Mercedes W114 250 Coupe - help!

[Druk]

Swapped the seeyoujimmy hat for something more seasonal perhaps?

Engine number hopefully on the V5C beneath the chassis Vin maybe beginning 'M' or possibly 129---------


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[Charles Morgan]

The C U Jimmy hat is excessively festive. Right now I put on my best fingerless gloves and go around wishing people a merry Bah Humbug.

No V5C!

Complicated story, but the car has no paperwork at all.

 

[Druk]

Chassis number will suffice.

edit. Manual indicates engine number should be on plate itro cyl 5-6 right side rear of engine (as seen from front).






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[Charles Morgan]

It will have to be chassis number. The nearside of the car is currently underneath his model railway and bonnet opening is limited to about a foot. I suspect a request to dismantle a four track mainline station with sidings and signal box is unlikely to meet with an entirely positive response.

The engine should be an M114 2.5l 6 cylinder with Bosch D Jetronic. I suspect any tuning manual suggestion would be limited to "Replace with something bigger".

 

[Druk]

PM suitable postal address. Manual covers M114 and is letterbox size 7" x 10" x 1".

Post pics of model railway. Much more interesting than old cars.




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[Charles Morgan]

Thanks for the book Druk, it arrived this morning!

Lots of space has been freed up in the garage so I'll start shifting chrome over on Monday.

 

[grober]

DJetronic Fundamentals
and this is an informative thread on troubleshooting
http://forum.w116.org/mechanicals/d-jet-vs-k-jet/

 

[Charles Morgan]

Whisper it quietly but muggins had a D Jetronic system on his Citroen SM which has been switched to Megasquirt ECU with modern sensors, injectors and a bespoke map. This is the most likely, probably only, mod muggins is thinking about.

 

[Charles Morgan]

The plan, such as it is.

With all plans it is defining what A and B are before drawing up the means of getting from A to B. So the first thing is to establish what the real state of the car is (A) and to define what result I want for the car (B). Needless to say, A may well change as the work starts, as might B, so keeping options open is essential. Keeping costs down is also vital - these cars are not hot property and I think that is unlikely to change. This rules out engine changes or similar.

B I doubt will change that much. I want a nice old Benz, clean and tidy but not pristine, which will happily take me on a nice wine tour in France or a classic car rally. So reliable, brisk, comfortable and economical. Stance is about the only mod I can think of, but that can be left for a long way ahead.

For the reliable, brisk and economical bit, the 250 is OK - in original tune it produces 150 horses which in my experience is the right side of stately and the wrong side of brisk, so may need just a little pepping up. The results of switching my Citroen SM from D Jetronic to Megasquirt ECU etc have been revelatory - a really singing, flexible, much more economical (well over 60% better) and starts on button every time reliable car. I have no idea if the engine is generating more horses, but it wouldn't surprise me. The great thing about the switch is that no real engine work needs doing - just installing sensors and injectors. About the only thing that might need engine out is fitting a CPS - the SM had a drilled flywheel, but reading up, it might be possible to use the pulse from the electronic dizzy. More work required.

So first stage after getting it here is clean, label and store trim. List parts required, and see what needs to be done to get the engine running.

Right, now it's no longer raining outside, time to finish off the garage. This would have been done yesterday but Mocas turned up to have a run in my Fiat 127 before I sell it, which meant a lot of tea and cake and jawing rather than clearing.

 

[guydewdney]

About the only thing that might need engine out is fitting a CPS - the SM had a drilled flywheel, but reading up, it might be possible to use the pulse from the electronic dizzy.

If its the same as my 280CE setup, there is a CPS already which is connected to the diagnostic (hahhaha) socket for, I believe s 'computer' called a Herman? Theres a small 20mm? diameter socket near the front of the engine? The CPS is on a shielded cable from this.

 

[John Jones Jr]

Fit a trigger wheel & sensor to the crank pulley, no need to remove the engine.

 

[grober]

If "HERMAN" doesn't exist then another accessible solution might be a toothed wheel and sensor bolted to the front of the crank'pulley . Several aftermarket ignition suppliers offer this- probably Megasquirt does also
e.g. Electromotives XDi high resolution, 60-minus-2 tooth crank trigger wheel. This affords resolution unheard of in any other electronic ignition available today, offering spark accuracy of ¼ degree of crankshaft rotation. This accuracy makes the system ideal for the most demanding engines. That's what that guy put on the ESPADA engine eXtreme Direct Ignition System (XDI) | Electromotive

John Jones Jnr beat me to it!

 

[grober]

How to use DIYAutotune.Com's crank triggers

 

[bolide]

Personally I'd use that high-tech system called "Twin Webers". Or go one better and use Triple carbs!

