I left the key in the "run" position for slightly less than a minute and didn't feel any heat increase in the (new) resistors.

 

Why are you chasing spark ?? changing ignition parts when you KNOW the injectors are not firing. The FACT that it starts and runs briefly proves the spark is working. Full power 12v jumper to the small + wire on the coil would reconfirm it as well and completely rule out the resistors as a possible problem....
Focus on the injection actually lack of injection... the jumper wire on the fuel pump relay is either a clue or someone else's failed attempt to get it to run.

 

Not "chasing spark" I'm just following the troubleshooting flowchart in the factory shop manuals, as well as the suggestions provided by the contributors to this board. What I haven't been able to get an answer to is the question I posted recently about the MAF unit (part #0280 203 015). Is there supposed to be a heated wire in the airstream in my car? Mine has none.
I've found a few photos online of the outside for the unit, but none down the throat.

 

No wire in your airflow meter.....simple barn door that swings in the wind.

 

the suggestion to jumper the coil + small wire was to rule out the resistors as a possible source of the problem. Also rules out the ignition switch cutting out in the run position. Also eliminates any starter wiring problems as the cause of the start then die syndrome.
Not sure what you mean when you say you "ruled out" the relays as a problem ?? especially if you have the fuel pump jumpered to run all the time ?
On that point be aware that leaving the ignition on for any length of time with a running fuel pump has the potential to fill a cylinder with fuel if you have a leaky injector and should the engine fire you can split a cylinder or bend a connecting rod very easily.
It can be a challenge when you adopt a none running car. Part of the mystery is figuring out what OTHERS did in their attempts to get it to run but you are more than halfway there since your car DOES run !! so you have compression , you have spark, it has correct timing enough to start, now why are the injectors not pulsing ??

 

I installed 2 new resistors purchased this year from 928 Intl, along with a used coil from same. You're right that I'm dealing with someone else's "modifications". Glad (but kinda disappointed) that there's nothing wrong w/ the MAF meter. Gotta continue the troubleshooting.

 

I was THIS close to putting this beast on Craigslist or E-Bay, and was trying to get the windows up and tight before banishing it to the outdoors, albeit under a car cover. Had the console partly disassembled to check the window switches when I saw a decidedly non-Porsche bit of electronics. Turns out this had an aftermarket security system installed, and I removed an inline fuse. Got bold and tried to start it. After starting and stalling as per usual a few times, it then began to run for more than 5 seconds! Anytime I tried to use the throttle it would stall. A couple attempts later while avoiding the pedal, it stayed running. I let it idle for a minute or so, and gently moved it forward and backward. Bliss! I was able to use the gas pedal after a bit, and moved it out of the garage under it's own power!
After shutting it down however, it wouldn't restart. Cranked like a fiend, no hint of firing. A day later, I was able to duplicate the same start/stall/run events, with it still not restarting after shutdown. Understanding that the fuel in the car has got to be compromised at best, it still doesn't sound like bad fuel/clogged injectors, etc. Nevertheless......the beast has bought itself a reprieve.

 

Had a local track car ('84) fail to start after it was all loaded up for the ride home. When loading the track tires in the hatch the owner nudged one of the terminal connectors in the spare tire well. Couldn't hurt to see that they are tight.

 

Did you replace the thermotime switch?

 

No, but I checked it according to the troubleshooting guide in the manuals, and it's within spec.

 

I ask because you referenced that the troubleshooting guide mentioned MAF instead of AFM, so I figured you had wrong guide. Thermotime will cause stumble no start at temps sub 65 degrees. Not same as Temp II. Cars with MAF do not have Thermotime sensor, which runs axially into water bridge.

I have had extensive experience with the 84 USA, having brought two of them back from the dead.

 

I tend to agree with you that my current issue is temp related. When I've been able to start it and get it to stay running (after half a dozen tries), I'd get greedy and let it run for several minutes, figuring that more injector cleaner running through the system is better. Then I'd get no restart at all for the rest of the day. Yesterday after getting it running I shut it down and not running long enough to raise the temp, I was able to restart a couple times. Gonna order the thermotime switch now!

 

Its one of the sensors that has a finite life.

Have also had a car that had a corroded wire inside the brain cover. Very difficult intermittent failure to find. It was about the only thing serviceable for a layman inside that box. It was causing loss of half the injectors intermittently, taking the car down. typically it would run a while very well, then stumble to the side of the road. Repeat attempts to start sometimes gave a rolling stumble / stall.

Stay with the troubleshooting, these cars are worth it.

 

I found a thread on bypassing this switch that was suggested at the bottom of the thread (till I get a bargain on a new one), and it works! Pull off the connector, ground the "not G" (I can't remember what the letter designation is) input. For anyone else having a similar issue this is a quick and simple mend....not so much a repair.

 

Good news!

Brian.