wiring block that we have on the 67 to 72 years. The big cable just bolts on there. It doesn't go through the firewall. This is an inclusive year thread and the schematic is meant to show the electrical path not the actual physical path of the wiring. The lower half of the picture shows how it goes on the earlier years like the 64 to 72 models.

Originally Posted by luke1968c10

My '68 with a 250 6 cyl starter will work good when the air temperature is warm but on a cold morning the starter just spins freely. If I keep bumping the key over and over it will eventually work. I can get it to work faster by holding the key in the start position with the starter spinning freely for about 10 seconds then when I let off the key and turn it again it will work. Does this sound like the solinoid? Thanks.

Luke, the piston or plunger shown in the 2nd and third pictures is connected to the starter gear arm and when the solenoid is energized it becomes an electromagnetic and it pulls the plunger rearward into the wiring coils of the solenoid and should shove the starter gear out into the flywheel gear.

The plunger is not directly connected to the solenoid but rather it floats inside the solenoid body. If the voltage is low on the battery or the S terminal the solenoid windings will not have enough magnetic power to pull the plunger far enough to engage the starter gear. Then we get the dreaded click, click, click, that we love to hear. In your case the relay in the solenoid will engage the contacts for the starter windings and cause the starter to spin without allowing the plunger to move the Bendix gear into the flywheel.

When it's warm outside or after you've spun the starter several times and warmed the solenoid, The plunger will move freely enough to engage and it then works. In short if you have a good clean connection on the starter S terminal and you're getting enough voltage to the solenoid, and it still won't engage then you will need to replace the solenoid.

The next time it happens you should try jumping from the large post on the solenoid to the S terminal and see if the engine turns. Use caution it may start and move the truck. If it still acts up then the solenoid is bad but if it works every time then the wiring to the S terminal needs attention. We have several threads on here to explain how to wire a remote solenoid, which will give you full power to the S terminal. Post in the electrical section if you are interested.

Originally Posted by C20ELEPHANT

VetteVet, could you clarify a few a few things, haven't kept up on this these starters in years. What starter type is equipped on my 1982 as opposed to the one a friend told me to purchase, memory fades been installed for 5+ years now. I think it came off a about 1990's truck and is substantially smaller in body size and brings the solenoid further away from the heat of the header and a lot easier to install in the limited space....

I'm not an expert on all the parts for all the model years but I believe the 82 still uses the same part no. starter as the older trucks. The one your friend told you about was probably a mini-starter which GM sells as well as the aftermarket. They are smaller in size and have more torque than the OEM starters. They are usually a cure for the dreaded heat soak problem associated with headers. I could research the stock starters for the later years and see if they decreased in size like yours or maybe a parts store would know offhand.

HTH VV

[C20ELEPHANT]

VetteVet, thanks for the info, writing it down cleared some cobwebs (more than cobwebs actually) and I believe I purchased it from AutoZone. I'll look through some receipts tonight, if I find the part number and post it for the rest of the guys having issues with heat soak especially the solenoid. The motor is a small block 350 not sure of the ring gear count...

Found it DL9990S

Posted here also...

http://67-72chevytrucks.com/vboard/s...d.php?t=286857

[Downtown]

Vettevet

Thanks for taking the time to do that. It is great to finally understand how it works.

[slikside]

Vet,

Thanks for the detailed write up.

I don't have any starter issues right now, but this one is going into the "personal library" for future reference.

Once again, very educational!

[C20ELEPHANT]

Originally Posted by C20ELEPHANT

VetteVet, thanks for the info, writing it down cleared some cobwebs (more than cobwebs actually) and I believe I purchased it from AutoZone. I'll look through some receipts tonight, if I find the part number and post it for the rest of the guys having issues with heat soak especially the solenoid. The motor is a small block 350 not sure of the ring gear count...

