Can someone explain the purpose of the distributor green wire?

[alabbasi]

My 72 280CE stopped running and does not appear to get any spark. Coil is new so I'm thinking it's the green wire or the ICU.

How does this all work?

[Frank Reiner]

The green lead from the distributor is a coaxial cable, carrying the signal from the points or pickup coil to the ICU.

[Mike D]

and yes, any decent quality A.V. coaxial cable will suffice for a replacement.

[alabbasi]

Mike, really? How so?

[Mike D]

It's just a switching wire. The spark is actually generated by the transistor box. It just shows "open-closed" and the transistors in the ECU send the signal to the coil, no real current involved in the wire.

I think I have a Hot Spark replacement for the 6 cylinder laying about someplace. If I can dig it up you want it? Postage cost only.

Congrats on selling the 300D but bummer, 'cause now I gotta source those parts from somewhere else.

[alabbasi]

I was thinking about buying a petronix setup. I'm assuming that this will work?

[Mike D]

Pertronix, Hot Spark pretty much the same. The Hot Spark guys are making the early version of the Pertonix system under license.

The newer version of Pertronix is a lot more refined. Hot Spark is a simple Hall Effect switching magnet.

[alabbasi]

Mike, thanks. I need to figure out what I have first as the 280CE distributor is not the same as the earlier cars. Mine appears to have an arm that pivots to the right and has a one piece point setup.

Also, when I bought the car, the green wire was cut so I used a regular wire and bullet connectors to connect it to the ICE. This has worked until now so I'm not sure what the COAX dial is about.

Also, when I put a test light connected to the +ve terminal on battery to the points, it would light up regardless of whether the points were open or closed, provided that the green wire was connected to the ICU. Only when I disconnect the green wire from the ICE, the system would only ground when the points were closed.

Does this sound like correct behavior?

[Mike D]

The coaxial cable was simply a more efficient and durable wire.

Nothing fancy about it until they went to electronic ignition and then the shielded capabilities came into play. The "newer" electronic ignition set up was a Variable Reluctor system which is essentially just a generator. It used the braided outside cable as a shield to get a cleaner signal.

Yeah, the test light lighting up sounds about right. Remember, the original set of points were merely a "switch" (think of them as a floating ground/earth much in the same way the over heat fan sensor activates the fan when it closes and provides and earth to the fan relay) which triggers the transistor in the ICU. The spark is emitted by the box, NOT like the Kettering style points set-up most American and British manufacturers used which supplied the actual coil voltage.

[alabbasi]

In that case, it may then not be the green wire itself but the coil or the ICU?

[Mike D]

If you've got continuity at both ends of the green wire and the points' ground is good then it's not the wire causing the problem. What reading, if any, do you get with a dwell meter?

Inspect the points for burning or corrosion. Since they do not get as much voltage as the standard points system they are more susceptible to oil build-up or corrosion preventing them from making contact.

[meltedpanda]

look for a short AL, I chased this one time on a old 220 found that I was shorting out the distributor with a frayed wire ,IIRC

Had zero spark and could not figure why, simple fix for me

[sjefke]

Al, if you don't get a spark, go back to basics first. Pull distributior cap of and see whether points spark at all when you crank the engine. If you don't get a spark at points, your LT system needs checking.

If so, then put cap on and see whether coil HT lead gives spark. If you don't get a spark from the coil HT cable, then your point-coil system is messed up. If you do get a spark, check the rotor and distributor cap. You may have a bad carbon point in the cap or bad rotor.

I do agree that you need to chase shorts first. Check the wire that comes from/goes to the points. If that one has a short, nothing works.

Good luck,

Bert

[alabbasi]

Thanks guys, right now when I put power to the point, the test light lights up when the points are open unless green wire is disconnected so I'm guessing my rigged wire is working correctly. I'm now guessing that it's either the coil or the ICU. There is no spark from the points at all when the system is hot.

What's an LT system?

[meltedpanda]

I have a few ICU's lying about , what is the part number on yours?