update - problem solved!
Many thanks to spidryell, John533i and spiderserie4 for the tips.
I am pleased to announce that by following the instructions in Step 3 The cold start and warm up system of Greg Gordon's and Eric Russell's wonderful L-Jetronic Troubleshooting Guide, I was able to diagnose and correct my cold start problem.
Pretty simple really. The fact that the CSI only opens if the TTS is operating properly and completes the ground to the CSI switch, was the key to the puzzle.
To begin with, I knew my CSI was not spraying when the car was cold, because I removed it from the plenum and held it in a clear bottle while my son cranked the starter with the ignition key. I also knew the TTS appeared to be OK, based on the fact that the resistance between each terminal and ground, and between both terminals, was within spec. Finally, following spidryell's advice, I verified that the blue wire going to the CSI had continuity to ground when the block was cold (meaning the TTS was properly in the closed position). I could have checked for +12 volts during cranking on the green/gray wire going to the CSI, but I didn't have a helper handy, so I took a chance and bought a new cold start valve.
I managed to find one (made in Spain by BWD) at my local O'Rielly's for $120. Interestingly enough, it had BOSCH and 0 280 170 031 stamped into the housing.
Anyway, since I still had the clear bottle handy, after I attached the new CSI to the fuel hose, I stuck the tip of the CSI into the bottle and asked my wife to turn over the engine. A nice spray of gas flowed out into the bottle.
I put everything back together, waited a day, then turned the key. Immediate catch and idle! And thanks to the terrific help from this forum, I only had to buy the one part I needed.
Life is good.
'88 Quad - "Claudia"
Last edited by Norseman50; 05-06-2017 at 03:13 PM.