4ksq doesn't start when warm

[luis@odf.ucsd.edu (Luis Patino)]

Now that the list helped me so much with the overheating "problem" - thanks! - I
would like to ask you fellow audiphiles about my car's other significant annoyance.
The symptom is that if the 4ksq runs long enough to get warm and then it's turned
off and sits for more than a few minutes, it will absolutely refuse to start - no
matter how long its engine cranks. And crank it will, with plenty of juice, but it
will absolutely refuse to start.  However, if I let the car sit until it cools down 
completely, it will start perfectly, as it always does when completely cool. Other
than this problem, the engine performs fantastically, actually so well that I
wouldn't care about this annoyance except for the _hours_ it takes for the car to
cool down.

Did I sound stupid in my first paragraph? I hope so, because I did not want to
prejudice anyone with what I have figured and found about this problem, so that
in the - unlikely, I also hope - case that I am wrong, someone will be able to
tell me.

Of course I don't wait for hours until the car cools down. Since it has done this
or something very similar since I bought it 1.7 years ago, I quickly researched
the reason for these faults. Having eliminated lack of spark and pump-relay 
malfunction, I realized that fuel wasn't getting to the injectors when the car
was warm. I didn't know why until I couldn't start it at a gas station after
fueling. There someone who knew VW's showed me that if I opened the bolt on top
of the KE-Jetronic fuel distributor and let fuel come out, the car would start.
He didn't know why, but it sure worked. However, seeing the bubbles and pressure
that got relieved along with the fuel (I guess doing this was a fire hazzard) I 
realized that gasoline was boiling somewhere in the lines and that the resulting
vapor was blocking the flow of the fuel. Somewhere I had heard of a condition called
vapor lock, so, I thought, that was it. Later, when I got my Bentley manual, I saw
the series of checks that have to be done when a warm engine doesn't start. I was
supposed to check for how well the KE held its residual pressure, since it's 
precisely this pressure that prevents the fuel from boiling. Thus, what it boils
down to is that the pressure is leaking somewhere in the injection. At that time
(and also now!) I didn't have fuel pressure gauges, but searching the web for 
KE-Jetronic, I found an auto encyclopedia site that explained how KE-J works, and
explained that if the air-volume-sensor plate did not have the right play,
1.0 - 2.0 mm then the stop-screw o-ring would not seal and cause residual pressure
leakdown. It also mentioned all the other possible leaks, but since to check for
those I needed the pressure gauge, I went for the easiest cause of the problem
the one that cost nothing to fix, and sure enough the sensor plate had too much
play. Using the stop screw underneath the fuel distributor (I made the tool to
turn the screw by shaving the prongs of a minifuse), I adjusted the play, and bingo!
the car started starting - I had eliminated the vapor lock.

Unfortunately, last winter, the car started misbehaving again to the point that now
it doesn't start whenever warm. Luckily, since I learned to bridge the fuel pump
circuit at the relay connection, I bridge it now to let the fuel pump compress the 
bubbles instead of having to purge the bubbles through the top screw. Bridging the 
connection works almost every time except when the weather is hot. In those 
instances I have to both compress and purge many times before the car would start.
Thus, I can always get it to start, but have to put up with embarassment from
passengers and passers-by.

This time the cause of the pressure leak has proven more elusive, and I don't have
the testing gauge yet ($$$). The sensor-plate play is 1.1 mm still as I adjusted it,
so I guess that's out. However, when I checked the play last weekend, I discovered
that after running the fuel pump to pressurize the system (to measure the play
correctly) a mild fuel odor came from underneath the plate, that is from the air 
intake box. So I lifted the lid with the KE assembly on it and felt with my fingers
around the plunger lever from where I picked up brownish goo with strong fuel odor.
Thus, the leak is probably from the o-ring that seals the plunger in the fuel
distributor.

Should I replace that ring? There are no other obvious fuel leaks on the outside
of the fuel lines, pump, filters, etc. Can someone in the Southern California
(I live in San Diego) area lend me the fuel pressure gauge? Anything that I might
be missing? Has anyone with the same problems corrected them successfully?

Thanks!

Luis

4ksq 132k mi