K-Jet ECU – what does it actually do?

[LD50]

ok, so I was trying to figure some stuff out on the 16v/KR motor in the syncro, to do with fuelling etc when I realised I couldn’t pinpoint exactly what the ecu is supposed to control.

The fuelling seems to be adjusted mechanically by the metering head, extra fuel via the Warm-up-regulator, ignition seems to be fixed and comes off the cam (doesn’t look to have a vacuum adjust on the dizzy like 8v)…so what’s actually left for the ecu to control?

I don’t have the ISV in the mix on mine so perhaps that’s the magic ingredient but so far it seems to run ok without it. The mechanical bits are there but it’s not plugged in.

I tested with just blocking off the open end of the vacuum tube which goes to the ecu and the motor continued running as if nothing had happened. I haven’t tried actually unplugging the ecu to see if that makes any difference but only because I didn’t think of it till just now.

Anyone got any ideas?

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[Housey]

The ECU on the CIS/K-JET controls the ignitin timing and thats it. its using the internal MAP Sensor to adjust the timing. a bit more controlable then a vacuum advanced distributor.

the ISV has its own “ECU” a “relay” looking box with the numbers 244on it. and this controls the ISV and is activated with the idle swith on the throttlebody

the car will run when the vacuum disconnected on the ecu, but it won’t be any good as the timing will be static (more or less)

[LD50]

right that makes sense. I just couldn’t figure how it would vary the timing from the ecu. ok then I need to figure out whether that’s doing it’s job and if not why not. At the moment it doesn’t really sound different whether connected or not though I might need to check that in a bit more detail ..e.g. thru the rev ranges, or with the gas analyser (but it’s very slow)

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[LD50]

ah wait – that’ll need the loom for the ISV etc plugged back in too won’t it…

There was a white plug near the steering wheel which seemed to be where it should go but there was one black wire which was separate and cut which I don’t know what to do with.

I’m sure I saved a pic from the dismantling but I can’t find them :\

thanks for the info!

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[Housey]

could be usefull to have the ISV “relay” connected

i there is about 8 years since i last had anything to do with a K-Jet system. so i’m a bit rusty 🙂

[LD50]

is that the box on it’s own wiring loom which goes behind the centre console? or a different one?

The lone black wire was the thing which confused me. will take pics once I’m not ill anymore.

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[Housey]

it should be yes

[LD50]

right, ok – well I have that box/loom etc and found where to plug it in (well it was the only plug which matched, a white one near the steering column), but there was one stray black wire on the ISV loom which I had to cut (rather than unplugging) when removing it from my old 16v GTI.

I carefully took photos of the gti stripdown but for some reason I can’t find them now, so I don’t know if it’s just an earth (though would expect that to be brown) or some special signal wire or what. So far it’s made no difference plugging the ISV controller box/loom in or not so I suspect the black wire may be important. I actually have a spare ISV controller box and a couple of spare ISVs too so it should be possible to get it working..just as soon as I solve the mystery of the black wire. If it’s to do with timing then perhaps it could also be to do with the wires going to the distributor cap so will re-check everything there. So far I’ve just plugged things in where they looked like they should go (or fitted) and it fired up.

If anyone else has a working KR/16v and could take a look that would be super handy. I get “dog-head” when I look at the wiring diagrams in the haynes manual

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[LD50]

ok so these are the wires I have for the is controller….

I’ll need to double check but I found a matching socket for the biggest plug and think I found one for the second biggest but the single one and the stray cut black wire are a mystery to me unless I can find my gti disassembly pics…which so far I can’t.

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