Bosch D-Jetronic Fuel injection 1974 280 SE W116

[Jimb]

Hello again from Jim(Jimb).
My car is running fine no problems ,the motor is very sweet no oil leaks etc.
To many this may appear to be a ridicules post. Should I be worried about the complexity of this early electronic system in the terms of reliability? Should I just drive and enjoy this car instead of finding things to worry about? By trade I was an electronic tech covering many areas over my working life. I guess I am concerned if I took it on a long trip the fuel injection could fail. I have no idea where all the bits are and the diagnostic process . I believe the later system was less complex. Can it be converted to the later system if need be?
It would be unheard of to even suggest converting it to the standard non injected form, I suppose the cylinder head as well as the intake manifold would need to replaced and cost wise to achieve less performance but greater reliability would be out of the question. The electronics would be the old style discreet components with non of the nasty surface mount and large scale intergration stuff,so it should be fixable however I suspect this part is reliable it is the other stuff that I do not understand that is likely to be the scary stuff. Any thoughts on this? Regards Jim

 

[c107]

Hello again from Jim(Jimb).
My car is running fine no problems ,the motor is very sweet no oil leaks etc.
To many this may appear to be a ridicules post. Should I be worried about the complexity of this early electronic system in the terms of reliability? Should I just drive and enjoy this car instead of finding things to worry about? By trade I was an electronic tech covering many areas over my working life. I guess I am concerned if I took it on a long trip the fuel injection could fail. I have no idea where all the bits are and the diagnostic process . I believe the later system was less complex. Can it be converted to the later system if need be?
It would be unheard of to even suggest converting it to the standard non injected form, I suppose the cylinder head as well as the intake manifold would need to replaced and cost wise to achieve less performance but greater reliability would be out of the question. The electronics would be the old style discreet components with non of the nasty surface mount and large scale intergration stuff,so it should be fixable however I suspect this part is reliable it is the other stuff that I do not understand that is likely to be the scary stuff. Any thoughts on this? Regards Jim

There are still plenty of cars getting around with D-Jet so it can be reliable. Often problems are caused by mechanics who don't know the system than any fundamental problems with it. The main problem I have heard is that the rubber fuel hoses in the engine bay get old, leak and cause engine fires. Some parts like injectors are expensive too.

personally if it was my car I would check the fuel hoses and then just drive it.

 

[SEL_69L]

When the D-Jetronic electronic fuel injection was first introduced, there were very few old schools mechanics who fully understood how it worked.

Bosch took a step backwards, and introduced the K- Jetronic semi mechanical system, because of the lack of experience / knowledge or expense problems that the D-Jetronic system suffered from.

In actual fact the D Jetronic system, when properly maintained, is reasonably reliable, and more so these days when it is supported my more modern trained support personnel. These days, D-Jetronic is much better understood.

I guess with your electronic tech background, you may be able to appreciate the D -jetronic system more than most.
if you spend a lot of time doing Google searches on the D-Jetronic system, you should be able to appreciate all of the maintenance problems (or lack of), then go looking or anticipating problems.

Knowledge is your defence, but continue to enjoy your car.

 

[Jimb]

Hello Bryce and SEL69L.
Thank you for your replys. I did have a look at the hoses a couple of weeks back and could not see anything too terrible however I think as you have suggested they should be replaced in the near future. I think maybe I should invest in a fire extinguisher. I believe they are supposed to have one. Definitely not under drivers seat have not looked under passenger seat..However having said that I think it would be safer to get away from it. It will be getting a new windscreen rubber and some panel repair work very shortly.
Kind regards Jim.

 

[c107]

The D-Jet 350SL at about 3:20 in this video is a victim of a fire as described above:

 

[Jimb]

Hello Bryce.
I have ordered the injector kits from Thomas Hanson should have them next week.
I am not looking forward to doing the job. I may feel better about it when I have the bits and I can get a better idea of what is involved. I feel I need to hasten slowly with this car. This injection system absolutely scares me. I am not in a financial position to throw money at it.
In my younger days I just got stuck into what needed to be done and never thought about it. As I have advanced in age I have lost a lot of confidence in myself.
Kind regards Jim.

