How many volts needed at a starter

[hounddogs!]

This is on the Buick (300-4V Skjylark), but same theory should apply.

I get a good strong click from the solenoid, then absolutely nothing as far as turning the starter motor over. I'm seeing some big voltage drops, but don't know if they are too much.

12.2V across the battery posts
11.0V at the back of the ignition switch
9.5V at the fuse block during crank
8.25V at the S post on the starter during crank

If I hear that 8+ should still turn the starter over, I'll open it up and clean the ring.

TIA
Loren

[VetteVet]

Try reading this thread and also the link I posted in post 21.

http://67-72chevytrucks.com/vboard/s...d.php?t=574411

[Blue72slab]

Good reading above. I use the updated charging system detailed on MadElectrical.com on my 72 C20 and 68 Camaro as well as the ford solenoid fix. Never a problem starting or EVER having to replace a starter.

[hounddogs!]

Thanks guys. If nothing else, I know that I lose 4V by the time I get from the battery to the start post on the starter. I have a 40A Bosch relay in hand to ensure something closer to battery voltage to the starter.

[VetteVet]

Originally Posted by hounddogs!

Thanks guys. If nothing else, I know that I lose 4V by the time I get from the battery to the start post on the starter. I have a 40A Bosch relay in hand to ensure something closer to battery voltage to the starter.

Try jumping from the large cable post on the solenoid to the solenoid S terminal. This eliminates the S terminal wire. If the solenoid is not connecting the starter cable with the fields, the starter won't turn but the solenoid may click. 8 volts at the S terminal is unacceptable. This test will put a full 12 volts on the solenoid. Be sure to disconnect the coil or the distributor so it wont start.


This what you are contemplating?




If you are losing 4 volts at the S terminal then you have a large resistance on the purple wire circuit and it's probably just a matter of time until you lose all your current in the purple wire.

[hounddogs!]

Originally Posted by VetteVet

Try jumping from the large cable post on the solenoid to the solenoid S terminal. This eliminates the S terminal wire. If the solenoid is not connecting the starter cable with the fields, the starter won't turn but the solenoid may click. 8 volts at the S terminal is unacceptable. This test will put a full 12 volts on the solenoid. Be sure to disconnect the coil or the distributor so it wont start. Done, starter operates correctly with S jumped to the heavy lug.


This what you are contemplating? Yep.

Attachment 1630412


If you are losing 4 volts at the S terminal then you have a large resistance on the purple wire circuit and it's probably just a matter of time until you lose all your current in the purple wire.

There's some loss in multiple segments (batt to ign, ign to fuse block, fuse block to S post). Factory wiring will be updated at some point. Until then, I prefer that the 8.x volts at the purple wire run a relay rather than running the starter solenoid. Thanks for checking back.

[VetteVet]

Originally Posted by hounddogs!

There's some loss in multiple segments (batt to ign, ign to fuse block, fuse block to S post). Factory wiring will be updated at some point. Until then, I prefer that the 8.x volts at the purple wire run a relay rather than running the starter solenoid. Thanks for checking back.

I didn't go through the troubleshooting process on the purple wire because I had a hunch you would want to use the relay. I think you might rethink that idea if you can solve the voltage drop on the S wire, since you won't have to add the wiring for the relay.

You recall that I suggested jumping the solenoid at the starter to take the S wire out of the equation, and determine that it was the cause of the starter failure. That would be helpful, but as you have already determined, it only has 8 volts on it at the solenoid, which isn't going to cut the mustard.

Question is Why? What you need to do is find out where in the S wire's path the voltage drop is at and repair it.

This is one of the simpler circuits in the truck harness and it is illustrated below. It starts at the key switch, with the first connection at the battery power red wire. You have to have 12 volts there. Then the next connection is inside the ignition switch between the red wire and the purple wire, when the switch is turned to start.

Now you are saying " I know all that so what?" But you don't know all that, because you said that the purple wire goes to the fuse panel, when in fact it doesn't. (no offense meant)

From the key switch it goes to the neutral start switch and from there it goes to the inside of the firewall block, and through the firewall block and on to the starter solenoid.

Now for the trouble shooting.
We can assume that you have 12 volts at the key switch if the truck runs and the headlights are bright and the wipers work etc.

Next we will pull the plug on the neutral start switch and check the voltage on the purple wire while holding the key to the start position. One side of the plug should have power and the other will be dead. If you get the 12 volts, then the connection inside the key switch is good.

Now we can check the NSS by jumping the NSS plug and try cranking the starter, or by checking voltage at the solenoid. If either the starter turns or the voltage goes up to 12 then the neutral start switch NSS is bad or the next connection is at the firewall block and there is a poor connection there.

Here is the path of the S wire.







and just for grins the NSS.




This troubleshooting is easy, and should point out the weak spot quickly.

[Moose Monkey]

Vette, just love reading your answers. Thanks again