Tried this on the SL page but got no response so I will try it here.

I searched this issue a bit and found nothing, but I'm sure I saw it somewhere on this site, but then again, maybe not.

On the early D-Jet V8s that have electronic ignition controlled by points, do the points do anything more than trigger the transistor ignition box? Are they tied in with the function of the FI computer? I know there are trigger points for the FI in the distributor, down in the guts of the distributor below the breaker plate. But do the ignition points or transistor box send any critical signals to the FI computer?

Reason for the question is...if the ignition box fails you are usually screwed until you get a new one. I'm wondering, can the system be re-wired to operate like the old style breaker ignition systems? Seems like this should be fairly simple, unless there is some not so obvious linkage between the electronic ignition box wiring and the FI computer. If a person had an SL or other model that is seldom used (I have) it seems a lot cheaper to replace a $5 point set every year or two rather than to be stranded on the road by a $400 ignition box. One tow truck bill will pay for a lot of point sets, not to mention the cost of the ignition box.

Just a thought...any advice would be greatly appreciated.

230/8

It is possible to bypass the box, the points are not connected to the EFI box at all as far as I'm aware (99% sure), only the EFI trigger points are. If your box is working fine, there's no need to replace it. If you're paranoid, carry a spare condenser/wire in your trunk so you can change it in 15 mins or so should anything happen to the box. Or, better yet, get a petronix or crane setup, bypassing the points AND box.

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1972 280SE 4.5
2014 Jeep Grand Cherokee Limited "Hefe", 1992 Jeep Cherokee Laredo "Jeepy", 2006 Charger R/T "Hemi"
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Correct me if I am wrong, but when I replaced my points with the Crain Fireball, the Crain unit eliminated the need for the oem box. Which would lead me to beleive that there is no direct connection to the FI computer past the points and the box. I guess what I am trying to say if you replace your points with a Crain unit, you would never need that $400 iginition box. I hope I've got it right.

Thanks for the feedback. I was not aware that the Pertronix replaced the ignition box on the V8s. I have used them on my Mustangs, very good stuff, but was unable to get one to work on my 230/8. There are so many variations of Bosch distributors that the Pertronix factory boys just could not get a proper parts set to work in my model. And I did not want to send in the distributor for them to experiment on it. I may give Pertronix a go for my SL, but may also just keep an alternate wiring diagram in the glove box along with some fresh points and condensor.

By the way, my distributor has a condensor inside it, just like the old-timey set-ups, which is why I asked the question. Instead of current running through the coil to ground in the distributor, on-off with the points opening and closing, my set-up grounds at the coil with the box apparantly sending a jolt through the coil in response to the trigger signal from the points. I did not notice a conventional style ground wire inside the distributor, which I think would be needed to make the regular old-style system work properly. But maybe I missed it...

At least that how I think it works.

Thanks again,

230/8

i am wired around the cd box in my 130 engine and it works just fine...
you can wire the crane with the cd box if you want to.. you'll get more spark but it's not really necessary...

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72 W114/M130

RedMeat cartoon

The v8 EFI distributors (and the 280E/250E distributors) have TWO sets of points. The conventional points are for the ignition. Lower down in the distributor is a second set of points for the EFI system. If you're worried about ignition, especially on a 230/8, the EFI points have nothing to do with it.

Having said that, you have a few options for benz ignition systems.

The 230/8 came with the conventional black coil, .9 ohm balast (gold metal band), a condenser and conventional points. Each of those items requires the others.

The M115 engine had a different set of parts to form a conventional ignition system. A red coil and red band on the balast makes these parts stand out.

The 250/8 and most of the 13 or so 280 varients had a transistor control unit wired into the circuit. There were at least 4 varients of the control unit used between 1968 and 1975. The wiring pattern chosen for the system is dictated by which box you have. The parts were pretty much the same, notably two balasts, one .4 and the other .6 ohms (silver and blue bands; though at the moment I forget which one is which). There is NO condenser in the system. A capacitor is present for radio noise suppression, but that's different. Also, the coil is blue to indicate it's special purpose.

In the non-factory cases, there are systems from cranes, petronix and a few others. None of which I have experience with, but there are plenty of great stories (and several bad experiences) here and elsewhere on the web to follow.

You can convert your car to any of the above systems, just keep the parts catagorized as above. I have a "portable" ignition system I wire into any parts car I run across to see if it's "alive". It nicely bypasses all of the car's wiring going from the distributor to the battery.

Spare ignition boxes are always available on ebay. I have at least 5 kicking about. They make good presents when I visit somebody or ask a favor of a fellow benz fan.

-CTH

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