CIS-E 1.8 16v Thermo Time Switch Wiring??

[HeyMayneItsB]

A PO had done the 1.8 16v engine swap in my Rabbit, but did a half-ass job, so I replaced the entire harness with a (supposedly) untouched PL 16v Scirocco one. However, there was no connector from the ECU for the thermo time switch

The PO had some round-a-bout loop from the harness to cold start injector, with one wire going to the thermo time switch and the thermo's other wire being looped around to the starter motor. But the cold start injector never worked with that setup, and I was having starter motor issues. How is the thermo time switch supposed to be wired? Isn't there supposed to be a brown connector coming from the ECU through the main engine harness?

Unrelated, but I'm also missing one of the two O2 connectors on the harness, leading me to wonder if either the harness is not from the engine it was claimed to be from or it had actually been cut up...

[HeyMayneItsB]

Bueller...

[ps2375]

Have you looked in the wiring diagrams in a Bently Manual?

[HeyMayneItsB]

Have you looked in the wiring diagrams in a Bently Manual?

Yep, and I have yet to decipher them I like pictures

I have both the Mk1 and Mk2 Bentleys, and I've searched using several key words on the forums for both threads and posts, and all I know is that the thermo time switch controls the cold-start valve and, from what I've heard, it's supposed to have a connector for it to the ECU on the engine harness. But mine does not.

[ps2375]

I don't know what to say.

[20v_boost]

The thermo-time switch does not connect to the "ECU". I'll have to look at my bently when I get home but I'm sure its a stand-alone kind of circuit.

Basically when the thermo-time switch is cold, it fires the cold-start injector. It receives heat from 2 sources, heat from the cylinder head, or heat from an electrical current that passes through it while you're cranking. So if the engine is warm, it doesn't fire the cold start injector. If you are cranking for a while, it stops firing so you don't flood your engine.

-Alex

[Madvwz]

Could there be a fuel enrichment module connected (possibly home made) that is throwing you off?

Edit: Rather, an attempt at a fem?

[HeyMayneItsB]

The thermo-time switch does not connect to the "ECU". I'll have to look at my bently when I get home but I'm sure its a stand-alone kind of circuit.

Basically when the thermo-time switch is cold, it fires the cold-start injector. It receives heat from 2 sources, heat from the cylinder head, or heat from an electrical current that passes through it while you're cranking. So if the engine is warm, it doesn't fire the cold start injector. If you are cranking for a while, it stops firing so you don't flood your engine.

-Alex

Well then the PO may have been on the right track, but a "close but no cigar" type deal because it was all kinds of ghetto and not working anyway.

Could there be a fuel enrichment module connected (possibly home made) that is throwing you off?

Edit: Rather, an attempt at a fem?

Nope, and I threw the old hacked up harness in a box (in case I need some OEM connectors or wiring later) and installed an entirely new harness, repairing every broken or ghetto wire connection in the bay in the process. The thermo time switch is the only thing not right (currently just not connected at all), as well as the mysterious lack of an O2 connector... (only the spade connector is present).

[20v_boost]

There's a whole section in the scirocco bently about the thermo-time switch and how it works. But anyway, as you know there are two pins, one switches the cold start injector to ground, the other is the internal heater. Obviously the injector hooks up to the switched pin. You can tell which is which by measuring the resistance to ground (body of thermo-time switch). One pin will be close to zero ohms when the thermo time switch is cold, and open circuit when it's hot enough to switch. The other pin will measure the resistance of the internal heater.

The other pin of the cold start injector hooks up to the fuse block and to a source that has +12v during cranking only.

I'd read the section on the thermo-time switch, stare at the wiring diagram, read the section, stare at the diagram, etc. until it makes sense. That's what I did.

Cars that have an ECU don't need a thermo-time switch or even a cold start injector for that matter. They can just command the main injectors to squirt more fuel during cranking.

-Alex

[ps2375]

Cars that have an ECU don't need a thermo-time switch or even a cold start injector for that matter. They can just command the main injectors to squirt more fuel during cranking.

Not totally true of the CIS-e cars, as they have both an ECU and the cold start injector along with the aforementioned thermo-time switch.

[HeyMayneItsB]

There's a whole section in the scirocco bently about the thermo-time switch and how it works. But anyway, as you know there are two pins, one switches the cold start injector to ground, the other is the internal heater. Obviously the injector hooks up to the switched pin. You can tell which is which by measuring the resistance to ground (body of thermo-time switch). One pin will be close to zero ohms when the thermo time switch is cold, and open circuit when it's hot enough to switch. The other pin will measure the resistance of the internal heater.

The other pin of the cold start injector hooks up to the fuse block and to a source that has +12v during cranking only.

I'd read the section on the thermo-time switch, stare at the wiring diagram, read the section, stare at the diagram, etc. until it makes sense. That's what I did.

