Amen. You'll need a special pressure gauge set to diagnose, too-- with banjo bolt fittings and a valve to compare line pressure and control pressure. I'll bet you did! That is the single most over-priced German work of art I have ever seen in my life. There's only one moving piece inside: a metal diaphram. After millions (?) of warm up cycles, it ruptures. In the turbocharged version, the failure is even more exciting due to an extra sensor port open to ambient air-- fuel pours out literally as fast as the pump can deliver it. (If you ever needed to know, that's about half a tank, during the 20-mile drive it took the owner to bring it to me...)

My parts guy quoted me $278 for the regulator. (2 decades later, I still remember it.) You're kidding, I said..... I found a piece of spring steel, 1" square, approx 0.002" thick, and it worked great... for about a month. Then it ruptured again. I asked the parts guy if I could purchase just the diaphram, he said he knew exactly what I was talking about, he had already had this conversation with a buddy who worked at the Bosch repair dept... that guy told him, "I have a whole bin full of those things right in front of me, but if I let one out of the factory, I'll lose my job." So, no choice but to purchase the entire work of art.

If your pockets are deep enough to buy a bunch of brand new parts so that you're not driving a reliability question mark, you could be happy with the system for quite awhile. Find the K-Jet with lambda if you want to be able to adjust it to fit a different engine-- without the feedback of the O2 sensor, you don't have much hope. And that's just for closed-loop cruising-- I honestly don't know how adjustable is the warm up curve, the idle air valve (yes, it's thermo-mechanical too), or the WOT condition. I suppose anything can be tweaked, but I'd sure want it to be pretty darn close, before trying. Otherwise, you won't have a car, you'll have a hobby.

Ever try to tune a piano, get the equal temperament almost right, realize you could sweeten up one chord with a tiny tweak to one note... and immediately discover that 4 other chords suddenly sound sour? Uh-huh. Everything is connected to everything. Same with this.

Overall, CIS in good shape can run pretty well, but compared to EFI, the idle is a little more finicky (the speed vs. temperature isn't quite as repeatable, especially if you start it when the engine block is warm and the air passages are cold, like if it's been sitting for an hour or so-- fuel control pressure and IAC aren't in sync for a couple of minutes.) And the emissions aren't quite as clean. But here's the biggest deal-breaker for efficiency: you won't have Fuel Cutoff during coast. I've found that Cutoff can add at least 1 and sometimes 2 mpg per tank average, IF you take advantage of it in your driving habits (double clutch on the approach to every stop sign to keep the RPMs up, etc.)

Gosh, I hadn't thought about the CIS system in years. If you go for it, good luck! The Bosch engine management book, as with everything I've read by the late Charles Probst, is extremely useful.

- Erik

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Lots of early Valiants and Barracudas have crossed my path.
Also a handful of other toys for variety now and then.

You make it sound like the problems were common, but that was maybe because your work was to deal with them! The fact is that most of the MB cars went 2-300,000 kilometers or more without any issues, but when the problems came, they could be massive. I agree to the cost issues, but I think it is partly because most owners needed a trained mechanic to get the car in order again, it wasn't like a carb that could be cleaned and made to work again with little effort. I think that a K-jetronic is not something everyone should try to adapt, it demands detailed knowledge beforehand.
I totally agree, the emission issues were probably why the manufacturers went for injection systems in the firstplace, and the progressively tougher regulations led to the 2nd generation of K-jetronic and KE-jetronic, which were lambda-sensor controlled. The mechanical simplicity of the first K-jet is facinating, but the workmanship and precision in details are impressive, and must be dealt with the right way. There were also differences between setups for different makes. Volvo, for axample, have CIS (not Continuous Injection System, which is an american abbreviation, but Constant Idle Speed) add-on:
Not correct, at least for later Mercedes (230 and 280 123-series after '81) versions of the mechanical K-jet. My engine has fuel cutoff at speeds above app. 30 km/h (~19mph), if I let off the gas pedal at say 50 km/h and just roll, I can faintly feel when I come down to the re-actuation point.

