I currently have a 1973 250 CE in for repairs it has a W114 engine and I am unable to find any service manuals for this particular car. It has a Bosch Electronic Fuel Injection System as standard and I can find no reference to this EFI system anywhere.

When it arrived I was told that the battery was faulty and as this is a show car that was not hard to believe. I could then start the car but after fitting a new battery it got worse still until I'm currently at the stage of only being able to keep the motor running for a few seconds.

I'm sure it is an electrical problem and something to do with a relay for the fuel system but as I can find no technical details at all about this particular setup I do not know what relays do what. To make matters worse I am unable to locate any mechanics who have detailed knowledge of this type of setup. The general layout of the car is normal but the EFI system is totally different to the latter models.

Can anyone advise me where I can obtain any technical data on this car or a service manual that covers the fitted Bosch EFI system and a wiring Digram? Even the actual model of the Bosh Fuel Injection system would be of help as I could then get the proper Bosch manual.

Of course all the normal channels for service manuals insist that this car should have Carbs or Mechanical Fuel Injection but Mercedes insists that it is as original with the EFI but are unable to tell me the model of the EFI system.

Col

The system is D-jet. The "D" stands for druck, pressure in German. The system is basically the same as used on the earliest V8s. There will be trigger points in the base of the distributor that fire injectors in groups of three. Volvo 164e had similar system and maybe the same points. There also was a BMW that used the system (also very rare). The Volvo is the common 6cyl version, although if you need trigger points the four cyl versions used in VW, Volvo, and 914 Porsche 1.7 and 2.0l may be a fit.

Since you refered to the battery a good place to start is the positive battery cable. In all the MB versions the main power lead was attached to the positive lead. The wire was not incorporated into the cars wiring harness and if you follow it, it will lead you to the EFI relay (controller relay). Once powered up the fuel pump ran for 1 sec and died unless the car was cranked.

The injectors are feed side controlled unlike modern injectors that are controlled on the ground side. A most usefull characteristic is the operation of the acceleration enrichment system built into thye throttle switch. If you turn the car on with the engine off and move the throttle to full throttle slowly you will hear the group of injectors, currently engaged by the trigger points, fire twenty times. This is always the first step to see if the controller is functioning. It also can be used to verify the trigger points, somewhat.

The points often get stiff with time and don't close fast enough to reopen the next go round. Sort of like floating valves.

__________________
Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician

This is a Euro spec car. D-jet was not used in the US, although it might have been in Canada, that's why you get the info you get. No mechanical injection in the W114 chassis, either.

Fuel pump should run about 1 sec when ignition switched on and when starter is engaged or engine running. Fuel injectors must click when cranking even if it doesn't start.

Sounds to me like it's running on the cold start valve only -- fires, dies, does it again for a while, then eventually won't even sputter -- let is sit a while and it will again start briefly. That means no injection.

You can test the trigger points with an ohmeter if you pull the dizzy -- which I would on principle to clean the trigger points with brake parts cleaner. Make sure whatever you use doesn't contain methylene chloride or it will melt the plastic covers on the points and possibly the rubbing blocks, too! Flush out all the oil and verify that the points make contact as the dizzy turns. the oil will prevent them opening and closing cold, no effect hot. Worn rubbing blocks will require new points.

Another spot to check is the ground for the injectors and control box -- not sure where it is on the W114 chassis, but it's on the right side firewall on the W108. Big nest of brown wires, and if the connection is corroded, no injection.

If the car hasn't been driven for quite a while, drain some gas and check condition -- if it reeks of stale gas, drain it all out and replace with fresh and jumper the fuel pump relay (can't tell you the location unless it's on the ECU bracket, in which case it will be the bottom relay) and let it run a while to flush all the goo out. With any luck, it will run then.

Pete

__________________
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!

After much mucking around it turned out to the the engine management module but the injectors where opening and being triggered but only at cranking speeds anything greater and it was just running on the cold start injector.

Of course after testing the injectors where actually opening I then resorted to basic electrical things like ignition switch, points and replacing the injector points in the distributer all to no avail. If I shorted out the fuel pump relay it would at least idle as long as I wanted it to but of course it wouldn't come off the idle and certainly was underivable. My best guess is that the owner jump started this car and damaged the control unit. Now that it is drivable all I have to do is build a new Transistorized Ignition Module and clean up the mess that I've made.

