W116 D-jetronic trigger points

[Hugin]

Hi

Have a -73 280SE that is running rough.
Have replaced rotor, dist cap, coil, all wires, plugs (BP6ES 0.6 mm gap).
Installed Pertronix point-less ignition.

During the process, I discovered that cyl #1,3 and 5 plugs are black and cyl 2,4 and 6 are clean. Took out points and cleaned carefully, problem remains the same.

Replace trigger points?

I feel this is connected to the triggerpoints somehow.

Any thoughts?

Tom

[Frank Reiner]

H:

The D-Jet ECU contains a logic circuit that specifically tests for spurious pulses from the trigger points, and alternates the logic pulses that drive the output stages so as to drive one set of injection valves at a time (two sets of three valves each). As a consequence, it is quite unlikely that the trigger points themselves are the culprit.
The greater likelihood is that there is a fault in the logic circuitry that is causing extra pulses to be supplied to one of the output stages.

[Graham]

Originally Posted by Frank Reiner

H:

The D-Jet ECU contains a logic circuit that specifically tests for spurious pulses from the trigger points

It does? Where did you find that information Frank?

On the V-8s, we have found that worn trigger points can cause what appears to be over-richness. Some Porsche owners figured it might be caused by worn points bouncing and sending multiple pulses to the ECU.

On my own car, I found a low mileage used set of triggers and they cured problem. It is possible to get more life out of the triggers by bending the tabs. Norbert (Nordfisch) who sometimes posts here has a simple tool that helps adjust the trigger points. Several of us have reset the points so that they stay closed for about 120-130deg. That seems to work on the V-8. Presumably same for I6?

PS: You can check the angle with an ohmeter and a home made gauge like this one:



This thread may be of use: http://www.peachparts.com/shopforum/vintage-mercedes/264678-testing-trigger-points.html

[Frank Reiner]

Originally Posted by Graham

It does? Where did you find that information Frank?

Graham, that tidbit came from a 1968 Electronics World article about the introduction of D-Jetronic on the VW Type 3. The article was written by:
Fred W. Holder / Technical Supervisor, Bendix Field Engineering Corp.
The patents that covered the D-Jet were obtained by Bosch from Bendix. The D-Jet ECU was a much improved version of the original ECU designed for the Bendix Electro-Jector. That original ECU contained vacuum tubes! First application was 1959-1960 (?) Chrysler B-block engines. Eventually all were recalled and converted to carburetors.

[cth350]

Never saw that adjustment tool before, but I remember the thread being started way back when.

I just dropped Norbert a line to see if he is still making that tool. I saw mention of two out of three dimensions. The overall diameter he says. The three different notch widths get mentioned, but what is the depth of the notch?

For me, it's academic curiosity, since I haven't owned a D-jet car for ten years, but I'd happily get another.

-CTH