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sluggish 450SE

Started by larrud, 03 August 2020, 07:54 PM

How can I get my Benz to run better?

fuel injection upgrade
0 (0%)
revised tuning
0 (0%)

Total Members Voted: 0

larrud

Hi - this is my first post here, so please forgive me if I don't know all the rules yet. I've got a 1973 450SE that has undergone a full mechanical restoration as well as a complete interior refurbishment. It's a one owner car out of California it's whole life and has 60k miles. Car is tight as a drum and drives like a train. Here's the problem. It runs like crap. It's slow, drinks gas like a drunk, and has an annoying hiccup when pulling away from a stop. My "expert" vintage MB mechanic says there's nothing further he can do, but I cannot accept that, considering how many W116 owners love the way their cars drive. I'm in SW Florida and there are not a lot of vintage MB specialists down here. I've put a ton of money into this car and I'd like it to drive like it looks and feels. Does anyone  out there have suggestions based on similar experiences? Any vintage mechanics with advice? I would even ship the car someplace if necessary. Hope somebody can help. Thanks.

raueda1

This could be sooooooo many things.  A "vintage" MB mechanic who throws up his hands is no mechanic IMO.  You need somebody who can rigorously evaluate and correct the fuel injection and timing.  Maybe more, but that's a start.  Does the car have D-jetronic (probably) or K-jetroinc?  And are you looking for a mechanic or doing it yourself?
-Dave
Now:  1976 6.9 Euro, 2015 GL550
Before that:  1966 230S, 1964 220SE coupe, 1977 Carrera 3.0

revilla

So many possibilities indeed.
But from your description timing and/or fuel mixture come to mind. Both are relatively easy to adjust for a broad test of the situation. Fine tuning will come later.  Another quick and easy thing to check are the spark plugs and their cables.  Or a clogged fuel filter.  But before we continue "guessing", Dave's questions are key. Also do you have tools like a stroboscopic lamp to adjust ignt timing? If not, Autozone stores or other can certainly lend you one.
Let us know.

larrud

My "vintage" MB mechanic has a very good reputation but I think he's just tired of messing with my car. I bought this car on Bring a Trailer and, quite frankly, I got taken. Everything was wrong with the car and it had been sitting in storage for 10 years. He fixed "everything" and now we're down to this last, but all important item. The car does has D Jetronic. All items such as plugs, cables, points, injectors were replaced. I used to be a DIY'er but that was a looooong time ago on American iron. I no longer have the time or knowledge for this and am looking for someone who is willing to take the time to pore over every aspect of this vehicle. My mechanic has many customers with much later "plug and play" vehicles and bottomless checkbooks, so I can see why he's tired of me. I'm very picky and my expectations are perfection, but I am willing to pay for it. I'm just at a dead end in the road right now. I'm in SW Florida and he's the only guy within 100 miles who does this kind of work. Right now, the car just sits because it's not enjoyable to drive. I'd ship it someone who wouldn't try but guarantee to get it right.

Thanks for the feedback.

daantjie

Here is a link to some good tips on both DJET and KJET.  Overall I much prefer the KJET system, it is much more robust and parts are much cheaper and readily available for it:

https://www.benzworld.org/threads/bosch-d-jetronic-and-k-jetronic-troubleshooting.1223523/

Member "sclass" has a lot of DJET knowledge as I recall, plus other knowledgable folks on here.  Just fair warning though that you might have to taper your expectaion of perfection a bit, these are almost 50 year old cars after all ;)
Daniel
1977 450 SEL 6.9 - Astralsilber

larrud

Wow! That's an amazing amount of information to digest. I wonder if my mechanic performed all those, if he should, on a 47 year old car that has been sitting for 10 years. He did tell me that he thought he could do more with a K Jet than the D, particularly because it took forever to find a set of injectors. But, swapping over was very expensive and we would have to obtain a used unit and deal with that. He didn't think it would perform any better, nor get better mileage, at which point I thought I'd stay with the "devil I know".

You're right, I shouldn't expect "perfection" but, after reading so many people's comments on how their cars perform, I'm sure something's missing here.

rumb

I think you are going to have to get on the phone and call a lot of independent mb mechanics in your area until you find one that knows d jet. They are certainly getting hard to find.

Benzworld forum has a section listing mechanics by region.
'68 250S
'77 6.9 Euro
'91 300SE,
'98 SL500
'14 CLS550,
'16 AMG GTS
'21 E450 Cabrio

raueda1

Quote from: larrud on 05 August 2020, 12:54 PM
Wow! That's an amazing amount of information to digest. I wonder if my mechanic performed all those, if he should, on a 47 year old car that has been sitting for 10 years. He did tell me that he thought he could do more with a K Jet than the D, particularly because it took forever to find a set of injectors. But, swapping over was very expensive and we would have to obtain a used unit and deal with that. He didn't think it would perform any better, nor get better mileage, at which point I thought I'd stay with the "devil I know".

You're right, I shouldn't expect "perfection" but, after reading so many people's comments on how their cars perform, I'm sure something's missing here.
And that is exactly the point.  There are zillions of posts here on reanimating cars that have been sitting forever.  Maybe start searching 'barn finds' and the like on this site.  All the must-fix-after-sitting possibilities have been beaten to death somebody.  The rabbit hole suction is strong with this one....    ;D
-Dave
Now:  1976 6.9 Euro, 2015 GL550
Before that:  1966 230S, 1964 220SE coupe, 1977 Carrera 3.0

Randys01

So yours is an early D jet. Be assured  ordinarily, D jets sparkle so there is something definitely wrong with your bus.
Forget any notion of swapping to K jet.
So it wallops the gas but does it look obviously rich  {black/grey smoke} out the exhaust?.when hot..under load?
Does it run like the village idiot when cold and warming up?
If yes to all of the above you can be reasonably certain that the enrichening mechanism in the fuel injection is out of whack....rather than individual injectors.
I'm not full bottle on D Jetronic but as a first principle, I'd be concentrating on the device that measures the air flow and sets the mixture accordingly. These days they call them Mass Air flow meters but the D runs a rudimentary form.
Before lurching into this  just make sure your valve timing is correct. So many major rebuilds end up with a cam sprocket  a tooth out. It will run but it will be cranky. Also ensure ignition timing is correct. It's amazing how far out this can be after major reassembly and the thing will still run.
You must eliminate these seemingly unlikely issues first as they cost nothing but once ticked, you know you have to dwell on the fuel management.