Make LH Jetronic motor run K-jet. Possible?
 

I’m just curious if I could take simpler k-jet setup and put it on a 1993 m104 from a 300se w140 (3.2) to possibly put it into a more vintage car. I’ve got a manual trans that I’ll bolt up, but doesn’t have crank position sensor stuff. Maybe I could get magnets welded to the flywheel and take the whole electronic ignition from the w140, but I want to look at all my options.

I’ve got several k-jet m103 cars that run, some better than others. I’ve got a bunch of m110 too, but the problem with basing my setup on m110 is the lack of an old-school ignition distributor.

The first problem I envision with m103 k-jet stuff on an m104 is the injector hole sizes. Is that an issue?

Any other issues or solutions you guys see other than a megasquirt or something tat costs more?

(I’ve got full access to a MB shop-junkyard with ~40 cars.)


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* Since M104s were supplied with Kjet, the manifold is available.

* Irrespective of the source of the Kjet metering components, you will be looking for an ignition system.

The M104 with CIS / K / KE Jet ( 89 - 90 ish 300SL / 300CE ) uses a different cylinder head than the LH / ME 2.0- 2.1 FI system. The intake manifolds are not " officially " interchangeable without mods / spacer plate due to the port shape being different. There is a chance they might " work " but flow will be reduced. Have a look at intake manifold gaskets.

Also be aware, that on CIS / K / KE Jet air flow meters, the shape of the funnel dictates shape of fuel curve. You will not be able to tune a straight mechanical K jet without making a new funnel.

Early 80's SAAB and others used a " buzz valve " to alter control pressure per the O2 sensor, however, this is now old $$ stuff.

Rather than going to a " works when new but not so well when worn out " system with $$$$ parts, move to a late 80's GM multi port system. With a bit of digging you will find the PROM has been cracked long ago making it easyish to tune.

Sure, is isn't like a modern aftermarket EFI where you tune from a lap top but, it is low $$.

Come to think of it, look at newer OE multi port systems, surely someone has cracked one making it tunable with a lap top.

Edit, The V8 stuff won't work on a 6 .

Another thought, Caddy Northstar. This is V8 multi port and DIS.

Thanks guys! I hadn’t thought much of the flow rates and curves being all wrong.

Thanks for the GM concepts. I don’t know automobile stuff other than 1985 and earlier MB cars, really only about 1972-1985 really, d-jet and I-jet. I realize that GM stuff probably isn’t hard to learn, but like to keep my addiction fairly focused. I don’t want my Mercedes to become a gateway addiction. It’s already bad enough. I’ve all heard of 80’s corvettes being swapped to carbs bc either the FI sucked or whatever.

How about taking the whole w140 wiring nonsense?


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To edit my post 4, I was thinking V8 when recommending the Caddy stuff.

For a 6, a GM 3800 Buick FI system with coil packs would be better. These could also come with a supercharger making a boosted M104 easier. Using a 2000 era 3.1 L front drive would be possible.

There are probably newer systems that have been cracked so going new as possible would be better. I'm a bit out of the loop on the latest and greatest so do some searching if you want to know more.

No matter what system you move towards, there will be some learning because every system will need tuning. A carb sort of self compensates due to air flow ( analog ) , electronic FI needs to be told what to do.

D and L jet is long obsolete and parts are $$$.

The point of using GM is ease of purchase and low cost at the salvage yard or auto parts store. This is an advantage over an aftermarket system that you would have to learn anyway.

The 80's Corvette / Camaro could have been gotten with " Crossfire Injection ". This was pretty much 2 single barrel throttle bodies on a short cross ram intake. The system was MAP ( manifold pressure ) based so changing a cam / exhaust changed intake manifold vacuum causing the fuel curve to be all wrong.

Also, some tend to remove systems that they don't understand. I've seen plain old distributor type electronic ignition removed and replaced with points.

What are you wanting to do with the W140 wiring?

The w140 seems to have good wiring. I have no damn clue about w140, and have shied away from any 90’s MB after realizing after the sale that my 1992 500sl had bad wiring inside the cabin. Apparently the biodegradable wiring is everywhere in 90’s benz, not just the engine bay stuff tat everyone talks about. So no W124, r129, w140 or any of that stuff for me anymore.

The car was dirt cheap. I thought I was going to buy a car with a reconstructed title, but the guy pulled out a salvage title. There’s a big difference of proving that the car is good enough for the road. I’m not interested in doing that for a w140 with no reverse and a massive power steering leak. The handling of the car and the power really impressed me though. The 3.69 rear end (and OD trans) definitely helps with the power feel. But it is supervising to feel a 6 cylinder motor get such a big car moving so well.

Anyway, I only moved forward with the purchase because it seemed the m104 was in pretty good shape, and I didn’t understand how complicated a transplant might be. I got a 5 speed 4-cyl w201 delivered in exchange for a few catalytic converters. I know a guy tat put the same trans on the same motor and put it in a 6-cyl w201. I’d be more interested in putting it into something more vintage, like:
- w108 (but m119 seems more likely here, eh?)
- w111 (sedan most likely)
- r/c107
- ponton maybe

I guess those are the majority of the chassis we’ve got, with the exception of a bunch of w126 5.0 euro and m110 Manual and a m103.

Just beating around some ideas and seeing what the performance paddock has to say. ;-)


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W140 both good and bad ?

Specifically, what was bad about the SL wiring?


The engine bay stuff fails first due to heat, under dash wiring will second in hot climates.

Dig around a bit for the wiring insulation failure dates, I "think" it was 91 through 94. Insulation failure was not limited to MB, in 1995 I had a early 80's Volvo 760 with crumbling under hood insulation. I've also been told by a dealer parts dept that Jaguar had the same problem.

Based on your intent below, the only major wiring you need to deal with is the engine to computer harness. Upgraded harnesses are made by Delphi ( GM ). The throttle actuator insulation also fails so that will need to be replaced.

If you have a hydraulic shifted trans, the conversion shouldn't be a huge ordeal. I'd expect that at most you will need to add a road speed sensor to an axle or drive shaft. This would need to be scaled by altering tooth count / speedometer calibrator box.