911 wont start...Again!! starter cable?

[cabmandone]

Yep... yellow terminal. Those two smaller wires go to a smaller terminal that energizes the starter solenoid. Check red lead to yellow wire and black lead to ground at the ground strap.
The two larger nuts in the pic top one has a red wire and should have a hot wire from the battery. Bottom nut has a wire that goes into the starter. First check battery voltage. Red lead to large nut with wire from battery (wire isn't pictured in that picture) black lead to ground. Then with starter engaged check the voltage at the large nut that sends power to the starter motor.

[sugarwood]

I don't see a smaller terminal
I don't see 3 studs, just 2 of them, and they are the same size.

What is the bottom nut?
I see 2 studs that are side by side.
Did you mean left/right, not upper/lower?

[jgurnari]

I push-started the car to get it to the mechanic, once there I turned it off when I tried starting, it started!!
WT Heck!!? Been doing this after New started and fixing loose ground wire

[jlex]

Again, I'm recommending you REPLACE that braided ground wire, not just clean or tighten it. 10 minute job that has a good chance of solving your problem IMO...

[BK911]

My guess:
Parasitic draw on battery.
Remove negative wire on battery.
Set meter to milliamps.
Connect amp meter between wire and battery.
What is the value?

[jgurnari]

Can I troubleshoot the ignition switch? That possibly the problem... I did noticed it is riveted in.

[cabmandone]

When you try to start it each time do you hear the clicking sound like the solenoid is engaging?

[jgurnari]

Nick, yes there is a click. then i can try it later or another day and it starts

[jgurnari]

Nick, I can also push-start

[proporsche]

jgu..have you check the wires as i have mentioned take a picture of the wire going to the back of the ignition switch plug and show us so we can see..
Ivan

[PTRL HD]

Sounds like a similar issue as what I'm going through. Do you hear a "whir" of the starter motor spinning without engaging the engine? Have you tried replacing the DME relay?

I've been fighting my issue for a couple of years. I have another sports car so I haven't been laser focused to get this fixed. Plus, it always runs when pushed so other than a little embarrassment it is more of an inconvenience than anything. Shortly after it started happening I had a repair shop I've had good luck with in the past (but that is a 1.5 hour drive away) look at it. They cleaned the ignition switch and it seemed to start better. It had been intermittent, so that could have just been a placebo effect as it started happening again shortly after. A local repair shop replaced the starter which made it seem to happen less often, but still an issue, so I replaced the electronic portion of the ignition switch. Again, seemed better short term before not working. I replaced the DME relay and it worked perfect for about 20 drives, then started acting up. Somewhere in there I cleaned all the grounds I could find. It has been getting worse with time, finally getting to the point where it typically doesn't start. Over this winter it hasn't been starting at all. I replaced the battery and transmission ground straps (no change) and battery (no change). I was going to install an ignition bypass switch I'd purchased because I was sick of dealing with it and getting less and less concerned about the potential theft risk. While looking for that I saw an extra DME relay and thought I'd give that a try. Fired right up. The car is still on jack stands for brake/bearing replacement so I haven't driven it, but I've attempted to start it at least a dozen times and it is still working. From what I've read the relay's can be unreliable so I'm thinking my first replacement may have failed quickly. I will still be parking at the top of inclines facing down out of caution for the foreseeable future, though! Also, going to follow this thread for additional steps to take should it come back.

And, yes, I realize I should have been testing the voltage throughout. That is another reason I purchased the bypass switch, so I could engage the starter remotely for testing since I tend to work on it at odd hours when no one else is available to help.

[sugarwood]

Originally Posted by sugarwood

Dan,
Can you recap the testing for voltage drop?

Is this right?

1. DVM is set do DC Volts
2. Black DVM lead connects to positive battery cable at the starter?
3. Red DVM lead connects to positive battery cable at the battery?
4. Crank car.

What should peak value read if the cable is good vs. bad?
Good means voltage drop of .5v?
Bad means no voltage drop?

Tried to learn about voltage drop again.
I think I was accurate above.
The key for voltage drop is to test while current is flowing.
Otherwise, you can read 0v (12v at both ends of the cable, even if there is an issue)

https://www.youtube.com/watch?v=DfLyh43iihM

[4495]

I had a similar or maybe same problem recently. Just a click, then a few days later it might start or it might just click again. Sunday I went to check the ground on the starter so the first thing I did was to remove the negative ground from the batter post, the damn thing almost came off with just one twist of the nut. Tightened it back up and the car sprung to life. I love my 911 when it’s working like God intended.

[kltarga72]

What is most needed when energizing the starter motor is current flow. Current has to flow from positive side of battery to solenoid (large red wire on solenoid) to starter, through field winding, brushes, and commutator, this makes the starter motor spin. Then current will pass through the starter motor case which is bolted to the engine. Current has to flow back to the negative terminal of the battery. You need a good clean case connection at the starter motor and engine.

As someone previously mentioned you also need a good ground strap connection at the transmission. And of course you need tight terminal connections at the battery. Any loose, dirty, rusty, corroded connection in this current path will increase resistance which will lower your current

You can make voltage checks and get the 12vdc your looking for but that does not mean you have complete current flow.

Since you can push start the car your problem is in the starter motor circuitry.

Hope this helps

Lash

[kltarga72]

I meant to tell you that the solenoid also has some type of actuating device that pushes the pinion gear on to the ring gear. Sort of hard to check because of the location of the starter. If you could somehow put your hand on the starter and have someone turn the ignition key you should feel the pinion try to engage. You may need to pull the starter motor and bench test.

Lash