Hi guys, just trying to work out the electrical fuelling system on a Mk2 16v. I'm just trying to clarify exactly how the thermotime switch works. I've just worked out it controls cold temp enrichment using the cold start valve but I need to know under what conditions it operates. I'm thinking it's operated for 8 seconds when the engine coolant is below a set temp but then is open for ever after that, so it only ever works for 8 secs after starting. Is this correct? Cheers, Joe
Sounds about right Joe. Good K-Jet info page, thanks to 800g's Also found this "Once you're pointed in the right direction, you can perform some specific checks to locate the offending component. I'll use a typical Volkswagen system as my example, but most of what I say here applies to all K-Jetronic systems regardless of the make of car. To test the thermo-time switch, it's necessary to first make sure that the coolant is below 95 deg. F. Remove the coil high-tension wire from the distributor, then connect it to ground. Unplug the connector from the cold start valve, attach a test light to the connector's terminals, then crank the engine. The light should go on for several seconds, then go out. In cases where this doesn't happen, the thermo-time switch or its circuit is faulty. If you keep operating the starter on a car with a hot start relay, the light will blink on and off at regular intervals" Edited by: G_V_K
Cheers Gary, yeah, is what I thought. Just makes the point of the diaphragm pressure valve even more pointless, it enabling the cold start valve under acceleration with the thermotime switch enabled. So it's used in the 8 odd seconds after you've cranked the engine for acceleration enrichment. Mmmm, useful Joe
Okay, I've worked it out now. The thermotime switch will operate the cold start valve for 8 seconds "worth" of cranking the engine. After that it will shut off so stopping the cold start valve from flooding the engine. Once the car is started, the thermotime switch is no longer heated by the starter so it cools and switches again into cold mode, this time operating the cold start valve if there is high inlet manifold vacuum, i.e. accelerating. This uses the diaphragm pressure switch to detect the vacuum. The thermotime switch only stops for good when the engine reaches a set temperature where all the cold functions stop, cold start and cold acceleration enrichment. Right, got that off my chest, methinks I'm gonna write an FAQ on all this stuff so I don't forget Joe
So, If we had a problem with the thermo time switch not switching off when warm, we could have the engine being flooded by the cold start valve Pretty sure I've replaced one on an RST in the past for that problem I know you can do a resistance test on them in warm water, got it written down at work IIRC..
