Looking for Djet distributor upgrade options.

[Atlas-Auto]

Hello everyone. This is my first post here. Hoping I can find some help with a '75 450SL I have in the shop. I was able to determine the ignition control module harness was bad so I repaired it. That then lead me to find that the ignition control module itself is also bad and not supplying the ignition coil ground.

The customer barely drives this thing but wants it to start and run reliably. Specially come October for a local car event called Cruisin the Coast.

In researching my repair options, I came across an old post made by Deltacom that has really peaked my interest in what appears to be described as an electronic distributor conversion for pretty much the exact car I have in my shop. Unfortunately Deltacom's last activity is almost 10 years ago and I can't seem to find much additional information on the subject beyond this post.

Originally Posted by Deltacom

Replace distributor with an electronic one.
Replace ignition control unit and coil with the ones in the pictures.
Remove or bridge ballast resistors

Originally Posted by Deltacom

Hello Peter. Thank you for your contribution to RadioTek’s query. Basically you are correct in that the D-jet injection timing are built within the existing distributor. However, if the conversion would include electronic distributor, coil, control unit (switching unit) and eradication of voltage fluctuation induced by ballast resistors then there are no technical requirement any longer to retain old distributors as the function of the triggering points is to supply the old-type switching unit with engine speed. They provide signals which determine when and to which cylinder fuel is to be injected. The contacts also supply information concerning engine speed to determine the amount of fuel that needs to be injected into the engine. which would of course be provided by the coax on the electronic distributor to the new switching unit. All these functions are effectively taken over by the new switching unit (electronic control system).

As you know, the Bosch D-Jetronic electronic fuel injection system is composed of 3 major subsystems: the air intake system, the fuel system, and the electronic control system. The D-Jetronic system uses constant fuel pressure and flow, so that only injection duration needs to be modified to control air/fuel mixture. The D-Jetronic system measures incoming airflow by monitoring intake manifold pressure. Engine speed, temperature, and other factors are monitored for the purpose of fine-tuning injection duration. Needless to say RadioTek would need to avail himself of the 4-point connecting plug to the new switching unit wired to the connection block where the flex of the old type control unit was wired to.

I carried out this conversion on my 450 with substantial improvements results and has been working well for the last 6 years.

In answer to your questions, the control unit in the picture is the replacement of the old type in the W126 500 and the coil is used in the W124 4.2 and 5.0. It also fits other models.

There are several advantages in the choice of these components, not least is the cost of these units for something like a 1/10 of the original parts costs.

With best regards

If anyone has additional information on what Deltacom is describing here, please do share. If this an actual option for a conversion to completely move away from the points systems, then I would like to follow that route.

Thank you for your time.

[TZ_280SEL]

I replaced my control module with a Pertronix unit. It performed very well until I decided to switch everything to megasquirt about 6 years ago.

[cth350]

The ignition module's case must be well grounded to the chassis. That is often overlooked.

I used to know a very sharp fellow that like the early 80s ignition system grafted to the 60s / 70s cars. But to do that for a d-jet car means also replacing the EFI because of the 2nd set of points in the distributor.

mega squirt and similar conversions abound. But just using the right parts (or at least, not 3rd hand used ones) is usually sufficient. There are write ups here and elsewhere about how to rebuild the EFI points and their rubbing block.

-CTH

[Graham]

Have a look at Benzworld and in particular this thread:
https://www.benzworld.org/threads/pertronix-install-with-and-without-switchgear.1714668/

If ignition module is bad, then you will need to bypass it and install a Flamethrower coil as described. Also add a resistor to get tach to work properly. All described in that link.

I have had one of these installed for a long time - maybe 16 years!