 

[c107]

Understand the trepidation with D-Jet. Good thing is there are a lot of resources on the net for this system, and it wasn't exclusively used by mercedes, other european brands like Citroen used it too, bringing up the pool of knowledge.

while your car might have a more complex system than the later ones, the M110 thrives on the higher compression that your earlier engine has.

 

[Jimb]

Thanks Bryce.
I have found a local guy who served his time on these I may get a quote from him he has all the stuff to clean the injectors as well. I know another owner that had a fuel problem with his and he quickly diagnosed it to be the fuel pressure regulator and he fixed it at reasonable cost. He loves these cars and reckons they are bullet proof and I should not be concerned about it. He said he would show me what all the bits and pieces are so at the least I will get a quote when the kits arrive..
Kind regards Jim.

 

[Oversize]

DJet would be far easier to convert to modern EFI than the later Kjet, plus the inlet manifold actually flows better. If it dies go a modern ECU with some updated sensors & new wiring & you’ll have a far more efficient & reliable unit. I’d even replace the dizzy with coil packs to avoid trigger issues.

Oh and best advice is to never drive an old car without a fire extinguisher & a sound insurance policy.

 

[Jimb]

Hi again Mark.
you have made some interesting comments here. I will invest in a fire extinguisher and I think it might be handy to have a spare pair of underpants handy in case the extinguisher is insufficient !. I like your idea of the EFI stuff . would something from the wreckers of say a Falcon or Holden be suitable ? Finding a suitable distributor may present problems. Has anyone out there actually done this. The car is away at the moment having some body repairs, the windscreen rubber needed replacing and unfortutley someone had glued the windscreen In with expoxy bond where it was leaking and the screen broke getting it out so this has delayed me getting the car back. I only got this car at Easter time .I am yet to look under the distributer cap .I will need to read up on the trigger points adjusting procedure .I am hoping these points only carry a small amount of current and are not prone to pitting and burning. my every day drive is the 1969 Hillman Hunter so this might give you some idea why I find this stuff scary .I fitted a hall effect sensor kit in it's distributer to eliminate the points .
Kind regards Jim .

 

[Jimb]

I was not thinking straight when I made a comment on a suitable distributer.
the coil packs would remove the need for the distributer I would think. Just a nice blanking plate over the hole .I am warming to the idea.
Regards Jim.

 

[Oversize]

It means you have far greater control, more advance & no moving parts to wear out. Win win! Aftermarket ECU & coil packs the largest expense...

 

[Styria]

Thanks Bryce.
I have found a local guy who served his time on these I may get a quote from him he has all the stuff to clean the injectors as well. I know another owner that had a fuel problem with his and he quickly diagnosed it to be the fuel pressure regulator and he fixed it at reasonable cost. He loves these cars and reckons they are bullet proof and I should not be concerned about it. He said he would show me what all the bits and pieces are so at the least I will get a quote when the kits arrive..
Kind regards Jim.

Hi Jim, this person may well be your best friend yet. Lots of guys familiar with the older Benzes have either retired, or even kicked the can. I can't really comment on Mark's suggestion - the cost of the required parts for any conversion to a more modern system may be beyond what you may be prepared to spend. Regards. Styria

 

[Jimb]

Hi Styria.
You may well be right. I will see how it pans out when I get the car back from the panel beater. I could be worrying needlessly, there just seems to be so many bits and pieces to go wrong.
Regards Jim.

 

[Oversize]

Apparently these are good value for money (I haven’t used them myself):

https://www.linkecu.com/

 

[Oversize]

And of course there’s Mike but not sure what he can supply for D Jet. If nothing else he can provide great advice:

https://dkubus.com/

 

[Helmet]

D jet is easy to repair and maintain if you can get parts at reasonable cost. This seems to be the issue these days.

 

[Jimb]

Hello Mark.
Had a bit of a look could not get any idea on pricing.
Regards Jim