Fuel injection part? Help ID ing 311906019

[Ceckert64]

So I have this part that I found at the junkyard, it looks new and I feel like I found in lying around. It’s part 311906019 in the VW system. I believe it has something to do with adjusting the idle or mixture on fuel injection computers/ cars. It has three wires coming from it, a brown a white and a green. I know some late T4 d-jet computers have this piece built in but I’m guessing this is an accessory part that could be installed on earlier cars that didn’t have it. How would it be installed or tied in to the system? Any info on it?

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1964 sunroof Beetle Restoration "Herbie"
“Joann” 1970 Elm Green Squareback
1972 Sierra Yellow Tin Top Westfalia Camper
“Fitz” 1971 Westfalia Poptop

[KTPhil]

Kinda looks like the E-generation ECU idle CO adjustment, but the form factor isn't quite right for that installation.

[raygreenwood]

Interesting!

In the type 4 cars (411 and 412)......our "E" series ECU's came with a knob identical to that built into the ECU. It typically has a range of 24 clicks....12 on each side of the center detent and is for adjusting idle mixture only. Once the throttle valve switch clicks open.....its out of the loop.

I have never seen one seperate from an ECU. A type 3 only thing obviously!

Where does it wire into the system?

Ray

[KTPhil]

[Bobnotch]

You might try sending Jim an e-mail, and see if he could help you. Maybe Dave Hall might know more about that too. It's worth asking about.
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Bob 65 Notch S with Sunroof
71 Notch ...aka Krunchy; build pics here;
http://www.thesamba.com/vw/forum/viewtopic.php?t=249390 -been busy working
64 T-34 Ghia...aka Wolfie, under construction... http://www.thesamba.com/vw/forum/viewtopic.php?t=412120

[Tram]

This is an interesting find for sure!

I've never seen it or heard of it, but there are several clues here that may point us in the right direction.
1. Parts group 906 indeed puts us in d-jet fuel injection.
2. There's a hole in the bracket for remote with a sheet metal screw mounting somewhere in the engine compartment. The rubber cover tells us it goes in an exposed area as well.
3. The green wire means switched power, brown is earth or ground, the white seems to match the FI harness.
4. If I am seeing it right, the white stamp is "69", indicating a date stamp.
5. The lack of a part number suffix indicates first- or ONLY- generation of the part in question.

Assuming all of the above is true... WTF is it? It definitely seems to be a potentiometer of the later 914 or Type 4 kind. It's not Volvo or MB, it's definitely VW, and Type 3 at that.

If the date stamp is indeed 69, it predates any known D-Jet ECU potentiometers by a few years. What was different about 69 that might require this part?

I think the most likely answer is the optional cold start enrichment system offered on the 1969 B cars for cold market buyers. The enrichment system didn't come about because the FI system as it was designed couldn't handle brutally cold temps. It came about because of battery and oil technologies of the time. Batteries then could lose as much as 50% of their cold cranking capacity at below zero temps, and oil could turn pretty much to treacle.

Since the FI system needs a minimum voltage to operate, owners found themselves with no- starts in arctic climates because there wasn't enough juice to run the molasses in the crankcase AND fire the FI system. So- the idea was to shoot some raw fuel in the intake, get it to fire and get the generator spinning- and away we go.

I think that maybe this piece could be used to vary the duration/ amount of cold start injection slightly for colder climates like Sweden or northern Canada, or Alaska.

I could also be completely full of crap.
Where's Adney? Wonder if he's ever seen this.

Incidentally- Harold Glenn's FI guide- a fine publication- indicates that ALL D-Jet cars got the idle CO control in 1972. Yet, I have NEVER seen this on a Type 3. Anybody else?
See PP 28-29 here:
https://www.vwtypethree.com/downloads/pdf/Glenn-FI-Type3.pdf
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Немає виправдання для війни! Я з Україною.

[KTPhil]

Here is his photo, which sure looks like it, except for the mounting tab with a hole.

Until I saw this, I was thinking maybe that tab was for internal mounting in the ECU. However, it would not fit in the box mounted as shown. So I agree, it's for external use.

Any chance this was part of test equipment, not a field install on a car? It might get a Type 3 number in that case, though usually tools were not in that parts group number series.

If I knew what circuit this modified maybe it might be a clue to how it got used. If it was simply a graft to modify a fixed resistor, maybe it could have been a field retrofit. No schematic for those late units I can find, though.

I've never had that "E"-generation ECU in my hands to know when they were fitted from the factory. I heard '72 but can't verify. Maybe a California thing? Those models, automatics in particular, had some weird stuff not seen elsewhere (EGR, spark limiting, dashpots, etc.).

The ECU listings only show one version ("E") for the '72-up model years. However, unrelated to this change, there were variations with a black sticker that modified the resistance from one of the temp sensors, starting in '70, well before there was the "E" ECU with the dial.

This is high up on the "what's this part" contest...

[KTPhil]

Ok, this photo shows the factory dial installed at the upper left corner, clearly not mounted as the subject part at the top of the thread would be. It does have the same three wires, though. Unfortunately, I cannot figure out the correlation between the leads/thru-holes in this board photo and the schematics. The site notes this is from an 8-cylinder Benz engine.

The source site for this photo makes for fascinating reading!
https://jetronic.org/index.php/en/d-jetronic/53-ecu

One quote explains the extraordinary reliability we see in our ECUs (note: the short history of this system is that Bendix tried to make it work in the mid-'50s, gave up on the components of the day, and sold the basic design/patent to Bosch, who had the stubbornness to see it through to production):

"After Bendix's experience with drifting and unreliable components, Bosch even used MIL-spec components. And that has paid off, as this electronics is, despite its age of 40 (now 60) years, very reliable."

[KTPhil]

From Brad Anders site (geared mainly towards the 914 D-jet system, but most of it applies to us):

Idle mixture can be adjusted by using the idle mixture adjustment knob on the ECU. Note that some early 1.7L ECU's did not have an adjustment knob. Clockwise clicks richen the mixture, counter-clockwise clicks lean the mixture. The factory made a mark on the plastic surround of the knob to indicate the "factory" setting, the correct mixture for proper operation is usually within +/- 3 clicks of this position.
It has no effect unless the throttle is closed and the idle switch in the TPS is on, indicating the idle condition.

It is discussed here:
https://members.rennlist.com/pbanders/ecu.htm#IM

He identifies IA (Idle Adjustment, the part we are discussing) as a "5KΩ adjustment potentiometer."


The two scope photos below (sorry for the poor quality) show the effect of the IA potentiometer position (measured at point 15 on sheet 3 of the schematic) on the combined IM+SC output for a 0 280 000 037 ECU under test at idle conditions.

Total voltage shift range is about -0.6 V going from fully counter-clockwise to fully clockwise.

On most ECU's with an IM knob, there is a small mark in the plastic surround of the knob that was put there at the factory. This mark identifies the balance point where the IM adjustment has no effect on the level of the output of the SC circuit.

Here is the "sheet 3" he is talking about (location W-28):

So it appears it is associated with the MPS terminal 10 signal.

See location H-25 here:

[raygreenwood]

Yep...got back to this too late

The red arrow shows teh "wall mount" tab and the yellow arrow shows the stop block on the knob (this one is turned all the way lean) and the green arrow shows teh neutral detent in the middle.

The actual detent ratchet is on the left end of the ring surrounding the knob.

Yes they usually had a "dent" in the ring around the scale to mark center neutral position.

Ray