Author Topic: 280SE woes  (Read 873 times)

entresz

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280SE woes
« on: 27 May 2021, 05:58 PM »
Hi all

I'm stumped by a problem with my 1975 280SE. It's a D-Jetronic euro car more specifically.

Recently it broke down. I went to accelerate onto a highway, and it coughed briefly, and then died. I eventually got it to start again - idled perfectly - but again, as soon as I went to accelerate it coughed again and died. What is frustrating is that it's an intermittent fault. I've driven it with no issues after this event, but yet again, it's happened.

I've done the following to try and remedy the problem.
- Replaced alternator - I noticed lights were dimming at idle. It now has a new alternator, and I have adjusted the idle speed up a little as it was a bit low.
- Tried bypassing the ignition amplifier. A mechanic friend of mine who inspected my car suggested this might be faulty. This was terrible as it ran even worse and stalled again only minutes after starting the car. It's definitely not this part playing up. Reconnected it again.
- New points - they were getting a bit old so replaced them
- New spark plugs
- New leads

I also have new injector trigger points (not fitted yet - yet to arrive).

It's running better but instead of completely stalling , occasionally it has a slight flat spot... not quite a misfire, but not far off. Like a hiccup, or as if your foot was taken off the throttle momentarily.

It's also notable that after it broke down, I did notice quite a lot of black soot around the exhaust.

I'm not a mechanic by any stretch but I'd like to try and get this sorted as I'm not prepared to take the car on longer trips... I don't trust it!

Does anyone else have any ideas?

I thought maybe fuel pump? but it's only a 5 or 6 year old fuel pump on it... I'd be surprised if it was already failing.

Would be grateful for any advice!
1975 Mercedes-Benz 280SE
1981 Mercedes-Benz 300D
Previous cars:
1979 Mercedes-Benz 450SE
1982 Mercedes-Benz 280E

adamb

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Re: 280SE woes
« Reply #1 on: 28 May 2021, 01:19 PM »
You seem to be really shooting far and wide on the diagnosis.

Upon reading your description of the problem my opinion was also that the number 1 suspect is the ignition amplifier. The earlier ones were weaker than the ones installed on later K-jet cars. Try to find a temporary replacement from somewhere. That should be possible in Australia.

Again, if in any doubt be sure to eliminate spark as the source of problems. It is much more likely to be the cause that the FI.

revilla

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Re: 280SE woes
« Reply #2 on: 28 May 2021, 03:17 PM »
The black soot part quickly caught my attention. That’s an indication of combustion out of balance (rich-lean). The fact that it happens suddenly and intermittently makes me think of the symptoms of a clogged (or almost clogged) filter (main, WUR, or F distributor pressure reg) throwing the mixture momentarily out of wack and then back to normal range. It’s a wild guess based on your description, but how about a batch of contaminated fuel?  (water or else). Happens to us with the small airplanes. How about draining into a container, observing and topping off again to check what happens? That’s a relatively easy thing to check.
Nothing like being next to your car to diagnose, but from far I’d bet on a fuel related issue.  Especially if the black soot gets on the ground too and especially if it’s accompanied by black smoke too (something to check out next time it happens...)
Good luck
Robert
W116 1977 280SEL & 1979 280SE

mrkozzy

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Re: 280SE woes
« Reply #3 on: 29 May 2021, 04:08 PM »
I've had the same issue for 2 years.
I knew there was something wrong but could not  pinpoint the source.
My problem was intermittent, which is the worst kind.
It's happened 4-5 times and always righted itself after a brief shutdown/cool down.
The last time earlier this year left me stranded and I had the vehicle towed home.
The picture shows what I believe was the culprit(?),
I now know it's called the Throttle Position Sensor. If you look closely you will see 1 of the 4 contact points bent  way out of place. (Cannot fathom how it got there).
I replaced the whole part, although I could've just positioned the brass contact point back from where it came, and so far the problem seems to have been fixed.

* Thanks once again to UTn_boy who helped with the clarification on this one.  ;)
« Last Edit: 31 May 2021, 02:32 AM by mrkozzy »
MrKozzy

UTn_boy

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Re: 280SE woes
« Reply #4 on: 30 May 2021, 11:02 AM »
The black soot part quickly caught my attention. That’s an indication of combustion out of balance (rich-lean). The fact that it happens suddenly and intermittently makes me think of the symptoms of a clogged (or almost clogged) filter (main, WUR, or F distributor pressure reg) throwing the mixture momentarily out of wack and then back to normal range. It’s a wild guess based on your description, but how about a batch of contaminated fuel?  (water or else). Happens to us with the small airplanes. How about draining into a container, observing and topping off again to check what happens? That’s a relatively easy thing to check.
Nothing like being next to your car to diagnose, but from far I’d bet on a fuel related issue.  Especially if the black soot gets on the ground too and especially if it’s accompanied by black smoke too (something to check out next time it happens...)
Good luck

Bear in mind he has D-Jetronic, not K-Jetronic.  So there is no WUR or fuel distributor. 

