Thermotime Switch (TTS) and engine flooding

Hi all,

The engine has been flooding and won't start. I removed the plugs and dried them off, checked the dizzy cap and tried again- strong smell of fuel and engine flooded again.

This time I took the connector out of the thermotime switch (TTS) and it started first time.

However- the TTS has been replaced less than a year ago and was a genuine VAG part.

Does anyone know what would case the TTS to fail again? Could it be something else at fault that is masked when I disconnect the TTS?

Many thanks.

Could it be that the 5th injector ( the cold start injector) is actually at fault and not the TTS? In which case is there a way to test the TTS using a multimeter?

Thanks.

Must be faulty again ? Runs as you no the 5th injector and this must be flooding the engine . Strange as it only works when cranking the engine ?  :dontknow: Its a switch so you must be able to simply check it using basic tools .

Function
When cold-starting the engine, voltage is applied to the start valve and the thermo-time switch through terminal 50 of the ignition-start switch. If the cranking process takes longer than between 8 and 15 seconds, the thermo-time switch switches off the start valve in order that the engine does not "flood". In this case the thermo-time switch performs a time switch function. If the temperature of the engine is above about +35°C when the starting process is commenced, the thermo-time switch will have already open-circuited the connection to the start valve, which as a result does not inject extra fuel. In this case the thermo-time switch performs as a temperature switch. Voltage from the start-ignition switch is still present at the control relay, which switches on as soon as the engine runs. The rotational speed reached when the starting motor cranks the engine is high enough to generate the "engine running" signal which is taken from the ignition pulses coming from terminal 1 of the ignition coil. These pulses are processed by an electronic circuit in the control relay, which switches on after the first pulse and applies voltage to the electric fuel pump, the auxiliary-air device and the warm-up regulator. The control relay remains switched on as long as the ignition is switched on and the engine is running. If the pulses from terminal 1 of the ignition coil stop because the engine has stopped turning, for instance in the case of an accident, the control relay switches off about 1 second after the last pulse is received. This safety circuit prevents the fuel pump from pumping fuel when the ignition is switched on but the engine is not turning

Thanks Chudd. So if the TTS was fault it could be opening the 5th injector causing the flooding, and when I disconnect the TTS this stops occuring?

As this is a new TTS there must be an underlying fault somehwere… I have noticed that the fuel pump relay on the fuse board runs extremely hot- so hot I replaced it, but the new relay runs just as hot and is causing som warping of the fuse board. I wonder if this is all linked somehow?

Dont think so , from experience hot fuel pump relay is due to strain on the pump , there was a large post recently about it .

So if the TTS was fault it could be opening the 5th injector causing the flooding, and when I disconnect the TTS this stops occuring

I would agree .

Cheers …….

Cheers. Funnily enough I replaced the fuel pump recently, but the relay still runs hot. I'll check out the post you mention.

Unfortunately still doesn't answer why the TTS would fail less than a year after it was replaced!

I'm selling it in April so I guess I might never find out!

ransom question, but what colour is the thermoswitch on the front of the head? it should be brown. reason i ask is i was working on a cabby gti most of a day trying to get it started, till i eventually noticed this switch was white.  what he had done is fitted an early mk2 digifant engine block without swapping the correct thermoswitch over.

It's brown!

On another post someone was talking about a leaking CSV causing the starting problems. Anyone know how to investigate? Bulb in haynes approach?

pull the 5th inj off the inlet and point it into a bucket, crank it over on the starter and it should spray fuel, wipe the tip then leave it for a bit and make sure it doesnt drip