Hi,
this forum was recommended to me... and this is really a great place for guys like me, interested in the D-Jetronic system.
We have a forum in Germany, German and English language "oldtimer.tips", too.
We are more conservative than you are, mostly just trying to find out everything about the system and how to repair the components. We are hobbyists mostly MB, but also BMW, VW, Opel, Porsche, Renault, Citroen, Lancia... all the car brands D-Jetronic was installed in.
I by myself designed a tool for re-adjusting the trigger points to the original values. Simple to be rebuilded if you have a lathe - I will send you a figure on request.

Now my own request:

Does anyone here own a Ditron 812D tester, too?

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I own such a device, but without any instruction.
It once came to Europe with the instruction, but it got lost.
I bought the Ditron some months ago on ebay from switzerland - the seller told me he had bought it many years ago at ebay USA.

It's no problem for me to understand and use the basic testing functions, but this tester is not only a testing - but an ECU-simulating device.

I don't really need the Ditron 812D to diagnose or optimize my car - I own some other testers.
But because the D-Jetronic-system is my hobby, I would like to understand the additional function, i.e. what the manufacturer intended the user to test / adjust with it.

Hope that someone still has the instruction for the tester...
My tester has serial #119 - don't know how many were built at all.

P.B. "Brad" Anders described the tester: D-Jetronic Testers as being similar to the Janbo Model 112 he described more detailed.

Does anyone own the tester / the instruction?

Please help...

Regards
Norbert

Brad Anders and Bowlsby are my two thoughts as far as reference is concerned. Both are members here. I think Brad is pbanders here and Bowlsby is Bowlsby. Try PM feature to reach them directly in case they don't see this.

Good luck...

Hi Norbert,

Brad Anders had that tester at one point, you might email him, he might still have it and the manual. I just have the EFI Associates 9100 (MPC) and 8100 (AFC) testers

Compliments on the VERY nice D-Jet website you have created, I will definitely spend more time on it.

I also build D-Jet (and L-Jet) FI wiring harnesses, and rebuild/recalibrate the MPS using new diaphragms available here in the USA. See my website in my signature below.

Hi Jeff,
thanks for your Wellcome...
I already noticed your website before and tried to contact you for harness parts that are NLA in Germany some months ago.
I don't do any workshop job at this time, just developed a tool for readjusting the trigger-points some years ago.
I then got more and more interested in the D-Jet-System I got trained on about 40 years ago but didn't really do the job since then - my own classic car (Opel Diplomat, equipped with D-Jetronic) I own for many, many years running fine and parts always being avaible when I needed them.
Volker "Dr.D-Jet" has created the oldtimer.tips website, I just participate from all his work. He just yesterday told me he actually does translating the older articles there into English language, too - a lot of work remaining to be done. I believe in he is working about 40 hours a day...

I will take your advice and try to contact Brad one more time - and publish some information about my "trigger-points-tool" here on the website. The tool is known in some Mercedes-Benz-forums but seems to be unknown to you.

Here at this time a picture showing the tool in position - you will understand, what it does.
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And another one showing the tool in a 914-trigger-points-set:
Click to view attachment

Regards
Norbert

Wow, I just checked it out. Another great D-Jet reference! With your site and the sites I already go to all the time (Bowlsby, Anders) I may actually figure out how this damn system works, particularly the MPS. I may yet have a promising career waiting for me as a D-Jet technician someday....

I need to learn more about your trigger points set tool. Trigger points are like the only thing I haven't replaced before. Is setting them correctly in place normally an issue?

Thanks for checking in Herr Nordfisch.

Hi,
it's absolutely no problem to replace the trigger-points-set because it is being adjusted not by the mounting-screws but by the sheet the points are mounted on.

Bosch said the trigger points are not adjustable at all- and people believed in this for about 45 years.
I had a trigger-points set I had misadjusted by myself many years ago, made some re-engineering and designed the tool I will introduce soon here in the forum. It has been well approved now on four continents...

Regards
Norbert

No one who owns the Ditron 812D tester?

Still looking for the instruction...



Norbert

Interesting site but no MPS adjusting info other than "don't touch".

It's not my site...

But you find any information there. Look at section 4.3.

You can't really tune a MPS. Just mistune it. The MPS is the very central device the ECU does get information from how much fuel to inject at the different load-conditions.

It has roughly the same meaning as the 'space cam' ('Raumnocken') in previous mechanical injection systems.

