Starter Post Voltages

[Guest Anonymous]

This isn't about my Z but it is about my Z hauler. A 71 chevrolet pickup with a 3 wire starter, I know I should have full battery voltage at the battery cable post on the starter, but the post with a "S" on it should have 12 volts also is that correct, BUT what about the other post "R" and what is the point of it and when should voltage be present and how much.

[Mike C]

The third terminal was used for points ignitions. It should have full battery voltage only when the ignition switch is in the crank position. The post was connected to the positive terminal on the coil. This provided extra voltage during cranking so the voltage lost through the ballast would not be too high, and allowed the engine to start easier. For the most part, it is not neccessarry, especially if you are running electronic ignition. I ran points distributors for years without the extra wire, but that's what it was there for. Running 12v to the points all of the time will cook them in very few miles.

[Guest Phil1934]

For point ignitions it supplies a full 12V to the distributor for cranking. Then the power goes through the resistor wire which drops it to 6V to not burn up points.

[Guest Anonymous]

So my main problem is excessive voltage drop in the ignition wire "S" post. I just checked again and now it only shows 8 volts, which I'am guessing isn't enough to create a magnetic field strong enough to pull the contacts together. Does that sound the most probable. The wires are in horride condition.

[Guest Phil1934]

Make sure you're in park and jump from the batt term to the ignition. A remote button is nice for this or you can hook a wire to the ignition post and touch it to the batt to see if that's it. If not it's the starter. Just don't get run over.

[Mike C]

The source of hot start problems in GM vehicles is a combination of the starter design that requires more current as it gets hot and the resistance in the ignition switch circuit (that is the idea behind the Ford solenoid, it is switched by the ignition switch which in turn sends full batt voltage to the starter, the ford solenoid is just a relay, actually.)First thing to do is make sure you have PERFECT connections on the battery, the starter, the battery to the block, and the ground straps from body and frame to engine. Then put your voltmeter on the battery (actually can do this first) and make sure it is fully charged at 12.6 volts. Then turn the key to the start position with the wire disconnected from the starter and measure voltage. Should be 10+ volts. This should start your truck. If this doesnot work, you can bypass the ignition switch with a pushbutton. Make sure truck is out of gear (or in park) and the parking brake is set, then connect one side of a push button to the big terminal on the solenoid and the other to the S terminal. This will let you know if the ignition switch is at fault. Also check to make sure that the truck is in park if an auto because of the neutural safety switch.

[Guest Anonymous]

Truck starts like a champ now, the problem was to much voltage drops in the pieced together ignition wire connections. And faulty ground when we were testing the starter.