I'd be more concerned with your throttle position sensor (what MrKozzy shows) and your manifold pressure sensor, also known as the "MPS".  Rather than taking stabs in the dark, I'd start diagnosing the D-Jetronic system per the manual.  There are several online sources one can go to for D-Jetronic diagnosis directions.  Though, before doing so do make certain that the points dwell, ignition timing, and valve lash are all in good order beforehand.  And make certain that your fuel tank doesn't have trash in it clogging the fuel filter.  Don't rule out a faulty fuel pump and/or fuel pump relay, either.  Just because the pump is only 4-5 years old doesn't mean it's not bad or stopped up with trash.

Regarding the ignition module, properly known as the switch gear, it was the ones made between 1969 and early 1971 that were problematic.  Those had Germanium transistors in them that failed prematurely.  Afterward, they started using Silicone transistors, which was long lived, and is what is  in all W116 cars.  On that note, renew your ballast resistors, ignition coil, and condenser out of principle.  They are not good for the life of the car, and can cause the issues you're experiencing. 

Make sure your sparking plugs are the non resistor type. 
1966 250se coupe`, black/dark green leather
1970 600 midnight blue/parchment leather
1971 300sel 6.3, papyrus white/dark red leather
1971 280sel Black/black leather
1973 300sel 4.5, silver blue metallic/blue leather
1976 280s astral silver/blue MB Tex

revilla

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Re: 280SE woes
« Reply #5 on: 30 May 2021, 02:19 PM »
You’re right Aaron. I missed that point. I’d look into the main filter and the quality of the fuel in the tank. Although it’s still an educated guess, but a guess from far after all.
Robert
W116 1977 280SEL & 1979 280SE

BCK1963

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Re: 280SE woes
« Reply #6 on: 30 May 2021, 11:35 PM »
There is a german R107 forum which is currently hosted by a guy named Volker. His nick-name is DR. D-jet and he and a guy Christian, nick-named Obelix, is very knowledgable in that matter. He holds trainings and has written numerous technical reports on injection types and other technical topics. Most things are available in english.
Even though many of these guys tend to loose themselves in chats like how nice it was driving their R107 in nice weather last weekend, I can really recommend the technical support of Volker.



Bernd

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1974 Caddy CdV   since 1992  (for sale)

mrkozzy

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Re: 280SE woes
« Reply #7 on: 31 May 2021, 02:50 AM »
UTn_boy.  Further to your comment;

"On that note, renew your ballast resistors, ignition coil, and condenser out of principle.  They are not good for the life of the car, and can cause the issues you're experiencing."

I'm very interested in your knowledge about replacing these bits. Whilst my car runs very well, I still feel its only around 90%. I still have lots of cranks b4 it starts and the occasional hiccup at highway speeds.
Nothing I lose sleep over, but we like to strive for perfection, don't we?  ::)

My ballast resistors are original.  Have some used ones in a box I've scavenged off wrecks over the years. Should I use them or go for "new"
My ignition coil seems to be working fine. It was however changed some 25 years ago.  Replace with new?
Which condenser are you referring to? 

Or leave well enough alone?
 cheers  Kozzy
 
MrKozzy

UTn_boy

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Re: 280SE woes
« Reply #8 on: 01 June 2021, 09:06 AM »
UTn_boy.  Further to your comment;

"On that note, renew your ballast resistors, ignition coil, and condenser out of principle.  They are not good for the life of the car, and can cause the issues you're experiencing."

I'm very interested in your knowledge about replacing these bits. Whilst my car runs very well, I still feel its only around 90%. I still have lots of cranks b4 it starts and the occasional hiccup at highway speeds.
Nothing I lose sleep over, but we like to strive for perfection, don't we?  ::)

My ballast resistors are original.  Have some used ones in a box I've scavenged off wrecks over the years. Should I use them or go for "new"
My ignition coil seems to be working fine. It was however changed some 25 years ago.  Replace with new?
Which condenser are you referring to? 

Or leave well enough alone?
 cheers  Kozzy
 

Let me ask you these questions

....Have you watched the function of your coil on an oscilloscope while under electrical load at varying RPM's, and compared the results to hot and cold? 
-Have you measured the resistance of the ballast resistors when they're cold AND hot?  It should not change by more than .2 ohms at the most.
-Do you have non resistor plugs in the engine?
-How old are your plug wires, and what is the resistance of the wire and supressor end separately, when cold and when hot? 
-What does the spark pattern look like on each cylinder on the oscilloscope?  If there is a variance, how much is it?


Whether lightly used or heavily used, 25 years is a long time for a coil.  And no, one does not put used ignition components on their car unless it's temporary or in an emergency.  It's like putting a used headlight bulb in......it may last two days or two years. 

The lots of cranks before starting....is that when hot or cold, or both? 

The condenser.....the one in the distributor that controls the voltage spikes in the points so they don't prematurely burn up.  To my knowledge, there is only one condenser in the M-116 and M-117 v-8 ignition systems.  Do you have more than one for some reason? 
1966 250se coupe`, black/dark green leather
1970 600 midnight blue/parchment leather
1971 300sel 6.3, papyrus white/dark red leather
1971 280sel Black/black leather
1973 300sel 4.5, silver blue metallic/blue leather
1976 280s astral silver/blue MB Tex

entresz

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Re: 280SE woes
« Reply #9 on: 02 June 2021, 11:52 PM »
Thanks for the replies everyone
It's really helpful
There are few more things for me to check

I'll also try and get in touch with Volker -- I have read some of his articles - they're VERY informative

When I bought the car - original owner provided me with some parts... I think I might actually have a throttle position switch there. I'll check.

