Starter problem...

[1411506]

So...trying to start my car for the first time in a looooong time.
Got all the prep work done.
When I turn the key...nothing.
Checked that power was getting to the starter via the primary connection - OK
Checked power to the solenoid when the key was all the way turned....nothing.
Then checked the yellow wire at the 14 pole connector where the power first comes into the cdi box area - there is power there.
Checked the yellow wire as it comes into the second 14 pole connector - there is power there....but only if the connector is not connected????
When I connect the plug, I lose power to the yellow wire.
I can take the plastic cap off the top of the connector and hook the multi-meter directly the yellow wire coming out of the plug...no power. I can actually pull the wire out of the connector and put the multi-meter in the hole and get no power. This is the same hole I did get power from when the plug was not connected?
So, what could be causing this?
Thanks in advance for any help!
Rob

[911pcars]

I didn't see where you checked the ignition switch. The starter solenoid gets the yellow wire signal from terminal 50 on the switch in the cranking position.



Although not directly related, review the circuit diagram here that describes the ign. system. Mine's a '69, fairly close to yours.

http://members.rennlist.org/911pcars/RemoteStarter.htm

Hope this helps,
Sherwood

[1411506]

Hi Sherwood - in the cranking position, I do get power at the ignition switch, terminal 50.
I can still see power at the 1st 14 pole connector in the cdi box area. Then, following the yellow wire to the second pole connector - if the plug for the second pole connector is unplugged...I can see power at the yellow wire at the 2nd pole connector. If the 2nd pole connector plug is plugged in, then I no longer see power at the yellow wire....something happens when I plug in the plug into the 2nd pole connector.
Hope that makes sense.
Rob

Originally Posted by 911pcars

I didn't see where you checked the ignition switch. The starter solenoid gets the yellow wire signal from terminal 50 on the switch in the cranking position.



Although not directly related, review the circuit diagram here that describes the ign. system. Mine's a '69, fairly close to yours.

http://members.rennlist.org/911pcars/RemoteStarter.htm

Hope this helps,
Sherwood

[911pcars]

Rob,
Not sure about a '70, but the yellow wire from the ignition switch goes directly to the starter solenoid. In that there's another yellow wire in the engine compartment isn't necessary to energize the solenoid.

You can confirm the solenoid and starter operates by temporarily connecting a jumper wire from the battery cable at the starter to the #50 wire terminal on the solenoid. A remote starter switch makes this temp. connection less intimidating from 4' away. Don't forget to shift into neutral and chock a front tire.

Sherwood

[1411506]

Hi Sherwood - in the 70, the solenoid wire goes from the ignition switch to a connector near the cdi box - it then routes to a second connector - at this point it splits and goes to the starter and the temperature time switch.
I'll try to jump the solenoid directly from the battery to see what happens.
Rob

Originally Posted by 911pcars

Rob,
Not sure about a '70, but the yellow wire from the ignition switch goes directly to the starter solenoid. In that there's another yellow wire in the engine compartment isn't necessary to energize the solenoid.

You can confirm the solenoid and starter operates by temporarily connecting a jumper wire from the battery cable at the starter to the #50 wire terminal on the solenoid. A remote starter switch makes this temp. connection less intimidating from 4' away. Don't forget to shift into neutral and chock a front tire.

Sherwood

[1411506]

Starter is fine - I hooked a jumper cable to the pin on the second connector corresponding to the yellow wire and turned the key to the cranking position.

Originally Posted by 1411506

Hi Sherwood - in the 70, the solenoid wire goes from the ignition switch to a connector near the cdi box - it then routes to a second connector - at this point it splits and goes to the starter and the temperature time switch.
I'll try to jump the solenoid directly from the battery to see what happens.
Rob

[911pcars]

Originally Posted by 1411506

Starter is fine - I hooked a jumper cable to the pin on the second connector corresponding to the yellow wire and turned the key to the cranking position.

Rob,
Hmmmm. You shouldn't have to use the ignition switch. Connecting source voltage (via the battery terminal on the starter motor) to the solenoid #50 terminal should energize the solenoid by itself; no action needed at the ign. switch.

If the engine cranks with this temp. jumper connection and doesn't with your ignition switch, I'd suspect the switch (at least at the #50 crank position).

Sherwood

[rick-l]

So when you take the yellow wire off the starter and turn the key to start voltage is present? When you hook the yellow wire back up to the solenoid it is not?

Sounds like you have a voltage divider circuit where the resistance of the starter solenoid is the << less the the defect upstream.

[911pcars]

Originally Posted by rick-l

So when you take the yellow wire off the starter and turn the key to start voltage is present? When you hook the yellow wire back up to the solenoid it is not?

Sounds like you have a voltage divider circuit where the resistance of the starter solenoid is the << less the the defect upstream.

It shouldn't matter if the yellow wire were connected or not or whether there's a defect in the solenoid or a direct short to ground (smoke is pretty obvious). Connecting a voltmeter to the circuit at that location measures the available (potential) voltage at that location. Either the yellow wire delivers it or it doesn't.

