I have just bought a W123 280E as a parts car. It has a little cosmetic rust, good A/C, paint, seats, sheepskins, rubber and all are fine.

Here is my problem:
The 280E engine starts easily, but will not run below around 1500 RPM (by ear) and it misses badly at that speed. I haven't tried it on the road yet (slip into D at 1500 rpm??)
I have searched on the Tech Forum and although I found it has the M110 engine, I haven't found a diagnosis of my problem.
I also read that they have valve guide and head issues and require regular valve adjustments.

If any of you have this engine fitted to any of your cars, or have experience with this model, and can assist me, I am open to suggestions.
I will be towing it home tomorrow night and will be able to test compression, vacuum etc then.
Thanks in Advance.
ps, Photos to come.

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Tony from West Oz.
Fatmobile 3 84 300D 295kkm Silver grey/Blue int. 2 tank WVO - Recipient of TurboDesel engine.
Josephine '82 300D 390kkm White/Palamino int.
Elizabeth '81 280E, sporting a '79 300D engine.
Lucille '87 W124 300D non-turbo 6 cylinder OM603, Pearl Grey with light grey interior


Various parts cars including 280E, 230C & 300D in various states of disassembly.

let me know if you decide to part this one out...

i still want that wood finished climate control panel i am assuming most of youalls w123s(wrongly?)

I had a 79 280S with 300 000 K's on it when I bought it. The valve stem seals were shot and probably the guides as well etc, but I drove it for 80 000 more K's like that and it ran great. Never heard of any head problems with these motors. They are some of the best Mercedes ever made. Mine had the awfull carbureattor though and I cant comment on the "E"s fuel injection system.

- Peter.

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2021 Chevrolet Spark
Formerly...
2000 GMC Sonoma
1981 240D 4spd stick. 347000 miles. Deceased Feb 14 2021
2002 Kia Rio. Worst crap on four wheels
1981 240D 4spd stick. 389000 miles.
1984 123 200
1979 116 280S
1972 Cadillac Sedan DeVille
1971 108 280S

If it is a carborated version wonder if dried gas residue is in the idle passages etc. If you remove an idle jet and it is low on the carb gas should come out. If not filling the fuel bowl up with laquer thinner will disolve the residue. Just watch for resumption of flow from idle passage. Has worked for me and somewhat easier than kitting carb. I just put fuel line in laquer thinner can and let engine run till carb is saturated. Turn engine off and let carb soak.Also car runs well on the thinner itself. If the car sat a long time unused it is a possibility.

engines are pretty bulletproof. about as reliable and durable as a diesel. a little more to go wrong but not much for a gas engine especially of that vintage. it is fuel injected but no computers.

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

I have the car at home. I drove it all of the way and only stalled it once, just checking to see if it would idle at all. Obviously not.
I was able to keep the engine running with judicious throttle application and slipping into neutral while rolling to a halt at traffic lights (not many I know the back roads here well).
While driving at 50 MPH, the engine pulls well (I am used to a non-turbo 300D remember) and tranny kicks down to 3rd on full throttle.
Below 40 MPH, there is an intermittent miss and backfire thru the aircleaner at neutral throttle.
From a standing start, I can have the engine at 1500 RPM (irregular firing) and slip it into D. The engine RPMs drop, but with slightly more throttle application it pulls away well without any obvious miss. I am not talking WOT acceleration.

I tried WOT acceleration as well and the car moved out well, although with that engine I thought I would have some loss of traction.
Tranny shifted well, up and down the gears, although I didn't check 3-2-1 while stopping, as I was in neutral nursing the throttle.

Possibilities:
1. Burnt valve (s) or other compression issues
2. Fuel injection issues - pump, injectors, etc
3. Spark issues - dizzy cap replaced by mobile mechanic for PO with no changes to symptoms. Do these engines have electronic ignition?
4. Anything else??

I will pull the plugs to determine which cylinder is not firing well, and do compression test on each pot while plugs are out.

Can anyone help me with diagnostic tips for the fuel injection?

Thanks,
Tony

__________________
Tony from West Oz.
Fatmobile 3 84 300D 295kkm Silver grey/Blue int. 2 tank WVO - Recipient of TurboDesel engine.
Josephine '82 300D 390kkm White/Palamino int.
Elizabeth '81 280E, sporting a '79 300D engine.
Lucille '87 W124 300D non-turbo 6 cylinder OM603, Pearl Grey with light grey interior


Various parts cars including 280E, 230C & 300D in various states of disassembly.

