Duty Cycle Pickup Lead

[pasogrande]

Next to my Bosch distributor there is a blue wire with the end wrapped in electrical tape.

The manual for the US Spec 280i S2 indicates (I think) it is the duty cycle pickup lead. Does it have a purpose? Maybe a predecessor to the OBD2 sensor?

Wilf.

[V8 Fettler]

Is there a photo?

[adam quantrill]

Oi! that's a V6, not a V8! ;^)

Sounds to me like a lead to connect an oscilloscope or dwell meter to check the dwell, sufficient being needed for the ignition coil primary.

[pasogrande]

V8,

It is the vertical blueish wire maybe two inches in front of the coil.




This pic is not much better. The other end of the wire is through the firewall to the ECU.



Wilf.

[mrzigazaga]

Hi mate...That looks a bit like the ballast resistor wire that i had on Delilah...Might not be though as I'm not sure about the different components on the US cars...Ziga

[pasogrande]

Mark,

On mine the blue ballast wire ends are on the other side of the engine, near that exhaust manifold. Yes, it may be for the US spec cars only.

Wilf.

[mrzigazaga]

Hi Wilf...Whoops sorry yeah of course the resistor wire is that side as well for the UK cars...What is the terminal on the coil that has no wire attached to it?..Probably nothing...Ziga

[pasogrande]

Mark,

I still have problems getting 12 volts to the coil, despite the new yellow and green wires I used to replace the bad old ones. I cheat by running a wire direct from the battery to that empty connector on the coil. One more thing to sort!

Wilf.

[mrzigazaga]

Mmmm...I was going suggest me sending you the schematics from the Wedge manual...(Bible) to see if there is a wire there that is the same..But you seem to have the area covered...Hopefully someone will know what it is who has a US spec car..Unless its from an old alarm as is the case with a lot of these un-connected wires...There were a couple of blue wires on Delilah that spring to mind..Actually one was completely blue and the other was blue with a white stripe suggesting it was a switching wire...If i remember correctly then the solid blue was from the ignition switch and it went to the solenoid on the starter...We had to replace that with a feed from the battery as it went into the relay board and was then linked to about 5 other relays..Which was causing problems.. before exiting out the bulkhead...

The blue/white was the flash control for the headlights, that was connected to the stalk switch and then ran down by the battery..(Same side as your coil) to the multitude of wires leading to the O/S headlight...Yours is probably neither of these but i thought it might be worth mentioning...Hope you sort it mate...Cheers...Ziga

[V8 Fettler]

pasogrande said:

V8,

It is the vertical blueish wire maybe two inches in front of the coil.




This pic is not much better. The other end of the wire is through the firewall to the ECU.



Wilf.

I didn't know the 2.8i had an ECU! Is it not mechanical fuel injection?

[RCK974X]

Misnamed I think - it's not an ECU but an ignition amplifier/trigger for the contactless ignition......

Although - some of the later 'K' series DID have a very basic ECU, an electronic control box to adjust fuel pressure via an EGO pickup to get low emissions. This was fitted to Audi and VW cars at least, not sure about others.

[pasogrande]

Below are two scans from the TVR manual.

The first is parts of two pages, one showing the Lambda Electronic Control Unit (sometimes called an Electronic Control Module); the other a picture of the coil with the duty cycle pickup wire.

The ECU is a similar size to the Electronic Amplifier Module. The main purpose of the ECU is to get information from the oxygen sensor to control emissions (I guess a condom wouldn't work for that!)



The second scan is part of the wiring diagram showing the lead connected to the last terminal.



I have no idea if the lead serves a useful purpose.

Wilf.

[RCK974X]

That page is really interesting....I've not seen that before.
The electronic unit I have seen (VW & Audi) looks very different, but does the same job as that description.
The metering units to match had an extra piece on the side, which was the actual control valve for fuel pressure.
The VW ones were known as Bosch 'KE' Jetronic to signify the extra electronics.

More than that, I don't know. Never worked on the KE, just know that it exists.

[mrzigazaga]

I heard of the KE-Jetronic also...Judging by the photo that wire is not connected to anything anyway...Unless its some kind of oxygen/Temperature sensor..I know most things like that are manifold or exhaust based but you never know..Generally if i find un-connected wires i extend the wire in all directions to see what is near it and if that has a connection missing..If its taped up then perhaps its not in use?...If its going into the ECU then maybe its just a dead wire?..Like when TVR cut out parts of looms.....

[RCK974X]

I reckon ALL cars are like that - even the old Fords (Granny, Cortina, etc) had extra unused plugs around, for stuff like central locking, electric mirrors, etc. That's before many years of different owners adding & removing stereos, alarms, and God knows what else.

For example, our old Volvo has a whole set of unused plugs - THREE behind each headlamp, which made me say "WTF??" only to find out that one is for the electrically adjustable headlamps, one is for high power headlamp wash wipe, and other is for spotlights/drivelights - all optional and/or on 'luxury' versions. They are just hanging there....

The only option really is to trace the wire and see if it's still connected or not, and then try to find out what it should do....not always easy, especially on a wedge !!

---

And not just cars... a memorable occasion at a friend's just purchased house, moving in all his stuff.
Him: "What's this wire ?"..... Me: "Careful, it might still be live"
Him: "Nah, don't be stupid, its...<ZAP> ...AAAH!...Oh F**K !! that hurt"

Luckily he let go.....and no heart attack. But it makes you think the next time...

[pasogrande]

Thanks for all the comments. I believe the wire is there to be used for some test, or maybe for tuning. Judging from the picture it left the factory unconnected, with electrical tape wrapped around the end.

I wonder if this is the explanation:

https://learn.sparkfun.com/tutorials/pulse-width-m...

We made an LED dimmer using pulse width modulation. Maybe the lead could be used to measure how the duration of the spark.

Wilf.

[V8 Fettler]

Interesting! The natural home for that floating wire does visually appear to be the coil LV terminal (unused crimp), particularly in view of workaround you are using. Probably need more info before re-connecting though, don't want a fire!

Is there any voltage appearing on the floating wire? Wiring diagram for similar?

Edit: KE-Jetronic info here: http://www.berlinasportivo.com/Technical/lancia/Th...

Edited by V8 Fettler on Saturday 24th January 07:41

[pasogrande]

BINGO!!! I've found the answer to my own question - although I don't fully understand it.

Below are scans of two pages from the Emissions section of the manual:

The first explains duty cycle.



The second explains the system, pulse ratios, and using a dwell meter



So that wire just sits there ready for somebody with the right test equipment (and skills)

(And V8, that unused crimp is mine; it is where I connect the +ve terminal of the coil to the battery)

[pasogrande]

V8,

I just spent a few minutes looking at the Berlina Sportive website you referenced. Very interesting.

It looks like an updated version of what I have. I didn't see any mention of the duty cycle pickup lead, but it is an excellent source of information on many other things.

Thanks for sharing it,

Wilf.

[adam quantrill]

From your manual it appears that you need a lambda-sensor type ECU for it to be of much use. Although it will tell you if you're obviously overfuelling if there's a fault - you will see the dwell shoot up.