Sherwood

[1411506]

Sorry...I'm not making this very clear....The problem is that I have no power at the solenoid when cranking.
While troubleshooting, this is what I found - instead of a direct conection with the solenoid, the yellow wire comes from the ignition switch in a bundle of wires to a 14 pole connector in the cdi box area. When cranking, I see 12 volts at the connector. So, the ignition switch is good.
The yellow wire then goes with a bundle of wires to a second 14 pole connector. In order to see whether I was still getting power at that connector, I unplugged it - and cranking did produce 12 volts at the yellow wire in the connector. From the second connector, the yellow wire splits - one branch goes to the solenoid, the other to the temperature time switch.
This is where it gets weird.....when I plug the connector back in, I no longer get power on cranking.
So, with the second connector unplugged, I ran a jumper wire from the yellow wire terminal on one side of the connector to the yellow wire terminal on the other side of the connector and cranked it. The starter worked.
As soon as I plugged the second connector back together, and removed the jumper, the starter stopped working.
So, one of the other wires in the connector is somehow affecting the yellow wire when the connector is plugged in.
I tore off all the electrical tape from the wires (from the second connector back)and could see no shorts. The only thing I haven't done yet is remove the alternator to see if those connections are somehow bad, although I still see no reason why a bad connection at the alternator would cause the starter not to work....

[rick-l]

Originally Posted by 911pcars

It shouldn't matter if the yellow wire were connected or not or whether there's a defect in the solenoid or a direct short to ground (smoke is pretty obvious). Connecting a voltmeter to the circuit at that location measures the available (potential) voltage at that location. Either the yellow wire delivers it or it doesn't.

Sherwood

What voltage would you measure at the starter in each case below?

[rick-l]

Originally Posted by 1411506

.....when I plug the connector back in, I no longer get power on cranking....

With the wires connected can you probe the back of the connectors to see where the 12 volt drop is?

[911pcars]

Originally Posted by rick-l

What voltage would you measure at the starter in each case below?

Rick,
My statement, "Connecting a voltmeter to the circuit at that location ("Voltage_at_starter") measures the available (potential) voltage at that location" remains true in both of your examples. The voltmeter will read available voltage, whatever that is, measured at V1 and V2 in yellow circles. However, the voltage is lower than battery voltage because of the 1000 ohm resistance at the switch.



In your diagram, what does the R3 load represent?
Is ".op" relevant to this circuit?

Sherwood

[rick-l]

R3 represents the winding resistance of the starter solenoid. (i guessed about 2 amps)

In your picture V1 will read 0.06 volts and V2 will read 12 volts.

On the other hand if you replaced the 1000 ohms with the impedance of the battery and the contact resistance of the switch (<< 1000 ohms) the voltage across the solenoid (R3) would be about 12 volts.

The .op is just a spice command to find the DC operating point. It is simpler to do that than use a calculator.

[Beetle Bailey]

[QUOTE=.
This is where it gets weird.....when I plug the connector back in, I no longer get power on cranking.
So, with the second connector unplugged, I ran a jumper wire from the yellow wire terminal on one side of the connector to the yellow wire terminal on the other side of the connector and cranked it. The starter worked.
As soon as I plugged the second connector back together, and removed the jumper, the starter stopped working.
So, one of the other wires in the connector is somehow affecting the yellow wire when the connector is plugged in.
I tore off all the electrical tape from the wires (from the second connector back)and could see no shorts. The only thing I haven't done yet is remove the alternator to see if those connections are somehow bad, although I still see no reason why a bad connection at the alternator would cause the starter not to work....[/QUOTE]

Have you checked the pins in the connectors. It could also be the first connector is not making good contact internally (male/female)or is pushing away or corrosion. Things check good with sharp points probing but are completely different with rounded pins.

[1411506]

Yep - actually there is a cap on the connector - this cap comes out and the pins can be removed individually. We removed the yellow wire pin and stuck the multi meter in and still no voltage on cranking. The multi meter was in the same place as it was when the connector was unplugged and registering power earlier.

Originally Posted by Beetle Bailey

Have you checked the pins in the connectors. It could also be the first connector is not making good contact internally (male/female)or is pushing away or corrosion. Things check good with sharp points probing but are completely different with rounded pins.

[911pcars]

Here are some early factory wiring diagrams:

http://members.rennlist.org/911pcars/WiringDiag.htm

Mine has two fuse boxes with 8 fuse positions inside. Your electrical system may be different. A yellow wire from the ignition switch (item 2) connects to the starter solenoid (item 1). This is the wire that energizes the solenoid during cranking.

There's another yellow wire at the solenoid terminal that continues into the engine compartment and is the circuit you have an issue with since it either disables the solenoid (harness connected) or allows the starter to crank (harness separated).

According to the wiring diagram, this circuit goes to the following parts:
70 Time limit switch, then parallel circuit to item 66 (starting relay switch)
71 Temperature switch (start)
72 Temperature switch (start assist)

62 is the multi-pin harness connector (your connect/disconnect point)

My carbureted 69T doesn't have this circuit from the solenoid. I'm not an MFI guy, but I suspect the above parts are for cold start MFI enrichment. If yours is MFI, I'd locate and identify each part, then disconnect the yellow wire to each in turn to help isolate the source of the malfunction.

Hope this helps,
Sherwood

[1411506]

The auxiliary sarting relay was bad - replaced with a known good one and the starter started cranking.
Thanks to everyone for their help!
Rob