w108 or w114? - Mercedes-Benz Forum

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post #1 of 17 (permalink) Old 02-13-2012, 02:37 AM Thread Starter
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Fuel injection or Carburetors?

I need some advice. Perhaps somebody here has some knowledge to share with me? I'd really appreciate it.

I'm thinking about buying either a '72 w108 or w114. I'm wondering what people find better and more reliable. Is it the mechanically fuel injected system of the '72 w108 280s with the m130 engine, or say the m114 engine of the w114 250e with its twin carbs?

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post #2 of 17 (permalink) Old 02-13-2012, 04:23 AM Thread Starter
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Sorry, that was a bad thread title choice. I really want to know what's more trouble prone. Is it the fuel injection or the twin carbs?
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post #3 of 17 (permalink) Old 02-13-2012, 04:48 AM Thread Starter
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Ok I found this old thread which was helpful:
http://www.benzworld.org/forums/vint...-mercedes.html
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post #4 of 17 (permalink) Old 02-13-2012, 04:54 AM Thread Starter
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post #5 of 17 (permalink) Old 02-13-2012, 07:16 AM
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Just my opinion, but after owning both a dual carbed six and an MFI six, I've concluded that the MFI system is better. Reliable starts and once sorted out, pretty much a low maintenance system.

I am lucky that I have the simpler Solex 34PDSI carbs instead of the notorious Zeniths. But even at that, they are a ongoing hassle. The carbs wear and leak, the heat risers stick, and they are definitely less efficient than the MFI.

By the way, a 280S has the Zenith carbs. An MFI is the 280se.

1981 300TD--310k miles
1970 280sel--172k miles
1966 230--162k miles
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post #6 of 17 (permalink) Old 02-13-2012, 06:30 PM Thread Starter
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Thanks for the info. Yeah I could see the mechanical injection being a lot less work. Reading about these Zeniths makes me nervous. I guess if they need to be tuned and synchronized one just has to pay a specialist.
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post #7 of 17 (permalink) Old 02-13-2012, 08:00 PM
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Only a fool or a master mechanic wouldn't be nervous with the Zeniths. Synchronizing them is the easy part. Understanding, diagnosing and rebuilding them is the big mental challenge. Once you take a look at an exploded diagram you will see what I mean. They also like to warp over time. Many owners just replace them with the much simpler Webers.

I was a little intimidated by the MFI when I bought the 280se, but after a little studying and tinkering it all seems so simple now. Compared to my 617 diesel there are many more inputs to the system, but it is still very understandable and has no electronics other than old-school analogue sensors and relays.

I think the best place to learn about the MFI system is the Pagoda forum.

Welcome - Mercedes Benz 230SL, 250SL, 280SL Pagoda Group

There are some very skilled mechanics there and it's a treasure of practical information on the MFI.

1981 300TD--310k miles
1970 280sel--172k miles
1966 230--162k miles
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post #8 of 17 (permalink) Old 02-14-2012, 02:25 AM
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Only a fool or a master mechanic wouldn't be nervous with the Zeniths.
Hear, hear. I'm certainly no expert, but was fortunate enough to work around MB's from a young age. My father was a zone service manager for MB (70's era) who later opened his own independent garage exclusively servicing Mercedes.

The real bottom line - either fueling system can potentially be more trouble prone, and both are hideously expensive to restore. When I acquired my '70 250 as a "fun" project, I didn't think much about "tuning up" the old Zeniths, which unfortunately had been cruelly butchered by the hands of a now defunct local radiator shop. I quickly discovered there was no solution short of completely restoring them, which took several months of my spare time, quite a bit of money and caused some serious frustration, too. (Don't try this when married, folks.) I've worked on many, many MB's, and especially enjoy diagnostic challenges on the later models - yet those Zeniths pushed me right to the edge. There are other issues on the '72 outside of just the carbs, for example, the system governing the distributor vacuum retard and advance needs to be operating correctly, or you'll never get the car running right.

When maintained, either system will provide reliable performance. In its day, the Zenith really was a fine carburetor. The 250 should instantly start in the cold weather with a pump or two of the accelerator, and run perfectly thereafter. They should stay in tune almost indefinitely. I do agree with carpenterman that MFI was the more advanced system in its day, and might be less troublesome overall. If by some miracle not now, it will still require expert care (and wads of $$$) at some point. If you are a capable "do it yourself" type, the Zeniths will require more time and less money, while the reverse holds for MFI.

If you can find one, have the cars evaluated by an oldtimer MB doc. Maybe you will be lucky, and one or the other will have seen proper maintenance, and hopefully remained relatively unmolested over the years. Much of my above mentioned nightmare with the 250 would have been avoided had the carbs not been nearly destroyed by radiator shop goons. FWIW, my father (who was factory trained on the Zeniths) always said they ran forever with little maintenance, until disturbed by someone who didn't know what the fsck they were doing. He was simply brilliant with MFI too, even on the M100.

One last remark, Webers have no place on the old six. While I can certainly understand the temptation, if you have the time and patience, the car can be made to run flawlessly with the original Zeniths - with better performance, too. (Please don't take my jab too seriously, I like the little downdraft Weber, they are inexpensive and easy to tune. Just not quite as sophisticated or satisfying to run as a good set of originals.)

Good luck!

Last edited by Leone; 02-14-2012 at 02:40 AM.
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post #9 of 17 (permalink) Old 02-14-2012, 06:36 AM
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I would choose mfi over carbs for reliability , and a w108 over a w114 for style.
I agree w carpenterman, go high tech low maintenance.
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post #10 of 17 (permalink) Old 02-15-2012, 07:19 AM Thread Starter
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Thanks for all the advice. I do want something I can drive and not be to scared of getting stranded. I don't mind complicated mechanical things. I used to work disassembling high end laptops for custom paintjobs and I never lost a part or screw. I've been repairing most things on my cars for the last 20 years. Still, I don't like annoying finicky things. The Zeniths on the w114 are in good shape and it was always serviced by the Mercedes dealership here. They're repaired a lot of things on the car and kept it in excellent shape. It was even put on display at the dealership at one point it's in that good of condition. The carbs have never been rebuilt though.

I'm also considering a turbo diesel either in a w116 or w201. Perhaps that would be less trouble. Still, a rebuilt injection pump is $1000. I think all of these cars have the ability to cost a couple thousand per year in unexpected breakdowns.

One thing I'm worried about with the w114 is finding parts if something broke while travelling. I would like to actually use the car. I'm not really one for leaving a car in a garage to collect dust.
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