But thanks for the data as I will certainly get a Bosch Manual for the Injection system which is so much like the latter units but has different relay points. What I found confusing at first was the lack of any transistorized ignition module but on closer inspection I found it hidden between the battery holder and the front of the car. Incidental the car was an AU delivered unit so that is probably why there is so little data about it.

Thanks

Col Luck

Certainly sounds like fouled trigger points -- if the electronic fuel injection computer operates the injectors at idle, it should also operate at speed, transistors are usually either bad or not, no intermediate conditions!

Pull the trigger points if you haven't and examine them. Might be hard to get new ones (or expensive), but it sounds as if they are not working.

Also check the play on the distributor shaft bushings -- if there considerable wear, the shaft may be pushing over so far that the points don't open and close!

The engine rpm data is provided by the trigger points, so if they won't work above idle, the fuel pump will shut off.....

Peter

__________________
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!

The trigger points where one of the first things that I changed as I've had problems with them previously. I then changed the electronic part of the ignition switch as I was unsure that it was working properly I've also had a few of those go west over the years although I've only had to replace 2 from a Mercedes.

The whole thing was beginning to get to me as while the injection system is not one of those "Black Arts" to me this one just is different and without a wiring diagram I was unsure exactly what relay did what. Add to that there are 3 relays connected that actually fed nothing other than a wire that ended in a spade connector and a few other minor things like about half a mile of wiring that did absolutely nothing and has since been removed. Then the fact that there was a Kettering Ignition system fitted was more that a bit confusing. I eventually found the Transistorized Ignition Module well hidden in front of the battery tray and about half a inch away from the front of the car so it started to begin to make more sense even though I could not find any wires exiting from the loom that should have feed the coil with the trigger impulses and there where certainly none cut off. Short of removing all the loom covering it will be almost in possible to find where the wire has disappeared to. Also there is no power getting to the Ignition Module and I can not find where it has been disconnected so my original feeling was that something had gone wrong with the ignition switch particular as there is a heavy weight hanging off the key ring.

But just to make matters even better all the low pressure power steering hoses had been replaced with water hose which was in the process of dissolving and spreading hot ATF all over the engine bay. It was anything but clean and not at all what I had expected from the previous times I've seen this car. With all the oil that had been spread around both the injector trigger points and the ignition points where first replacement musts but the injectors where opening or at least getting a signal at cranking speeds although I'll admit that I never got a chance to actually test as to weather they where working when the engine was running for the short spells. I'm in agreement with a previous poster and agree that the engine was only running on the Cold Start Injector . But with a good clean up new power steering hoses and the engine management module changed it's working and is even drivable now. I've temporally replaced the engine management module with one from a 115 280 SE and while it looks the same on the outside it's totally different on the inside hopefully it has a lot more capacitance built in so it will not be as susceptible to alternator ripples in future.

About 10 years ago I escaped from working on the then new fuel injection units as I actually wanted to work on a Mini Cooper S rather than work on something easier to repair so then I knew it was time to give it all away. But other than the occasional Classic Mercedes which was first brought to me by my Uncle and then some of his friends I do not touch cars any more, but in all honestly I just love working on these old Mercedes as they where just so far ahead of their time and generally are a real pleasure to play with as I do not consider this to be work. Currently I have several of these for my own "Play Toys" but mostly they are of the twin cam variety with EFI. I find them so much easier to play with than the carburetter models.

Those along with a 408 2.2 Lt 4 cylinder fitted out as a mobile home are my current stable of "Play Toys" and I suppose I just have to add my 1982 900 SS Ducati into that group as well but I've had that since new and only run up 17,000 K on it so I do not get to play with that one much.

Col

Col:

I really truely dislike fixing butcher jobs.....!

If you've replaced the trigger points and the ECU and it runs, at least one was bad. ATF blown all other the place isn't good for wires, though -- won't bother the trigger points much, I don't think, unless it softens the rubbing blocks.

The only special tool needed to check out the ECU is an oscilliscope to see the injector pulses (and this may be avaliable on some ignition analyzers, I don't know!). Everything else can be done with a VOM. Trigger points must open and close (with no resistance closed), temperature sensors must have the correct values (I don't have that info at hand, but can get it), and the manifold air pressure sensor much have the correct reisistances on both coils AND respond to adjustments (otherwise the internal diaphrams have gone).

The ECU is very rugged.

