Thermo time switch connector disconnected

Hello,
As I was looking to fix (another) issue with my 91 GTi cab I noticed the thermo time switch connector (black + green/white wires) was hanging loose in the engine bay.

I've only had the car for a few weeks so came to me like that and I don't know why it's been disconnected. I have - so far - not reconnected it as I haven't really had any starting issues.

The car usually starts cold after 2-3 seconds of cranking (this is UK temperatures ~20 celcius), sometimes immediately. Same when hot although it tends to fire up quicker then but sometimes gets a stutter for a few minutes after hot starting and has come close to dying a couple of times. 

Why would the wire be disconnected? From what I understand, if it were connected it would shut off the additional fuel injection when the engine reaches a certain temperature? Is that correct?

Trying to wrap my head around the tests that people mention on other threads but I'm new to this so struggle a little to follow the logic. 

Many thanks,
Ben 

The thermotime switch control the 5th injector - when cold it lets it fire for a pre-determined amount of time (that's the 'time' bit) but when warm, it won't allow it to fire at all (that's the 'thermo' bit). With it disconnected your 5th injector won't be doing anything. Might be okay in this warm weather, but you might struggle starting it when it starts to get colder.

Thanks. I'm guessing someone might have disconnect if the switch was malfunctioning i.e. not shutting off and flooding with fuel? Any other reason why one might take it off?

I can't think of any other reason.
When it is cold there should be a circuit between the terminal fed by the green/white wire and ground - this effectively turns on the 5th injector. When it is hot, there should be no circuit. Guess you could test this with a multi meter - stick it in boiling water to test 'hot'.
The red/black wire is a heating coil  so there should be some resistance between this terminal and ground.
Basically, when you start the car cold, the switch is closed firing the 5th injector, power is also applied to the heater in the TTS, as it warms it causes the switch to open, turning off the 5th injector. When it warmed by the hot engine coolant, it's off. Pretty simple device really.

Right, so stick a multimeter in the green / white side of the connector and check for continuity to ground? What state of the ignition is this in? Just with engine running? 
What am I sticking into boiling water to test for hot? 🤔
The other wire in that connector is just black, I believe not red/black. So is that the one that powers the heating coil in the switch? 
Appreciate the 'simplicity' 😂 I'm just quite new to the world of wires, switches and relays. 
Ben 

Connect up the thermo time switch and see how the car starts when cold and hot.
If no difference leave it connected.

If it's lumpy when starting then to much fuel getting into the engine but that could also be from old leaking fuel injectors.

Might do that this week - just thinking it can't be a coincidence that the connector was detached so I'd be surprised to find it working just fine. Oddly, I wondered whether the stutter after hot start could be related but since the connector has been off since I've had the car the two things won't be related. 

Radler1 said

Right, so stick a multimeter in the green / white side of the connector and check for continuity to ground? What state of the ignition is this in? Just with engine running? 
What am I sticking into boiling water to test for hot? 🤔
The other wire in that connector is just black, I believe not red/black. So is that the one that powers the heating coil in the switch? 
Appreciate the 'simplicity' 😂 I'm just quite new to the world of wires, switches and relays. 
Ben 

Green White to ground is through the 'switch" when cold you should get continuity. If you put it in hot water you should get no continuity. You can do all that with it out the car (no power required). If you put a meter on the other connector to ground you should get some resistance as you will be measuring the heater coil.

mark1gls said

Connect up the thermo time switch and see how the car starts when cold and hot.
If no difference leave it connected.

If it's lumpy when starting then to much fuel getting into the engine but that could also be from old leaking fuel injectors.

Just connected it up and tried to cold start… just kept turning over no start. Then removed and started but got stuttery (which it never usually does when cold). Weird. Maybe the injector is damaged and just spraying too much fuel even when cold. 

Next try and unplug the 5th injector, there's a blue electrical connector on the 5th injector, unplug it.

Plug the thermo time switch back in and see what happens….

well mark1gls now I'm confused - so the image below is the connector that's been loose. I thought this was the TTS connector. But it sounds like you might have been referring to a different one previously and describing this one as the connector on the 5th injector?

The bigger switch on the engine block with the black&red + green/white (which you might have been referring to previously?) I haven't touched this far… 



 

That's the 5th injector electrical connector in your hand.

For reference the thermo time switch is fitted to the big flange coming out of the front of the head between cylinder 3 and 4  carrying the coolant to the top of the radiator and I think it's got a brown connector similar to the one in your hand.

I ran for about a year with the 5th injector unplugged as my fuel injectors were old and leaked fuel when switched off so the engine would be flooded when starting and took some starting then ran lumpy for the 1st few mins till the extra fuel got burnt off.

If the engine was left for about a week it would start up no problem but if used daily it would play up.


2 options

1 leave it how it is for the time being but keep up regular oil changes as it can contaminate the oil with petrol.

2. Pull the fuel injectors out (which can be tricky) and test them to see if they leak when the fuel is meant to stop, if they leak fit new injectors.


I've found my injectors last about 100,000 miles before giving trouble so I'm now on my 3rd set…  

Right, thanks for clarifying. What I'm still unclear on is what the impact of this connector being loose is? What does it do? 

Edit: car's done 85k miles.

blue plug excites 5th injector on cold start

So it's fed by the TTS and ergo having it unplugged has the same effect as unplugging the TTS connector on the engine block?

Yes that's correct