I would be willing to bet a US dollar against an Australian dollar that the problem is a vacuum leak somewhere. It might be in an obscure, hard to find location, but I'll bet that's the problem.

Best of luck,

If he does, you will need to drive over and pick the parts up, yourself.

Are you saying that the SI engines have vacuum issues too?
I thought MB saved those for us diesel heads.
does the mechanoical fuel injection on these (K Jetronic ??) have vacuum controls?

iNeon, the car is a W123, but has black plastic console and manual HVAC controls. Zebrano strip across width of dash only.
You are welcome to "drive over" for a look. Just make sure you take a deep breath as you leave California It will be a long way before your next opportunity.

As said before I will try to whip the plugs out tomorrow night.
Thanks All, keep the ideas flowing.

__________________
Tony from West Oz.
Fatmobile 3 84 300D 295kkm Silver grey/Blue int. 2 tank WVO - Recipient of TurboDesel engine.
Josephine '82 300D 390kkm White/Palamino int.
Elizabeth '81 280E, sporting a '79 300D engine.
Lucille '87 W124 300D non-turbo 6 cylinder OM603, Pearl Grey with light grey interior


Various parts cars including 280E, 230C & 300D in various states of disassembly.

Tony,

ANY gas engine can have vacuum issues. Vacuum leaks can be anywhere past the throttle plates on a gas engine. This could be a rotted vacuum supply hose, a leaky intake manifold gasket, a leaky carb or throttle body flange gasket, an egr valve, etc.

Hook up a vac gauge and start the engine and lower the RPM while watching the vac gauge. If the vac drops significantly while the RPM are coming down then you have a vac leak. When you are at higher RPM, the volume of air being drawn can overcome the vac leak.

If I were you I would start an ALL OUT search for anything that might be leaking vacuum. A visual inspection might very well find the culprit. If not, you can use a length of hose about 1/4" inside diameter with one end in your ear and using the other end to probe around everywhere at joints and hose connections and listen for a hissing sound. Also you can squirt oil around things like the carb base and such things to see if it will momentarily seal it up and cause the engine to smooth out momentarily.

You can also find vacuum lines that connect accessories inside the car, disconnect from the engine and plug on the engine side to see if that is the source of the leak.

My bet offer is still in place. I really, strongly believe that you have a vacuum leak of some description.

In fact, since it's Winter there and I'm broiling in 100 degree heat, send me a plane ticket and I'll come and help.

Best of luck with it,

are worth a check too. by all means do a compression test too. but the vacuum runs the distributor advance. if the hvac is manual then the only other vac system that leaps to mind is the door locks. plenty of places to leak.

__________________
[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

If it were bad spark plug wires the effect would be the opposite. The engine would idle but not make power at higher speed under load.

Have a great day,

i might just decide to pick one up if i ever travel abroad!

i really like those wood trimmed air conditioning controls(the manual ones) i dont want the headache of old technology just the simple elegance of 3 rotary knobs. why cant car companies stop fiddling with stuff like this?

the neon has arguably(of course) the best ventilation controls on any car ive ever been in. it has 17 different settings. if you want a smidge of ac on your face and most on the floor, it can be done. it really helps in the hot, humid alabama summers to not turn down the fan but divert the air in a customizable way. i hate cars that the a/c only comes out of the vents, hate them!

so im not being a butthead, good luck with the car, ive never even seen a gas w123 in person!

i agree with larry, it sounds more like vacuum. i was just adding a thought.

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

As this is a non US vehicle it's possible the headlight adjustment is also vacume. It was on my 83 200 in South Africa. In addition to the door locks the fuel filler door could also be vacume. Was on my 79 116 280S, was not on my 200, but a 280E was a a higher spec than the 200 so it might have one.

I'd like to see some pic's if you can some time. Those m110 engines didn't have the power of the V8's but they were magnificent high speed cruisers. If it were me and I had the money, Id probably be quite happy to do a complete top end overhaul if necessary, and if the overall condition of the car warrented it.

- Peter.

__________________
2021 Chevrolet Spark
Formerly...
2000 GMC Sonoma
1981 240D 4spd stick. 347000 miles. Deceased Feb 14 2021
2002 Kia Rio. Worst crap on four wheels
1981 240D 4spd stick. 389000 miles.
1984 123 200
1979 116 280S
1972 Cadillac Sedan DeVille
1971 108 280S