Olaf

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Aspenized

That must be the later KE-Jet, then? Ah yes, I see as per Probst, the additional electronics offer that feature.

In looking at diagrams, I can't think of a way that the original K-Jet (mid-70s) would have had enough inputs to know how to cut off fuel entirely, with no RPM sensor and no control module. In that case, it seems like the KE-Jet might be a more promising starting point, for those bent on rolling their own.

- Erik

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Lots of early Valiants and Barracudas have crossed my path.
Also a handful of other toys for variety now and then.

Imagine the cost reduction that going to EFI was on these cars. 6 mass produced 1 moving part injectors, same fuel pump, regulator, a few sensors and a mass produced circuit board that was probably 30 bucks/pc by the 10000. Forget all that precision machining and assembly. Progress.......but I bet this still wil work after a nuclear EMP hits it. Zombie apocalypse vehicle!

Nope, it is a 1985 (built 1984) S123 230TE Wagon, 2.3 ltr. M102.980 engine with pure mechanical K-jetronic, including the fuel cut-off which was introduced in '81. The cut off consist of a relay activated by high vacuum and a switch on the throttle shaft mechanism, when the throttle is closed. The relay opens a vacuum actuated valve, which lead air in a hose directly from the air cleaner to the intake runners, bypassing the air measuring plate, thus 'fooling' the regulator to cut most of the fuel supply, until vacuum fall below a certain level. Very simple, very ingenious, and it works!

Mercedes actually used a similar system to save fuel on the carburetted versions as well, it simply turned off the el. fuel pump!

The KE-jetronic came on the 1985 'E' 124-series, the 123 and 124 series actually ran parallel for one year.

If I can get hold of a complete setup from a six-cyl. 280, I will try to bolt it onto a SL6. The 2.8 ltr. MB engine has 185hp, and if necessary, the K-jetronics can be adjusted to deliver enough fuel to support a 30% increase in output, in stock form. The 4-cyl version, shown below, supply a 136hp engine, so it should in theory be more than enough for a stock SL6.
For testing, a complete system, with throttle valve, could be mounted on a super six manifold, with the 4 injectors installed in an adapter plate so they just spray into the plenum, or onto the hot manifold floor for max evaporation. Mechanical TBI!



Zombie apocalypse vehicle!

Olaf

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Aspenized

Olaf, you pull this off and itll be a new dawn for FI slant options. This looks like almost a bolt on! I never drove a big Benz, just my roommates '70 280S on a beer run, but it had smooth power from off idle on up. I never could get over the huge rear end drop when you put it in drive. I thought I broke something. THese were never dirt cheap in America so we didnt grow up wrenching on them, you could buy a 70's Valiant for $500 bucks and it would run forever.

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I didn' t buy it, I built it.....

These were never dirt cheap anywhere, especially here in Norway where the import taxes are sky high! All the wagons have automatic leveling rear suspension, a dipping rear end on those, is a clear sign of major expences coming up!
I agree, the more I have thought about it, the 4-cyl version set up with injectors to the plenum seem as close to a bolt-on as you can get, except I need a bulge in the hood to make it fit, and a setup with original fuel pump, filter and accumulator. The best would of course be a 6-cyl K-jet version with injectors in each runner, so I think a test would be just to see if the air measuring system itself works OK over the entire rpm range on a slantsix. BUT, unless it is an improvement on a good carb, it will be more of a hobby project done because it is possible to make it work! (and that is usually good enough for me! )

Bad news is, that the were no offical US-versions of the 4-cyl engines, so the 230s avaliable in USA are private imports, you have to look for 280E/280SE/280TE 6-cyl models, prior to '85. (or 500SE/560SE for V8s) The Volvo K-jetronic for the 2.1 and 2.3 ltr engines also supply fuel for ~140 hp in stock form, but they use the lambda-sensor versions, and since the main point is a mechanical setup with injectors in each runner, the 4-cyl models are worthless. And as Joshua Skinner said, the 6-cyl version is a no-no! I am not familiar with the versions used by VW, Audi and others.