The D-Jetronic is a fully integrated system - depending on any single part operating within the motor-specific limits that are pre-defined by the factory-compiled individual setup.

Regards
Norbert

---------- What about the Ditron manual? --------

Norbert, I have spent a little time on that oldtimer website and while I virtually all that I see, I have one little nagging issue.

He refers to the MPS as a MAP sensor and it is not. Modern cars use a MAP sensor but the MPS is not a MAP sensor. Its been a long time since I read it and I do not own a copy any more, but I think it was the big blue Bosch book on fuel injection that describes the differences. Forgive me if I misstate the differences but this is what I recall:

Manifold Pressure Sensor = senses intake manifold pressure which is a value in relation to atmospheric pressure.

Manifold Absolute Pressure = would be an absolute pressure value value not related to atmospheric pressure.

Can you speak to V. HUck about that for clarification?

Hi Jeff,
there are 3 different types of 'Saugrohrdruckfühler', maybe called MPS or MAP sensor (didn't realize a difference before, I'm no native speaker...)

The first type, installed in very early Volkswagen and later only Citroën, is combined with an absolute pressure sensor in any setup.
It has aneroid cells installed that don't correspond with the air pressure outside because the housing is fully sealed.
This hence can not take the atmospheric pressure into consideration at all.

The second type, installed in most 914 (model without the black cap) has aneroid cells installed that don't correspond with the air-pressure outside. But the full-load-diaphragm installed in this type can correct the full-load-curve depending on the outside air pressure a little bit.
Unfortunately, this diaphragm gets leaky after some wear, 'type II'-sensors tend to go defective much more often than the other types.

The third type (installed in late cars, model with the black cap) has one vented and a second non-vented aneroid cell installed, hence can correct the curve depending on outside air-pressure, does altitude compensation.

Unfortunately, you can't install a 'type III' instead of a 'type II' - sensor because then the full-load-enrichment-function is missing that is done inside the sensor at 'type II', but done by the TPS at 'type III'

----

But - maybe I didn't understand your annotation in full. Contact Volker directly- he is always interested in eliminating errors or misunderstandable statements.
And - he speaks much better English than me.

Regards
Norbert

--- Following the link https://oldtimer.tips/en/d-jetronic/55-mapsensor, you will find a list of all D-Jetronic map-sensors and their features, page down, section 4.5ff

Thank you Norbert, I will contact Volker that when I get a chance,, he seems very knowledgeable. I was aware of the other pressure sensor types, but being a 914 guy, the only one I had the most exposure to is what you refer to as the type II MPS.

Yes, Jeff - you are absolutely right.
I checked this in the meantime- only 'Type II'-sensors in various versions have been used originally in the 914.

Maybe some 914 have installed the TPS with the full-load-switch, but this is not connected then. Only four wires towards TPS in a five-poled housing perhaps.

Regards
Norbert

Hi Jeff,

that is an interesting question and I only see it now when I surf through links to my website. Let me introduce myself: I am an D-Jetronic enthusiast naming myself Dr-DJet and I run the forementioned webstite oldtimer.tips with the D-Jetronic compendium and a forum dedicated to D-Jetronic of all manufacturers.

It is a pity that this question never made it to me. I admit that I was not aware of the English acronym differences MAP and MPS. But you will see that I am not so wrong either and not 100% correct too.

As you already noticed there were three types of vacuum pressure sensors. Type 1 (as seen in early VW type 3 and Citroen) has 2 evacuated aneroid cells and it measures absolute pressure, nothing else. So it is a MAP sensor.

Type 2 also has 2 absolute pressure aneroid cells and like type 1 it measures absolute manifold pressure. But then we have the full-load diaphragm which opposes some environmental pressure on the armature shaft. It is only a smaller side effect. Type 2 is not meant to measure differential vacuum to environmental pressure, but it still has a slight influence. For that reason I have to adjust environmental pressure and absolute vacuum when I adjust one of them. I would still call type 2 a MAP sensor. This is the type you all ride in 914s. After 40 years diaphragms tear in this type and I just made a nice video how you check that.

Type 3 (latest version in many cars like my MB 450 SL) has a differential pressure cell AND an absolute pressure cell. So it is a MAP sensor and a differential vacuum pressure sensor (MDPS if you like) at the same time. Here I have to measure absolute vacuum and 2 environmental pressures to verify/adjust a type 3 pressure sensor.

So the question is whether you want to nag about me calling type 3 sensors a MAP sensor. There I am only correct for one of the 2 cells. In type 1 and type 2 I am correct. If there is no further errors, I can live without it.

