Put the car up on jacks again and see if it starts if so look for a loose wire shorting out when the car is on the ground. Just my 2 cent worth.
ichard

Thanks for all the input guys I appreciate getting second opinions when all I want to do is yell at the car "you just started 5 minutes ago!!!"

I did put her up on jacks again and everything is secure and where it's suppose to be

This could be an intermittent ignition switch problem.
Another thing to check would be the 14 pin connector in the engine compartment (left side) check all the connections in it. Dab some dielectric grease in there and plug it back in.

Hello There:

I am coming late to this party, so I apologize for being late.

Anyway, I am with Richard Burns on this one....if your car will start when it is up on jack stands, but it will NOT start when you put it back on the ground/road/hella port, then there is some wire or electrical part that is grounding out on the body of the car. I guess the proper wording would be "there is something grounding against the body of the car."

One dumb question...has this car taken on salt water? For example, has this car gotten water inside of its compartment? The reason I ask is, that some of the wiring could have gotten contaminated by water corroding a wiring harness running along the tunnel.

Just a thought and I am certainly no expert, but I do hope this helps solve this annoying problem you are experiencing right now.

Great idea about the water. The car had about an 1 1/2 of standing water in it a few months ago during the rains here in LA.
Do you know or have any ideas about checking for shorts in the the tunnel?
It's been dry for weeks and has not given any indication of going bad. It even ran great when it had water in it

Well, here is what I know about our cars: They both have a computer brain that is under the passenger seat.

My thought pattern with regard to the above is this:

Water is a conductor of electricity.

Water may have gotten into the brain (ECU) and is shorting the circuit board that lives inside of it. Another thing that came to mind is that when the car is on jack stands, the rear of the car is up in the air higher than the front, which would make the water that is still inside the car, or inside the brain move forward, or rather pool towards the front of the vehicle. So, thus, the reason for the car to start when up, but not when it is level since the water is now pooling along the entire bottom of the brain box.

Although most experts would probably agree that the brain (ECU) box would need to be replaced to test this theory properly.

Is there someone nearby that has the same year 911SC? Their brain box could be swapped out with yours to see if the car starts. Or rather, swap the brain from your car into a known good 911SC 1983 or 1982 only and see if the car starts. I have done this on 944s before to test.

Another test would be to check electrical conductivity/resistance with each of the terminals/plugs inside the harness connector. This connector is the big plug like apparatus that connects to the brain itself; there are write-ups within the Bentley Service manual on how to test each respective wire for continuity.

Seems you have ruled out the grounds, the solenoid and the battery. I was quite sure it would have been your ground.

As a few have pointed out it seems that the next most likely thing is an intermittent issue with your electrical portion of your ignition switch.

A common problem here is corrosion or wear. One way to possibly check is to wiggle the key, or hold pressure on the back of the switch while you are turning the key to see if it engages. If it does you will see that, the switch is the problem (or part of the problem) and needs replacement.

Not at 12 volts. And the computer has nothing to do with the starter circuit itself.

Connect a test light to the starter solenoid and put the test light inside the car.

If you turn the key to 'crank' and the light is 'on' but you don't have starter action then your starter is the issue. If you turn your key to 'crank' and the light is off then the key switch is not working and you need to add a 'push to start button', or replace the switch.

Thanks
I have installed a new switch which of course I'm assuming is good. I am getting 12.4 volts at the starter switch when I have the car in the air and crank it. I am going to run a direct line from the battery to the starter switch (terminal 50) and see if that starts it. I can do this while the car is in the air and also after I drop it.
I'll let you know.
It's freakish because I replaced the ground strap and she fired right up, dropped the car came out and she wouldn't. I'm starting to think I have an intermittent ground problem somewhere

I'm getting 4.4 volts at the 14 pin connector in pin number 1. I'm getting 2.4 volts at pin number 3. Both are when I turn the key to the start position.
I made a momentary switch and hooked it up directly to the terminal 50 on the solenoid and she started right up. So I know I'm good with grounds at the starter and trans.
How do I check back at terminal 50 to see if I'm getting 12 or 4 volts there when the key is turned to the start position. The unit is sealed

Before you had 12.4 volts at terminal #50 while cranking. That goes through the 14 pin connector at terminal #1 - something is intermittent, and that makes it hard to find.

The Yellow wire, terminal 50 at the switch and at the starter, has a long route. It goes from the switch, through a bulkhead plug, to the 14 pin engine compartment harness, and on to the starter. Disconnect the plugs and clean and separate the pins with a razor blade. The yellow wire is also tapped into the heater ventilation switch. You need to trace, unplug, and clean all of the connections.

Are you sure your car didn't have air conditioning at some point in its life?

You are probably only going to be able to do that by taking the whole switch and locking assembly out, then use a pointed lead to squeeze up in there from the back.
I think you are going to find that the connection between the electrical portion and the plug are not always making good contact.

If and when you do this wiggle it around to see if you have a good solid connection or if it is intermittent. The wire contacts in the plug must be raised high enough to make a good connection, if they can wiggle around or pull in and out it could result in the symptoms you are having.

I am not sure of a fix for this other than a new receptacle or perhaps some epoxy.

Oh the car had air conditioning. The car came fully loaded but went on a huge diet when I bought it.
I've got 12 volts coming in to the 30 terminal on the supply side of the ignition switch, I just can't figure out a way to test terminal 50 out while it's in the start position.
And your right I did have 12.4 at the solenoid last week and that is what is driving me crazy

Also Its a brand new electronic part of the switch from our host

There's a relay in the smugglers box that is a known problem area for these cars.

There is nothing in the smuggler box for the last 5 years but a small space saver battery.
I think I have bigger problem with the electronics!
I cleaned the grounds in the engine and took the interior out and cleaned the ground by the ECU.
I got tired of the low voltage at the #1 in the 14 pin connector in the engine and could not figure out how to check terminal 50 of the ignition switch so I ran a momentary on switch from the battery to the dash to the solenoid terminal. Turned the ignition on pushed the switch and she starter right up.
Then the new problems starter. The engine went to a high idle 2400 for about a minute then the idle dropped to 1100 and the engine started bucking and back firing and trying to give it a little gas only made it pop and buck and generally pissed off.
So I shut it down and am taking my wife out.
Any idea's as to what could cause the voltage lost at the 14 pin connector and cause all the engine problems I would love to hear them!

Thanks Guys
Steve

Can you post a schematic?

This is from another thread somewhere on this forum, sorry I cant remember who posted initially.

http://forums.pelicanparts.com/uploa...1302469021.jpg

Steve... Did you get it all figured out?

Shane... That schematic looks like it might have been from Warren Hall, post #5 at http://forums.pelicanparts.com/porsche-911-technical-forum/328342-starter-solenoid-wiring-question-where-do-yellow-wires-go.html.

Hi.
I haven't had any time to work on the car since my last post. It is sitting on jack stands in my drive way mocking me.
I am going to try and make some time today. Will let you know
Thanks