The relays are fuel pump, master relay (operated by the keyswitch to turn the whole thing on and off), cold start valve. Fuel pump is switched by the ECU.

Check the ground for all the injectors, they all individually ground at the same spot, and check the ECU ground wire (brown) -- I've seen the ground wire go bad on one of these, causing all sorts of trouble, usually a no-start condition, but occasional stalls.

The ignition box has three wires to it, one from the points and the others trhough the ignition resistors.

Crane and Pertronix both make good aftermarket ignitions for this car, much easier than the factory, and the Pertronix can be "invisible" (that is, no extra wires, etc).

Peter

__________________
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!

But what makes this one so bad is that it is a show car and looks so good until I began digging under its skin so to speak. Previously I've only had to do normal routine maintenance but I haven't seen the car for about 18 months and since then some idiot has been mucking around with it and generally stuffing everything up.

The ECU was defiantly the problem as I've tried it in another car and it just no longer works but I'm dammed if I know what was done to it to wreck it as I've never had to replace one previously and I've even had one that was under water and all the electronics still worked. That did surprise me no end but it was only under for a few hours and it was clean water not the muddy junk that washes down the storm water drains.

Currently I've just modified the wiring harness to fit a newer Transistorized Ignition Module from one of my 116 Twin Cams along with the wiring harness for the four pins and the points lead. It even looks exactly the same unless you start digging down under the battery tray. It is only after you have removed the mounting bracket for the original one that you can see a difference and of course the trigger wire that I've had to run as the wire which is black with a white trace just no longer exists anywhere near where it should exit the loom. I'll get motivated latter and fix that one up but I've run 1,200 K's on it now without a single problem other than it is now running better than ever so I've had to muck around with the adjustments for the Auto so it actually picks up 4 th gear under 80 KPH.

The only other remaining problem is that it is loosing Power Steering fluid but there is no obvious place it is leaking from even on a hoist so I'm a bit at a loss on that count. I think I'll give it a good run and then park it on clean concrete just to see if there are any tell tale oil stains. I suppose it's a good thing that it isn't a daily driver as the owner would be missing it quite a lot by this stage.

Col

just having a read of the advice given in regards to 1973 250ce.fuel injection setup sounds the same as my recently aquired 1970 250ce.i live in darwin and the car has sat around for a long time,starting probs sound identical.have
used jumper cables so if electrics are easely demaged im f@$# for starters.knowledge is limited and i was wondering where i might find technical ,data wiring diagrams to download. any help would be appreciated,cheers

Well for the car itself without the electronics it is easy any Car Manual place will be able to supply what you need.

The D-Jet Fuel Injection system is a different story though I've yet to find one anywhere.

There are two major modules in the car one is the Ignition module which in the 114/115 series Chassis is mounted at the front of the battery carrier on a plate that bolts onto the very front and hides the Ignition Module between the front inside of the engine bay and the battery rack. The other is a big unit which is behind the kick cardboard on the left hand side of the passenger compartment just in front and below the hood release.

The ignition Module can be replaced with a kit from Jaycar and it has the same contacts so it is an easy fit no extra wiring involved and costs about $50.00 AU I was quoted by Mercedes that one was available EX Germany but they had no idea of the cost as they had not sold one for a very long time but if should be somewhere around the $3,500.00 AU + GST as you can see the Jaycar unit is the best option.

The engine management module in another story though and you have to use one from Bosch that sought of fits the car that means any 6 Cylinder unit from the wreckers will most likely work.

If the battery is dead the car WILL NOT START so replace the battery first with a known good one and go for one of the bigger ones as these things draw quite a lot of power to start. It just might cure your problem, I know it did for me on a 116 280 SE and it didn't matter that the owner had left it there because it wouldn't start for 3 years and then her son tried to pulverize it into submission by attempting to jump start it of a 24 V truck. A new battery and it worked perfectly although I would never recommend this type of thing.

There are a set of points in the side of the Distributer which quite often give you problems as well because they loose spring tension and start to float at any sought of engine speed. While a bit of a pain to change they are not expensive and are very easy to fit after you have pulled the distributer out or removed the rocker cover which will allow you access to the 2 screws which hold them in. Removing the Distributer is the easiest way to do it though.

There is another trick with these cars if they still have the black plastic bit between the fuel tank and pump at the back of the car and the tank has been emptied completely these things do not allow the fuel to flow through until you have disconnected the fuel line at the pump and let some fuel flow out.

