Euro coil/ballast resistor/starter bypass box (Tom Jones)

[BillWilliams]

Pat, In taking the car apart, I did not see it at all and I can not pick it up on the EURO wiring schematic.

[Jeffrey Kok]

Guys we don't have that stuff over here, just normal wires.

I don't know why you have, might it be because of emissions, or your low octane rate, we had 98 in those days. maybe things got hotter because of the different settings?

[PatAllen]

Pat, In taking the car apart, I did not see it at all and I can not pick it up on the EURO wiring schematic.

you know it is hiden and snakes in the harness that runs over the firewall...

just a thought...

[BillWilliams]

I had that harness completely apart but it is a good thought,

WHat does it connect to?

[BillWilliams]

Jeffrey, any chance you can post some photos of your engine bay? Especially the coil area?

[PatAllen]

I had that harness completely apart but it is a good thought,

WHat does it connect to?

see it just as the wire itself that powers-up the coil from the ignition key, normaly there is a piece that has clear insulator, like cheap speaker wire. There is even a yellow label on some with the resistor value on it.

i realy dont know if it apply to euro or tourings, but it worth a check.

Also another method to see if you have one is to monitor the voltage at the coil B+ when the car runs. If its steady batt voltage (±13.4v)then there is no in-line resistor, thus the coil must have one.

If it falls near 10v then there is a hidden resistive wire somewhere...

[MikeinNC]

My touring was delivered to the Netherlands so I guess it would be considered a Euro, and a Type 74 like Jeffrey's. It was restored over there and came here about 4 years ago. Wiring harness appears to be intact and un-molested(original connectors) but you never know eh? The coil power (green wire) runs straight to the coil location with out interuption. (No resistor wire in series either, 12 volts). No evidence of a balast resistor ever being mounted any where near the coil. Looks just like the euro touring wiring diagram in every respect. Cannot help with the original coil type however as I put in a blue when I redid all the mechanicals.

From my knowledge of the wiring diagrams, especially for the US cars, including 74Tiis, the resistor wire, when installed, shows as a separate item and is clearly marked.

I have my theories on why the US cars have that but I have no basis for this and I don't want to get flamed Besides there are folks much more knowledgable than I on such minutiae.

A good source would be to check with Martin as his is a very near original Tii touring

HTH

[jgerock]

Just thinking out loud:

I think the U.S.A bound cars had to deal with emissions-related equipment which made the engines hard(er) to start, so BMW added the starter relay circuit which bypasses the resistor during cranking so that full coil voltage was available to the distributor.

Euro-spec cars didn't have the emissions-related equipment, so they didn't have to incorporate the relay.

[BillWilliams]

Thanks Mike. That makes the same set up as I have

Jim, i think the ballast resistor knocks down the power - it does not increase it.

The bypass just allows "full power" (whatever that is) at start up only then allows a reduced "power" after start up. So I am not sure why US cars would need less electrical "power" while running than Euro cars.

I feel so foolish calling stuff "power" but that is all I know, it must be amps volts or something like that.....

[JohnS]

I'm sure that this is all old hat to you guys, but thought I'd add a link to Zenon's FAQ on the subject:

http://www.bmw2002faq.com/content/view/69/32/

[PatAllen]

the resistor bypass has nothing to do with emissions themselves.

the bypass is done to compensate for voltage drop when the car is started. Battery voltage could fall as low as 8volt when it cranks, under cold temp so the coil is firing less at this moment without the bypass, which is exactly where it needs more spark to start the motor.

The coil is designed to work at 10v primary voltage all the time.

BMW was not alone to do this. IIRC my 1983 ford Escort with its Thick Film Integrated (TFI) ignition module has a crank sens to bypass the plastic resistor to the coil. Theses where failing often, leaving a car that was running only when it was cranked...lol...

Maybe it has something to do with colder climates only ?!?

[BillWilliams]

John, Zenon's FAQ is helpful and insightful

[BillWilliams]

Well, the "new" black coils are not black. They are silver like the "new" red ones. Time to paint.