Thermo Time Switch

Just unplug the cold start injector before doing the warm restart attempt (that simulates a working TTS). If it restarts well = justifies more examination of the TTS system; if still a difficult warm restart = problem is most likely not in the TTS system.

 

Yep, that's the cold-start injector.

 

You mentioned a lot of new parts in your first post.

I think you are having a problem with your fuel pressure. My guess is that the accumulator or one of the check valves is not holding and you are getting vapor lock. That's why your car will not start when it heats up.

 

Also...the tts is reading your engine temp. If it thinks your car is cold, it tells the cold start injector to come on.

If it was a problem with your tts, you could simply unhook the wiring connection to the cold start injector and your car would start with no problem.

That is why your issue is with the fuel pump check valve, accumulator, or a loose connection.

 

I said it again earlier working on k-jetronic cars for more than 30 years: the most common failure for hard hot start are leaking injectors. The initial fix is really easy:

while the car is runing firmly ( but still gently) "tick" the inh=jectors one by one. In many cases you even will notice a better idle. In adition you can use injector-cleaner as addition to your gas.

Loss of pressure due to a bad accumulator will seldom cause this issue ( I ran k-jetronics WITHOUT them!) Loss of pressue due to leaking injectors is in many cause the real rootcause. ( and by leaking they flood the engine adding to the hard start)

Of coarse replacing is the ultimate solution but slapping them is in many cases enough to solve the problem.

 

You've replaced a lot of parts, but you really haven't made any measurements to determine the root cause. Two things I would do before deciding what to do next:

1. Confirm/deny spark is occurring during the "engine cranks over OK but doesn't warm restart" events (it's probably OK, but it's really easy to rule this whole subsystem in or out), and

2. Measure the regulated supply fuel pressure after warm engine shutoff to see if it reduces too quickly (it should stay ~3 bar for twenty minutes IIRC)-- in addition to the accumulator, A) there is a seal inside the pressure regulator section of the K-Jet fuel distributor that can cause the fuel supply pressure to (wrongly) fall to zero after warm engine shutoff if it fails, and B) you've replaced the fuel pump (which should've replaced the check valve on your model), but there are two different Bosch CIS fuel pumps -- the early stock one for your model has a non-replaceable internal check valve, and a later one that has a replaceable external check valve -- as it has been reported here before, a mechanic can wrongly replace the early type CIS fuel pump with a later type CIS fuel pump with a little plumbing change and (wrongly) leave out the check valve completely.

Good Hunting!