I'll also put some fresh fuel in and see if that helps. Would be good if that was all the problem is.

These intermittent faults are very frustrating but I shouldn't complain as it's been very reliable until now.

« Last Edit: 03 June 2021, 09:03 PM by entresz »
1975 Mercedes-Benz 280SE
1981 Mercedes-Benz 300D
Previous cars:
1979 Mercedes-Benz 450SE
1982 Mercedes-Benz 280E

BCDC

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Re: 280SE woes
« Reply #10 on: 03 June 2021, 06:08 PM »
This is very interesting. Thanks to everyone and especially Utn boy who's "guru" status in my book is well deserved. My 1978 280SE although runs and drives very well, sometimes has a slight miss at idle when hot. I will now check and replace ballast resistors, coil and plug leads. This forum always is so helpful for these absolutely wonderful cars. Thanks again everyone.

BCDC

Solar power can save this planet.
1978 280SE Cream with blue interior. With SLS

entresz

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Re: 280SE woes
« Reply #11 on: 03 June 2021, 09:04 PM »
This is very interesting. Thanks to everyone and especially Utn boy who's "guru" status in my book is well deserved. My 1978 280SE although runs and drives very well, sometimes has a slight miss at idle when hot. I will now check and replace ballast resistors, coil and plug leads. This forum always is so helpful for these absolutely wonderful cars. Thanks again everyone.

BCDC

Solar power can save this planet.

Hi BCDC
Is there any chance it was you that I drove past near Mary's Hope Road in Hobart a maybe six months back? I was in my silver 280SE.
It's so rare to see another one, especially in the same colour on the road!
1975 Mercedes-Benz 280SE
1981 Mercedes-Benz 300D
Previous cars:
1979 Mercedes-Benz 450SE
1982 Mercedes-Benz 280E

BCDC

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Re: 280SE woes
« Reply #12 on: 05 June 2021, 05:40 PM »
Hi entresz, I don't think I was driving in that area at that time, so probably not me. Mine is pastel grey but it looks like off white or cream in the sun. It's interesting not to see many in Hobart as there seems to be plenty here in Cygnet, 2 white ones plus mine, a champagne metallic one and a gorgeous R107 450 SL fully restored, not a W116 but worth a mention. I know one local fella who uses his as a daily driver and we chat often in the main street. His had done almost 300K and still runs like a dream. Mine only 97,000 so only just run in. I have seen others while driving mine too in Tasmania, so maybe the climate is conducive to the longevity of these cars. I even saw  a silver one during last summer towing a trailer heading towards Kettering!

BCDC
1978 280SE Cream with blue interior. With SLS

entresz

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Re: 280SE woes
« Reply #13 on: 06 June 2021, 06:58 PM »
Hi BDCD
Oh -thought your car was silver like mine from the avatar! that sounds like a really interesting colour -never seen one in that shade before.
I've seen a couple nice Mercedes out Cygnet way. One notable one was a green 300D with over 700 000kms! I couldn't believe it!

I think the cooler and fairly dry climate of Tassie is good on old cars. The only bad thing climate-wise here is the hot sun and the strong UV. That is hard on the paint and interiors.

That's incredibly low mileage on your car. mine has done 195 000, I thought that was low haha! By all accounts these cars are incredibly long lasting and can rack up some very impressive mileage. I have no reason to doubt that, despite mine mis-behaving at present  ::)
1975 Mercedes-Benz 280SE
1981 Mercedes-Benz 300D
Previous cars:
1979 Mercedes-Benz 450SE
1982 Mercedes-Benz 280E

BCDC

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Re: 280SE woes
« Reply #14 on: 06 June 2021, 09:25 PM »
Hi entresz, I know the guy who had the very high milage 300D, he has since retired it and has a W124 diesel. 

A bit more of the story of my W116. It was originally delivered to Papua New Guinea for use by the governor in late 1978, it still has some of the rego stickers on the back window. Then after "it" was retired from duty there, bought by a fellow on the gold coast for a while, all the servicing is documented in the books, then somehow sold to a person in Launceston Tasmania who kept it garaged apart from the occasional drive to the shops stc, hence the low KM's on the clock This owner had it for over 20 years then when too old to drive he sold it to a woman in Hobart to pick people up from the airport to do wine tourism but it didn't suit her well enough so she put it up for sale and that is when I bought it. Whew, a bit of a story but interesting that the history has been noted in the books. I'm slowly restoring all the bits that wear out on a 40 plus year old Mercedes like all the rubber parts etc. The old girl is in very good condition apart from a cracked dash from all the sun up there in the tropics I suppose. It purrs like a kitten and goes like a panther.

BC
1978 280SE Cream with blue interior. With SLS