In total I prefer to call all 3 D-Jetronic vacuum pressure sensors MAP sensors. I hope you do not mind. I would also welcome you to my forum to discuss such interesting questions in more detail if you like.

Best regards,
Dr- DJet (Volker)

Still looking for the instruction...

Regards
Norbert

Hi, yes, I have that very same tester, and probably have some instructions. It's not too complicated. Let me see what I've got and I'll post another response.

OK, I just went and looked, and like you, I don't have any instruction manual for it. However, it shouldn't be too hard to figure out how it all works. Mind you, what follows below is from my experience with such testers, I have not used it on my car personally. I have a somewhat similar tester from Kent-Moore that has similar features, but it has a guide in the lid (will post pic below), some of my interpretations come from that guide.

Note that the car is assumed to have been run prior to the test and is at operating temperature. This is important for a number of the tests that follow.

My unit is serial number 128.

The first thing to notice is that this tester plugs into the wiring harness, but NOT into the ECU. Many D-Jet testers connect to the system with an interposer, so that they can test both the ECU and the other D-Jetronic components (e.g. VW1218). The Ditron 812D does no ECU testing, and in fact, substitutes for the ECU in some functions.

The unit has a switch on the RH side for 4,6 and 8 cyl operation. This switch determines the injector groups used. The ECU fuel pump control, which is normally 1.5 sec when switched on, then constantly on when the car is running, is replaced by a simple fuel pump switch which toggles the pump on or off.

There are various indicator lights. The early throttle switches (1968-1969) had an idle switch, and there was an additional vacuum-controlled pressure switch. When the throttle is closed, the "THTLE. SW." light should be on, and should go off when the throttle is opened by more than 4 degrees. When more than 1 or 2 inHg of vacuum is present at the pressure switch, the "PRES. SW." indicator should turn off.

The later throttle switches (1970) have an idle switch (THTLE. SW.), and two inter-digitated switches for fuel enrichment (F/E) injection pulses (F/E 1, F/E 2). The throttle is taken from closed to fully open to show the operation of the idle switch, and 10 flashes on each of the F/E lights.

There are also lights that show the starter signal (when the key is turned to the start position), and battery voltage.

There are four knobs on the tester and an analog gauge, as well as a push button. The central knob on the top of the unit has settings for "AIR TEMP. SENSOR", "ENG. TEMP. SENSOR", "TRIGGER POINTS", "FUEL INJECTORS", "PRESS. SENSOR", and "RUN/DWELL". Each of these settings are described as follows.

"AIR TEMP. SENSOR": The air temp sensor is switched in to the meter to indicate its resistance as a function of air temperature. The meter range is marked, and it covers the operating range of air temperatures expected. Readings outside of this range indicate a problem with the sensor.

"ENG. TEMP. SENSOR": The engine temp sensor is switched in to the meter to indicate its resistance as a function of engine temperature. The meter range is marked, and shows ranges for water-cooled engines and air-cooled engines at operating temperature. Readings outside of the associated ranges indicate a problem with the sensor.

"TRIGGER POINTS": The Ditron 812D and the Kent-Moore tester differ in operation with this test. The Kent-Moore tester has a "START" push button that substitutes for the start signal from turning the key to the start position. On the Ditron 812D it is necessary for an assistant to turn the key to start during this test. Depending on the D-Jetronic application (4, 6, or 8 cyl), either 2 or 4 injector groups are used. These injector groups are selected using the top left knob, and turning it to positions I, II, III, or IV. At each of these positions an assistant turns the key while the meter is observed. The reading should switch between "OPEN" and "CLOSED". The dwell is tested later. Note there is also a knob setting for "INJ. FLOW". In this setting, when the "ACT. INJ." push button is pressed, all injectors will be opened and fuel will flow. This setting can be used to verify injector fuel flow and spray pattern.

"FUEL INJECTORS": Operation of this function is unclear to me and will require testing on a car to verify. If this setting is similar to the Kent-Moore tester, it may be a way to determine if each of the injectors flow the same amount of fuel. I cannot comment further until some testing is done.

"PRES. SENSOR": If this function operates as it does with the Kent-Moore tester, then it indicates the response of the manifold pressure sensor over a range of vacuum from 0 inHg to 15 inHg. Disconnect the hose to the manifold pressure sensor and connect the sensor vacuum port to a hand vacuum pump with a gauge calibrated to inHg. At 0 inHg, the meter should be at the far right of the range labeled "PRESSURE SENSOR". Pump the sensor down to 15 inHg, the gauge should move to the far left of the range.