Actually in comparison to a lot of the EFI cars that are around now these Electronics are fairly robust and can take a lot of abuse so I really would start with the simple things first and work my way back from there. The fuel filters are also another potential problem as they can clog up if you have used contaminated fuel.

I've also seen the Ignition Modules off the latter cars 116/123 fitted to these cars as well they have a coaxial points lead which just pushes into the module and another plug with 4 wires coming out of it. A cheap replacement from the wreckers but a bit harder to wire in. The only down side is the points lead is part of the points and costs around $150.00 AU it is actually very similar to the original points lead in the 250 CE but instead of ending in a 2 pole cap it is split to an earth lead and the points lead at each end.

Also always check the Cam Chain as these do wear and I have seen instances where the Iginition get so far out of timming that the car will not start. But start by removing a fuel line {I find it easiest to pull one from the cold start injector on the inlet manifold and see if any fuel flows.} If not then check that the fuel pump is actually running and pumping fuel. You can run a power lead back to these and just check that the pump actually runs and if you crack a fuel line on the output of the filter you'll be able to see if any fuel is geting through. If not have a good play around there and check that the fuel pump is actually getting fuel and that the filter has not become blocked.

Also go over every earth connection you can find pull them off the body and reconect them after cleaning both the connectors and the body. There are a whole bunch of brown wires earthed on the left hand side under the dash which can give problems. Also if tyhe fuel pump is not running check the earth as I've seen cases on other cars where these have failed and stoped the pump from running. If there is any doubt run another earth wire to a different earth point.

I hope that is of some help to you.

Col

fantastic! thanks for all the info.this gives me great confidence the old girl will live again.ill report on my progress soon as i have had the chance to weave some magic.cheers

I may be wrong, but I seem to remember seeing a wiring diagram for either the 250CE or 280E/CE W114 which showed the D-Jet ECU still with 4 outputs to the injectors as for the V8 versions. On these 6-cyl versions I seem to remember 2 of the injectors each with their own output and the other 4 injectors sharing the outher 2 outputs (in pairs like the V8). This would suggest the 6-cyl versions would still have 4 trigger points like the V8. Does my memory serve me correctly or am I imagining seeing this?

__________________
107.023: 350SLC, 3-speed auto, icon gold, parchment MBtex (sold 2012 after 29 years ownership).
107.026: 500SLC, 4-speed auto, thistle green, green velour.
124.090: 300TE, 4-speed auto, arctic white, cream-beige MBtex.
201.028: 190E 2.3 Sportline, 5-speed manual, arctic white, blue leather.
201.028: 190E 2.3, 4-speed auto, blue-black, grey MBtex.
201.034: 190E 2.3-16, 5-speed manual, blue-black, black leather.

On the 6's the injectors fire in two lots of three. If I remember correctly the V8's did it in 2 lots of 4.

I really wish I still had that Bosch book that got washed away in a flood and was impossible to replace. That was in January 1974 and I've been trying to get another copy ever since. Of course we didn't appreciate that book as it was given to us and when we wanted another one they where no longer available but it was amassing just how much it got used.

Col

V8s are 4 lots of two.

__________________
Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician

well now, having spent several hours learning about my car i have made some not so nice discoveries.plenty of testing and measuring has me convinced that the computer is at least half dead.turning on egnition,pump runs,injectors click when pressing excelerator.turning to start i may get a fire or short run.cold start injector does not come on,some argue its too warm,i think the only thing stopping it is no power at the relay when engine is cranking. injectors are not getting any power when i have run engine on hot wired cold start injector.all other probes ,sencors and and trigger points seem to function as designed.might be heading up the garden path since the info has come out of a v12 jag workshop manual.it is also bosch and physical appearance plus values stamped on items are identical to my car.
i have tried to locate another computer and have found one out of a 1973 250ce,same engine,but the last three figures of the part number are different.006 compared to mine 004.
this is where it becomes interesting again since jet another wrecker is of the opinion both are incorrect for that car and should end in 024 or 025. both cars are 114's. please someone tell me it doesnt matter and the 006 is just fine.out of a running car and well priced.
another question is the ignition.the unit under the battery doesnt hook up to anything anymore and i have normal points and coil ignition.doesnt bother me at this stage as at least i have spark.