Who's working on it in Chattanooga? Bavarian Auto in Chattanooga worked on mine. They seem very knowledgeable. Family owned with 38 years experience on Porsche.

 

When you tested the parts they worked , so did all the parts . Then something didn't work .
Just because you tested something while it was working does not prove that it was working when it failed .
Electrical parts can over heat and stop working . When they cool down they might start working again .

Try unplugging one ignition switch before starting up the car .
Does the motor run and keep on running ?
If the motor stops running after a bit , unplug the one switch and plug in the other , try to restart the motor .

 

this is too simple for it to be the case, but try disconnecting the battery (both cables) and disconnect the negative cable also from the body connection. Then clean all the connections thoroughly. Then reconnect everything and see if this doesn't solve your problem. I've found that German cars are very bad for have corroded contacts, and low voltage will sometimes yield your symptoms.

 

It is important that you test the fuel pressure immediately when you are having the issue. Disconnecting a line on the fuel rail and seeing if gas flows out is an inconclusive test as far as confirming adequate fuel delivery.

I have twice seen this problem (not on a 964, though) where the problem was a clog on the supply side of the fuel pump. When the car sits, fuel will trickle through the clog and fill up the line. When the car starts, the pump will "pull" the gas in the line between the pump and the clog point and run fine. Once that gas is gone, the pump must suck gas throught the clog, which it may not be able to do a rate equal to the demand from the injectors, resulting in voids in the supply line. The problem will be compounded if the fuel pump gets hot, which can cause the fuel to start flashing off inside the pump, as it is not fully primed with liquid..

 

Thanks for your suggestions. The latest information after sending the DME to be tested, replacing the DME relay and speed sensor still no start. This weekend I installed a pressure gauge on the fuel rail and have 45 pounds pressure. I placed a jumper on one of the distributors (the belt is intact) to view spark and an LCD lamp on an injector connection to view pulse. The car started and ran strong for about 5 minutes while I observed a strong spark and a steady injector pulse. The car began to miss becoming more frequent until it finally died. During this period I noted that when it missed I was simultaneously losing spark and injector pulse signal. There is some intermittent condition. When it cranks but won't start I observe both spark and injector pulse. Fuel pressure remains constant whether cranking or running.

 

Thanks for your suggestions. Yes it is an intermittent electrical problem. The rear fuse box connections look new and I understand the 964 has no ground strap as the earlier 911's; at least I couldn't find it and Pelican parts said the 964 did not have one. The latest information after sending the DME to be tested, replacing the DME relay and speed sensor still no start. This weekend I installed a pressure gauge on the fuel rail and have 45 pounds pressure. I placed a jumper on one of the distributors (the belt is intact) to view spark and an LCD lamp on an injector connection to view pulse. The car started and ran strong for about 5 minutes while I observed a strong spark and a steady injector pulse. The car began to miss and became more frequent until it finally died. During this period I noted that when it missed I was simultaneously losing spark and injector pulse signal. There is some intermittent condition. When it cranks but won't start I observe both spark and injector pulse. Fuel pressure remains constant whether cranking or running.