Exhaust analyzer

Sounds like it will be a challenge to get optimum mixture across all load ranges.

A number of Djet owners (and some K-jet owners) have gone to Megasquirt. With that you can map your mixture however you wish and at same time eliminate all the expensive Djet parts. There are probably other aftermarket replacement ECUs that are even better (but more expensive) www.peachparts.com/shopforum/vintage-mer...runs-megasquirt.html

But not racing, I am happy with Djet especially with full time AFR (or Lamda) read out and manually adjusting the ECU and MPS.

At present, I have noticed my AFR gauge reading higher than it did before. In other words, engine is running leaner. Fuel pressure is still same. Injectors may need cleaning, but perhaps something else could cause lean running?

Hi Graham,

lean in that respect means more oxygen. I would check ignition dwell and timing before I do anything else. Secondly an injector spray that is imperfect or too low could cause less combustion and more oxygen.

I don't have points. Converted to Pertronix 1885 several years ago. So no dwell to adjust

Timing also should not have changed. But it could be that centrifugal advance might be sticking (it did once before and I had to free up weights). That would give me less advance at higher speed/load. I will check timing! I may also have an air leak, so will check vacuum as well.

Along with the lean mixture, I also notice reduced power. But only when engine is really warmed up and has been on a long run. At normal temperatures, car is still quite lively.

Hi Graham,

actually I do not believe in a need for Pertronix on MB's D-Jetronic cars. They are (with few exceptions on early 250CE) always equipped with transistor ignition. That is why contacts do not have any current load and will not burn down as in other cars without transitor ignition. Using Pertronic with tranistor ignition module of Mercedes-Benz will just use double transitor switching. So even n original cars dwell will not change. Main failure will be coating on contacts due to low current or oil and fat. So I just wanted to point it out as a possible source.

And yes you are correct to verify everything else before you go to D-Jetronic components. A leak onn MAP sensor woulld create a richer mixture. That's why I did not mention this as a possible problem.

It is true that Djet points will not burn out because they operate at low voltage. But the fibre rubbing blocks still wear and therefore the points gap (and dwell) changes over time. Pertronix module completely eliminates this at a very low cost.

Pertronix also eliminates any effect of distributor bearing wear and shaft wobble.

There is really no negative to having double transistor modules. But a positive is that the Pertronix can completely replace the expensive MB module, if it fails. Just a few simple wiring changes required. Many owners have done that and at same time installed the Pertronix Flame Thrower coil (with apparently improved performance). I have not gone that far yet, but have the coil ready!

So as you can see, I am quite a believer in the benefits Pertronix can offer I just wish there was a similar replacement for the trigger points!

Hi Graham,

I also believe in Pertronix and will install it in my fin tail convertible. It does not harm to do it in transistor ignitions too. I just wanted to point it that there are little benefits. And yes I wish there was a solution for the trigger points as well. Jaguar / Lucas did that. But people were not too lucky with Lucas's quality of that solution either. So far I could not get hold of a Jaguar trigger point, neither the reed relais version nor the hall sensor version. I could only acquire an ECU and will analyze how they have interfaced those sensors.