"RUN/DWELL": In this setting the 812D substitutes for both the ECU and the MPS in the operation of the engine. Set the upper right knob to "RUN DWELL", set the "TRIGGER POINTS" knob to I, and detach the hose from the manifold pressure sensor and plug the hose. Set the "MIXTURE CONTROL" knob to mid-range if the engine is still warm, and further to the right (rich) if the engine has cooled off significantly. Turn the "FUEL PUMP" switch to on, and have an assistant turn the key and start the engine, some throttle opening and adjustment to the "MIXTURE CONTROL" knob may be required for best results. In this mode, the dwell of the trigger control points can be measured and compared for each injector group. Turn the "TRIGGER POINTS" knob to each injector group and compare the reading in the "DWELL" zone of the meter, all of the groups should be the same.

That's my best take on how this tester works, it should be easy enough to connect it to a car equipped with D-Jetronic and verify these tests, or figure out what they really do. Experiment always trumps theory, as they say. Let me know what you find out.

My Ditron 812D Tester

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My Kent-Moore 112D Tester

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Kent-Moore 112D Test Checklist (inside lid of tester)

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Only the MPS used for the Mercedes-Benz applications is able to compensate for atmospheric pressure differences (i.e altitude and weather). Your interpretation is correct, and I believe Volker explains it well in his response to your question.

Actually, as Jeff and many of us know, the MPS can be "tuned", meaning that it can be adjusted to factory specifications, or the specifications can be precisely set for specific running conditions. Details of the process are on my site, and Jeff and others have used these procedures for years as part of rebuilding MPS's and adjusting MPS's that have been "fiddled with" by others. There are a number of rebuilders who have been doing this for years, such as the old Bret Instruments outfit (since bought). The guy who ran it had a long phone conversation with me some years ago where he described the bench setup that he used to take "golden units", aka NOS MPS's, and come up with parameter sets that could be used to calibrate rebuilt units to the same characteristics.

Note that while there are many MPS's, with a number of feature design differences, such as varying types of damping devices, presence or non-presence of full-load diaphragms, etc., our experimentation here in the 914 world has been restricted to the MPS design used for our application: the dual-aneroid cell, full-load diaphragm model. For this model, there are three adjustments that can be made: part-load mixture (central adjusting screw), full-load mixture (full load stop), and part-to-full load transition range (outer adjusting screw). Procedures are given on my page on how to make adjustments and what the expected effect on mixture will be.

For "tuning" applications, the MPS can be adjusted while the car is on a chassis dynomometer and connected to an AFM meter. This can assure ideal operation of the system across all running ranges.

In cases where the volumetric efficiency (VE) of the engine has been significantly altered (e.g. different camshaft, valve sizes, displacement, boring of the throttle body, etc.), adjustments to the MPS will not be sufficient to compensate for the changes in the VE curve, as the MPS is blind to the VE curve effects on mixture. In these cases, the most practical solution is to fit a modern speed-pressure EFI system to the car and remove the D-Jetronic system, as modern systems incorporate VE mapping (e.g. Megasquirt and others). If you really, really, want to retain the D-Jetronic system, and the changes to the VE curve are not too radical, then it is possible to modify the waveform generator circuits on the daughter card in the ECU to accommodate the altered VE curve. I believe this was the initial motivation of Frank Kerfoot, who developed the ECU circuit diagrams we used to reverse engineer the ECU. He was doing SCCA racing and wanted to get an advantage over his competitors, yet stay legal in his classification. Not sure it it worked or if he ever actually did it!

Hey! I just went and looked at my own page on the Ditron 812D, and you know what I saw in the picture of the tester? A manual! So, maybe I didn't find it when I just went and looked, but I'll go look again and I'm sure it's there. I'll fill in the gaps in my explanation of how it worked once I see it, and if it's not too much trouble, I'll figure out a way to scan it and get it to Norbert. EDIT: yeah, I've got it, and most of what I described earlier is accurate. It's not too many pages, I'll scan it and make it available. May take a bit to get it done, will update when it's ready.

Here you go. I scanned it with the document reader, so there are some blank pages that you can ignore, but everything is there including the test setup and test procedure.

http://members.rennlist.org/pbanders/Ditro...on%20Manual.pdf

Thank you so much for all your work and explanations, Brad.
There are some other cars / manufacturers equipped with sensor 'type III' with compensation - late Volkswagen type III, Opel (GM), Citroen, Jaguar.

