Had exactly the same problem myself couple of wks ago. Cleaned every terminal, all grounds and also the starter mounting points. Fired up better than it ever had right after this. Pay particular attention to the solenoid + post & the + feed ring termination. A useful doc I used for troubleshooting:

http://www.type-911.co.uk/images/general/text/Starter%20System%20Troubleshooting.htm

Hope this helps.

[b/"..Voltage from battery- 12.9V
Voltage at main lead at starter-12.9V
Voltage at "solenoid" lead when the key is turned to start postion-9.4V..."[/b]

Gary,
Based on your test numbers, you may or may not have an electrical problem. The starter solenoid is but one "load" on the branch circuit. There is also the starter motor that is (should be) running every time the solenoid is energized. Thus, if you checked the voltage at the solenoid lead when cranking, the 9.4 volts you read is the normal available voltage from the battery during cranking. This is because the starter is placing a large load on the battery. BTW, the battery is fine if above 9 volts while cranking.

If, however, you checked the available voltage at the solenoid lead while cranking and the starter motor remains idle (there is no voltage drop from the starter), then there indeed is a voltage drop in the solenoid circuit, enough to prevent the solenoid from energizing. However, one can't normally isolate the solenoid circuit unless you disconnect the battery cable from the starter and insulate it or physically remove it from the starter, then test.

I'd suggest verifying the ground cable(s) and all electrical connections are okay as others have suggested. Check for voltage drop throughout the circuit, not just up to the load (multiple grounds are fine). I can't imagine all the different starters you've tried all had faulty solenoids. How about trying this? Connect a remote starter switch to the solenoid and crank the engine using this temporary switch; one jumper clamped on the solenoid terminal, the other on the battery cable on the starter motor. If the motor consistently works with this setup, you know the problem is somewhere in the solenoid control circuit (a solenoid is basically a large relay with a mechanical plunger).

Does the starter freeze up all the time or just when the engine is at operating temperature? A common affliction in later Porsches is engine heat that soaks into the starter motor; the armature grows in size due to the temp. increase and creates a lot of drag (actually rubbing) as it attempts to rotate; sometimes it won't rotate at all. The hammer trick some people use sometimes frees up the armature. Placing a wet shop towel on the hot motor or a spritz of water from a spray bottle may also help.

Hope this helps,
Sherwood Lee
http://members.rennlist.org/911pcars

Things get more interesting- or confusing. Sherwood- to connect the remote starter switch I just need to jump it between the hot lead on the starter from the battery to the yellow solenoid lead on the starter, correct?
Well.....
I cleaned off all the connections I could find- at the battery, at the 14pin connector in the engine compartment and at the starter-- no change- car no workee.
I then ran a set of jumper cables from the battery directly to the starter- car started fine. Disconnected the jumper cables- starter doesn't work. I did this several times. I then disconnected the ground- running just the pos lead from the battery directly to the starter- the starter worked fine, and didn't work when I disconnected it.
So, I thought I must have a bad cable from the battery to the starter- and just as I thought about it- the car started working normally. Right now it starts fine- and I didn't do anything or truely find the problem yet. Now when I start I get less than a 500mv drop from the battery pos terminal to the starter- so that lead has either fixed itself or I have some other problem. My present guess is that I have a bad connector on the starter cable from the battery- but they look ok, and nothing changes when I twist and pull on them.
I think I'll have to wait until it stops working again, and go at it some more. It is now working fine, and everything measures ok?
Maybe a halloween haunting.
These intermittent problems drive me crazy- as I never know when I can trust the car.
Thanks again for your help, has anyone heard of this thick cable going bad??
Thanks again for your help.
Gary

Gary,
It sounds like you isolated the main cable to the starter as the source of the malfunction. You now only have to look at two places; the ends of this cable. Sounds like a poor connection that's causing the intermittent starting.

Sherwood

Yes I did clean the grounds- but no change. When I used the jumper cables directly to the starter it also worked if I only used the positive jumper, but did not work if I only used the neg or ground jumper- so I am thus assuming the ground is not the issue.
The cable ends look ok- they are not loose or anything. Now that the starter is working- jiggling and moving the cable from the battery to the starter doesn't do anything- so I think I will have to wait for it to fail agian so I can look for voltage drops along the cable.
Thanks again for all your support
gary

Ron....point taken:rolleyes: