I've still got a sluggish start although it is improved somewhat after I've done plugs, leads, rotor arm, dizzy cap and a vac hose. I have an '86 K jet EV engine. I wanted to get hold of a new thermo time switch but it aint exactly cheap and was wondering it you could advise how I could check if it is actually dead. The part number is 043 906 163A it's an **** to get hold of from Euro and GSF - they both have to order it in from bosch. Can anyone help?
clean up the wiring for the starter and the earthing in general. more current will get to the starter so it will turn over better
What do you mean by 'sluggish start'? Does the engine turn over slowly on the starter, or do you mean that it doesn't run well when it's just started?
it doesn't catch straight off, has to turn a few times, once it starts it hunts a little while warming up, only the first minute or so. This particularly the case when first starting in the morning. If it's warm from running not so long ago then it is much quicker to catch but not instant like I want it.
Leaky injectors would be high on my list. Is it any better from cold if you unplug the cold start valve?
It's certainly no better with the thermo time switch plugged in, this is what triggers the cold start valve so no different, it's not leaky injectors as it would explode into to life when it eventually caught and that doesn't happen. I reckon it's the thermo time switch which is taking ages to get hold of through the usual channels.
This part costs 70 with both VW and GSF, Euro will be the same no doubt, it's only a temperature sender!!! Is there any test to see if indeed this is broken, multimeter or somat?
Got a picture of the thing? If it's anything at all like the thermo-time switch used on Pierburg carbs, it isn't a temperature sender at all. If it is similar it probably has a little semiconductor heater inside it that warms up quite rapidly and opens/closes a valve by 'pinging' a disk of bi-metal against an o-ring. The resistance goes up very steeply with increasing temperature, so that the thing reaches equilibrium at a minimal current. Or it's different.
Can you see the brown plug sticking out of the inlet coolant fitting on front of block, that's the bas.
Its not just a temperature sender, its a timed switch - the colder it is, the longer the switch stays open. Really cold, ie freezing temperatures, it will stay on for around 10 secs. At approx 60 deg C (but don't quote me on this) it will not switch on at all. I think somewhere in the VW technical manuals, there is a graph showing the relationship between temperature and operation time. Its not a sensor - so no resistances, except the obvious approx infinity ohm - approx 0 ohm!
As far as I can make out, it is "F26" in Wiring Diagram 23 of Haynes (1081). It has a heater element, which the red/black wire powers (only while cranking, it looks like), and a switch which connects the green/white wire to ground when the thing is cold, but breaks that connection when it is warmer. The ground side of the heater part, and switch part is the case/flange. So if you haven't yet replaced it (scrappie?) you could test it if you have a multimeter. 1st test. With stone cold engine (first thing in the morning) put your meter on "Ohms" between the pin of the thermo-time switch that the green/white wire would go to if the connector was mated, and battery negative/chassis. Should read zero ohms. Then measure ohms from the other pin of the device (the one that the red/black wire would go to if the connector was mated) to battery neg/chassis. Not knowing whether its a simple resistance-wire heater, or a semiconductor type as I mentioned before, I don't know what the correct reading would be, but it won't be zero or infinity if the thing is healthy. Probably a few ohms. Then put the meter on "Volts d.c.", put the red probe on the pin of the connector that's on the end of the red/black wire, black probe on battery neg. Get an assistant to crank the starter motor, and expect to see 12V on your meter (while cranking). This checks the supply/wiring to the heater part. Lastly, start the car, let it warm up fully, then unplug the connector, measure ohms again between the pin that the green/white wire would connect to, and batt neg./chassis, and expect to read infinity ohms. This checks that the switch part does open when warm. Easy. P.S. If anyone has a known good set-up to validate these tests, or knows that I'm talking nonsense, please speak up! PPS. If the wire colours aren't what I've said, don't try this, 'cos I might be looking at the wrong wiring diagram. (Looks like they might be from your pic though.)
as said its not a temp senser at all, its a thermo-switch. It is closed when cold (i.e. current can pass thru it) and opens when either the heater inside warms it up or engine heat warms it up. 1 wire to the switch is a feed from the starter motor which is live when cranking (which is why k-jet cars have 2 spade wires to starter) the other is an earth wire from the 5th injector. The 5th injector gets 12v under certain conditions, and earths thru the thermo switch to the block, but only when the switch is closed/cold. edit: Pin G is the heater pin with a red/blk wire, pin W is the earth pin to the CSV with a green/wht wire.