Sorry, I have no time left at this time, will add explanations etc. later.

Regards
Norbert

Hi Brad,

good to see you here. I am still hunting for the EFI 9100 you mention in your website. However I believe that I also have some nice even Bosch internal testers that are even superior to that one. If you want, have a look at Bosch KD-JE 7400, 7401 and 7402 or the later MB version KD-JED 7500.

Best regards from Germany,
Dr-DJet

Hi,

when I just see the comment on pressure sensor altitude compensation. I call it the type 3 MPS. It is available for Volkswagen Type 3 and many other cars. MB used it on their 280 and 450 engine, but not on 250 or 350 engine. Many OEMs like Opel switched at one point of time from type 2 with diaphragm to type 3 with altitude compensation.

I even made a list with all available MAP sensors at list of all pressure sensors on oldtimer.tips. I also built up references for tuning them to original. Same for ECUs.

Your comments are welcome.

I own an EFI Assoc 9100 for D-Jet and 8100 for L-Jet, with operating manuals. Formerly owned by the late John Larson. They are very capable testers as you know and do include a vacuum pump on the stand, separate from the tester unit.

Hi Jeff,

I glanced through the EFI manual and therefore know its capabilities. But the Bosch internal KD-JE 7400 is superior to it. It tests ECUs very deeply. Bosch first produced them for intenal usage only. I even believe that they were used in manufacturing ECUs for tuning them. Around 20 of them were finally installed in premium Bosch workshops throughout Europe at that time. They are extremely hard to find. I think there was none in the US.

The EFI 9100 has similiar features to the one that Bosch made for Daimler. That one was called KD-JED 7500. It does not test as deeply as the 7400.

Anyhow: If you or someone else would like to hand over his tester to a collector, please let me know

Hi Brad,
thank you so much for doing the scan-job...
I did a clean-up at the document and deleted the empty pages. I then realized the last page doesn't belong to this manual - maybe it belongs to the Ditron 811L (L-Jetronic-tester).

I already had most of the information before - from your page and the informations I got about the Kent-Moore-Tester.

But the 'paper' I now got from you gives me much more information about the tester - regarding the intention of 'Ditron' to tune and repair the MPS using this unit.

I knew before the Ditron isn't able to diagnose my car in full - because my car has the full-load-switch integrated in the TPS. The Ditron doesn't support testing this.

But the VW 1218 can do this - because the late VW Type III has such a switch, too.
But this Tester isn't able to test the injectors for continuity - i.e. not that ones that are paired in 6-cyl. applications.
Nor can it test my ECU - my car doesn't have an over-run-shutoff function.

(I don't really need this testers, but it is my interest to find out the specific differences between the differen D-Jet-applications...)

Nor do I want to 'tune' the components of my car. I own some ECUs and MPS with the same Bosch-part-# - but my car runs best with the 'original' components.

We found out Bosch didn't report 'mininimal changes' done to the parts to all of the car manufacturers and/or these didn't inform the workshops.
Nor are these changes to be found in any document...
At BMW, for example, parts are marked with red / blue points, Opel parts aren't marked.
Installing a fully operating and fully-tested MPS with the same Bosch# can result in an engine with highly reduced performance.
Therefor the encoded production date on the units is quite important for us Opel-guys <most of them don't know...>.

--------

Volker Huck does the MPS-repair the same way you reported, using the values taken from 'golden units' - as many of them as he can get.

--------

Concerning the tuning the D-Jet-Equipment of modified engines we have an additional idea, too.
Three decades or so ago a company in Germany developed an additional box, meant for adding an catalytic converter to the D-Jet-system, using an O2-sensor.
This high-priced unit 'ST28' produced by G+M, Gladbeck is available up to this time and could solve all the problems.
You can see a figure here (identically suitable to other D-Jet-cars): https://oldtimer.tips/en/forum2/jetronic/15...g?start=20#1359

Best regards and again

Norbert

FWIW, if anyone is interested, I just put up four testers for sale in the classified forums: a Ditron 812D D-Jetronic Tester, a Janbo 112 D-Jetronic tester, a Kent-Moore 112D D-Jetronic tester, and a real rarity, a Ditron 811L L-Jetronic Tester, for you 1.8L 914 guys who need to check your cars out. Take a look if you're interested. I don't use these testers and I'd like to see them go to someone who can put them to good use.