Nick Froome

 

[219]

The plan, such as it is.

... I want a nice old Benz, clean and tidy but not pristine, which will happily take me on a nice wine tour in France or a classic car rally. So reliable, brisk, comfortable and economical. Stance is about the only mod I can think of, but that can be left for a long way ahead.

For the reliable, brisk and economical bit, the 250 is OK - in original tune it produces 150 horses which in my experience is the right side of stately and the wrong side of brisk, so may need just a little pepping up. The results of switching my Citroen SM from D Jetronic to Megasquirt ECU etc have been revelatory - a really singing, flexible, much more economical (well over 60% better) and starts on button every time reliable car. I have no idea if the engine is generating more horses, but it wouldn't surprise me. The great thing about the switch is that no real engine work needs doing - just installing sensors and injectors. About the only thing that might need engine out is fitting a CPS - the SM had a drilled flywheel, but reading up, it might be possible to use the pulse from the electronic dizzy. More work required.

There is no doubt that the 250 coupe is a lovely , charming old car .

Despite what the figures in any books say , I'm sorry to say that I don't think that in the real world it will be all that economical .

I remember these cars from back in the day and , while the 250 is certainly a refined and pleasant cruiser , it isn't going to set the road on fire . A friend had one and I remember it being a thirsty beast , about on a par with my 280E which hovered at sub 20 mpg and you had to drive with a light foot to get into the low 20's .

My 220/8 was a bit better , returning mid to high 20's and , with gentle driving , could be coaxed into the low 30's .

Admittedly , my 220/8 and the 280E were both manual , so had the potential for better economy ( although my 280 with 5 speed close ratio box tended to be driven with 'enthusiasm' most of the time , so refuelling every 200 odd miles was the norm - thankfully petrol was cheap back then ) . My friend's automatic 250 saloon was probably at a disadvantage , economy wise , but I know he moaned a bit about its thirst . It was comparatively economical against another friend's W108 280SE which he reckoned got about 10-12 mpg in the real world ( mostly town driving ) though .

Perhaps your megasquirt conversion ( and maybe look at fitting a 123 electronic distributor ) will make a difference . LPG conversion may be worth looking at too ? That is , if you are thinking of doing high mileage in it - otherwise you have to weigh up the conversion cost against fuel savings ; if only doing 5000 miles pa , perhaps cheaper to just put up with poorer fuel economy .

Otherwise , you could always speak to the nice Mr Rhind about a diesel conversion - while the saloons came as Diesels the coupes never did , but not to say it couldn't be done .

Certainly , back when they were current , these were very pleasant and reliable cars to drive around in - I put close to a quarter of a million miles on my 280E with only two mishaps : once the gear lever came out in my hand going across a roundabout , leaving me with no gears until I was able to reinsert it ; the other time was failure of the electronic ignition module on the nearside inner wing . Not counting consumables like brakes , clutches , exhausts , tyres etc .

 

[219]

Personally I'd use that high-tech system called "Twin Webers". Or go one better and use Triple carbs!

Nick Froome

Of course , the 250 was available with large , complicated and unreliable Solex carbs too .

 

[Charles Morgan]

I've had a car (a converted BMW 2002tii) with a sensor mounted to run off the crank - it was a disaster, the bracket holding the sensor on cracked on two occasions (hello hard shoulder from overtaking lane at speed), and then a forged one was fitted which lasted a bit longer, until that one went. That car broke down some 6 times in my ownership, all bar one were caused by the mods being done badly - the one that did was the workshop forgot to re-connect the alternator to the battery after refitting the sensor! The Dutch guy who did my SM started with the same route on his experiment, had similar issues, so decided if you are going to fit a sensor, do it where the manufacturers do - the flywheel.

Webers appeal, but not for real life.

Derek, when I did the SM I have so far had about 60% better economy and that is with a really heavy right foot (listening to a revving Maserati V6 in tune is quite a lot of fun) and I suspect I'll do reasonably well with this. With a good map and modern injectors you are running at a really efficient AFR all the time.

 

[Charles Morgan]

Just to show how civilised this all is, I popped over at 10 this morning to say I would bring the car round to load all the trim in tomorrow. 2 hours later I returned bearing large slices of freshly baked fruit cake (with loads of yummy almonds) and lemon drizzle car. The former is now being enjoyed with a nice mug of tea, it has obviously been given a slug of decent whisky too.

Bliss...

 

[Charles Morgan]

Personally I'd use that high-tech system called "Twin Webers". Or go one better and use Triple carbs!

Nick Froome

Hooligan...

 

[219]

Oh , in case you haven't seen it before , here is a link to the 123 electronic distributor for that car

123ignition electronic ignition systems for classic cars