Olaf

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Aspenized

Yep! Kinda like how a doctor sees lots of sick people! Almost everything European had CIS/K jetronic injection. VW, Audi, MB, Volvo, etc. Funny thing is, once Bosch went to later electronic versions (CIS Lambda & CIS-E here in US) I generally saw fewer problems overall. The most failure-prone mechanical parts were replaced by sensors & the ecu.

If the OP has enough time, parts, & determination, then by all means proceed with your venture! (I'll stick to what I know- EFI)

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63 Valiant Wagon
225 - 4 bbl

First and foremost, I am a carb man! But I love to play with tech solutions, especially if the are pure mechanical, and the mechanical K-jet is something I know a little about, but I am far from an expert. As I wrote, it will be interesting to see if the air valve system can produce an even fuel/air mix over the entire rpm scale for the SL6, with the injectors and an air inlet for the fuel cutoff, placed in an adapter plate. I also think that a simpler solution for fuel distribution could be designed or adapted, the precision in the Bosch unit make it difficult to work with, as I am sure you know very well!
But, members of the slantsix community are not known to be afraid to play with odd solutions, and play is the leading word here!

Olaf

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Aspenized

I was speaking specifically of the analog electronic D-Jetronic system which preceded the K-Jetronic. The 6-cylinder K-Jet/CIS I feel would be fine.

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Joshua

I am sorry for not being more spesific in words, Joshua, D-jet is what I meant to refer to. I don't know if 6-cyl Volvos ever used the pure mech. K-jet, I think they all used a K-jet with a lambda sensor, the predecessor to the KE-jetronic, but I haven't looked it up.

Olaf

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Aspenized

The injected Volvo 164s were all D-Jet if I remember correctly. The V6 equipped 264 would have needed to be lambda equipped just like anything else in the US with a catalyst. The V6 cars didn't last long though as Volvo seemed to prefer turbocharging their 4 cylinder. A Mercedes 280 is probably the most likely donor, but at this stage in the fuel injection game I would go electronic so that you aren't dependent upon expensive and increasingly difficult to find parts.

Reed may have won me over to mass-air-flow metered EFI, but if the 6 cylinder Ford ECU is a one-year-only deal I question whether or not Megasquirt might not be a better ECU choice.

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Joshua

Yes, the 164s were D-jet, I meant that those with a K-jet never used the mech only version.
For me, the price of the toys is my main concern when I'm playing, and I can get the Mercedes pieces for free, or very cheap. Cannot beat that!

Olaf.

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Aspenized

found a cool Bosch MFI schematic. Chime in on what the numbers are.

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I didn' t buy it, I built it.....

Looks like the L-Jetronic system BMW used on their 4-cylinder cars in the 80s.

1 - Fuel tank
2 - Fuel pump (some models have 2 pumps)
3 - ?
4 - Fuel filter
5 - Fuel pressure regulator
6 - Fuel injector
7 - Throttle body
8 - Injector for cold start enrichment (later models don't have this)
9 - Air filter housing
10 - Air flow sensor
11 - Air temp sensor
12 - Oxygen sensor
13 - Intake manifold?
14 - Water temp sensor
15 - Distributor
16 - Idle air valve
17 - Throttle position sensor (only registers closed, WOT or "somewhere in between")
18 - Main ECU
19 - Might be the idle ECU. Later models do this in the main ECU
20 - Battery
The box to the left of #18 is probably the main relay.

The Motronic system in my 6-cylinder '88 seems to be pretty reliable. It's set up pretty much the same way.

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'64 Dodge 440
'65 Dart wagon
'14 Chrysler Town and Country