Found it DL9990S

Posted here also...

http://67-72chevytrucks.com/vboard/s...d.php?t=286857

More info on the starter PG260 ACDelco.

http://www.acdelcotechconnect.com/ht...tart_pg260.jsp


PG260 Starter

Light Duty V8 Gasoline Engines to 7.4 liters, Passenger Cars, Vans, Small Trucks, and Marine

ACDelco's Planetary Gear Drive (PG260) offers superior performance in a starter with exceptional durability. The PG260 is suitable for V8 gasoline engines of up to 7.4 liters for passenge cars, vans, trucks and marine applications.

The 4-pole, permanent magnet field consists of shunted Magnequench magnets mounted inside a zinc-chromated frame. No field coils are required. The armature is banded, impregnated and balanced for high performance and durability.

The armature drives the planetary gear set, which in turn is connected to a roller type overrunning drive.

The solenoid is sealed with an integral cover for maximum reliability with minimum weight, yet is still serviceable.

Four long-life brushes are used in radial brush holders with torsion springs. All brush rigging materials are corrosion resistant.


Figure A

Specifications:
System Voltage: 12 Volt
Rotation: Clockwise
Mounting: Flange or Pad Mount
Performance: 1.7 KW
Weight: 3.5 lbs.

Amazon
ACDelco 323-485 GM Original Equipment Starter Motor, Remanufactured

[R.L.]

Thanks for posting.

[RichardJ]

I'm not sure I like those drawings for the Delco Solenoid. I couldn't find a better drawing.

A Delco starter Solenoid has two windings. A Pull-in winding and a Hold-in winding.

The Pull-in winding is a high-current winding because it has to do the work of pulling the plunger and moving the lever and gear. The pull-in winding is connected to the "M" post and is grounded through the motor windings and brushes to ground, inside the motor.

The Hold-in winding is a low-current winding, because the work of pulling the plunger has already been done. The Hold-in winding is grounded to the body of the solenoid.

When the Hold-in winding is holding the large washer against the two contacts, the Pull-in winding is shorted out and no longer drawing any current.

[VetteVet]

Originally Posted by RichardJ

I'm not sure I like those drawings for the Delco Solenoid. I couldn't find a better drawing.

A Delco starter Solenoid has two windings. A Pull-in winding and a Hold-in winding.

The Pull-in winding is a high-current winding because it has to do the work of pulling the plunger and moving the lever and gear. The pull-in winding is connected to the "M" post and is grounded through the motor windings and brushes to ground, inside the motor.

The Hold-in winding is a low-current winding, because the work of pulling the plunger has already been done. The Hold-in winding is grounded to the body of the solenoid.

When the Hold-in winding is holding the large washer against the two contacts, the Pull-in winding is shorted out and no longer drawing any current.

Here you go Richard. These are rather simplistic but they do show the windings.

[RichardJ]

I like the last one on the bottom. Very clearly drawn and correct.

[luke1968c10]

I replaced the starter on my truck and it still spins freely the first time I hit the key. She second time I try it cranks the engine great but it makes a weird noise. I am getting full power to the S terminal and even tried jumping it over with a screwdriver. It engages almost always now except for the very first time you hit the key. Does it need to be shimmed? There were no shims in the starter I took off. Thanks for the help.

[Wrenchbender Ret]

When the starter spins but doesn't engage the engine, the most likely cause is a bad starter drive (sometimes called a Bendix). It is a one way clutch. When they get worn the gear just spins & doesn't turn the engine. If you have some mechanical expertise, you can replace it yourself & clean up the starter & replace the brushes if needed. This is better than some of the "rebuilt" starters you get now. Of coarse if you get it open & its all burned up inside it is time for a replacement.

George

[Accelo]

I had no idea of the pull in and stay-in windings of the coil. Great documentation.
What I didn't see mentioned it when you let go of the key the fork is retracted by the spring. The spring pushes on the fork actually acts as a brake. It stops the armature from spinning any longer than necessary. This keeps the brushes from wearing prematurely.
Cheers

[Keith Seymore]

[subscribing]