Cars that have an ECU don't need a thermo-time switch or even a cold start injector for that matter. They can just command the main injectors to squirt more fuel during cranking.

-Alex

Everything I recall reading about it in the Bentley has only described what the thermo-time switch does and how to test if it's functioning, and at some point simply says "check the wiring" but does not go into how it's supposed to be wired. And as for the wiring diagrams, I can't seem to decipher any of those alien drawings...

And that's not true, at least not for CIS-E Jetronic. I know that CIS-E Motronic does not use a thermo-time switch at all, yet I believe it still uses a cold start injector (the Motronic ECU just controls it instead of the thermo-time switch on Jetronic). I'm running Jetronic, however, where both are needed for the engine to start properly (sometimes not wanting to start at all, particularly when it's cold outside).

[Madvwz]

Any updates?

[HeyMayneItsB]

Any updates?

None that I'm aware of at least

[Madvwz]

Well, I looked briefly at mine and I think it's a blue w/yellow stripe wire and a ground...i'll try to trace it back tomorrow and get a pic.

[HeyMayneItsB]

Well, I looked briefly at mine and I think it's a blue w/yellow stripe wire and a ground...i'll try to trace it back tomorrow and get a pic.

Thanks! I'm wondering if perhaps the PO was on the right track with the way they had it wired, although a tad ghetto (and about 3ft of extra wire), but the ignition wasn't wired properly in the first place so splicing into the so-called ignition wire that they had caused the thermo-time switch (and thus, the cold start injector) to not work.

[Madvwz]

Seems the tts and cts have a green/white wire that connect the two on one pin and the other is a black/red that goes up to the ign. switch.

[HeyMayneItsB]

Seems the tts and cts have a green/white wire that connect the two on one pin and the other is a black/red that goes up to the ign. switch.

So it is looped around like it was originally wired... except originally done half-ass and didn't work.

Just to make sure I have it right: ECU connector to the cold start injector, green/white wire to thermo-time switch connector, black/red wire then splices into the ignition wire? Which of those wires are positive/ground? In case mine aren't the same color...

Thanks so much for finally putting this to rest!
~B.

[Madvwz]

So it is looped around like it was originally wired... except originally done half-ass and didn't work.

Just to make sure I have it right: ECU connector to the cold start injector, green/white wire to thermo-time switch connector, black/red wire then splices into the ignition wire? Which of those wires are positive/ground? In case mine aren't the same color...

Thanks so much for finally putting this to rest!
~B.

There is a thinner (maybe 14-16ga.) black/red that comes from both the csv and tts that merge into a thicker black/red (maybe 12-10ga.) that go to the plug on the ign. switch here -

Now this is on my 86 8v GTI (former winter beater, mostly in pieces) and in pulling looming off of that harness, I did find a splice that connects as I stated before, so this may be an easy solution in your case.

[HeyMayneItsB]

Wait, so then both wires on the CSV and TTS are connected to each other? I thought I had everything straight, until you said that the green/white wires connect each connector pin, and the red/black wires on each connector merge together at the ignition. Which color wire(s) goes from the ECU to CSV through the engine harness?

[Madvwz]

Wait, so then both wires on the CSV and TTS are connected to each other? I thought I had everything straight, until you said that the green/white wires connect each connector pin, and the red/black wires on each connector merge together at the ignition. Which color wire(s) goes from the ECU to CSV through the engine harness?

No wires to the ECU in this case. Not sure why this one was spliced, but it always worked. I just found out where it was spliced tonight.
I'm assuming that the position on the ign. switch plug was as 20v_boost stated 12v during cranking only. If the car was warm, the tts would be 'open' and not accuate the csv.
Make sense?

[Madvwz]

Obviously, 14 = tts and 13 = csv.

[HeyMayneItsB]

Hmmm... my 16v harness has a connector from the ECU to the cold start injector though

[HeyMayneItsB]

I FINALLY figured out that the connector from my ECU that I thought (according to every diagram I had found) was for my cold start valve is actually the other connector for the heated 3-wire O2 sensor

So now I've gotta get the cold start and thermo-time switch wired. From what I've gathered one pin on each connector are connected to each other, and the other pin of each is connected to the black/red wire on the ignition switch. What function is that wire? That's not the starter motor wire is it?

[Glegor]

Not totally true of the CIS-e cars, as they have both an ECU and the cold start injector along with the aforementioned thermo-time switch.

look at the older EFI vehicles?

all my older toyotas, and my current 89 4runner have all had EFI (real efi, better than digifant) as well as a cold start injector..

but yes, the thermo-time switch gets its signal from the starter, then the thermo-time switch sends power to the cold start injector until you let off the key, or the switch gets hot enough to shut off the injector..

[HeyMayneItsB]

Alrighty, thanks!

Now to figure out my lack of cold-running/warm-up enrichment... but that will have to be another day, no time before SoWo.