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Bosch D Jetronic and K Jetronic Troubleshooting

374K views 116 replies 43 participants last post by  ianrandom 
#1 ·
#63 ·
You were right, I plugged in the 0280002008 ECU and the car runs fine now. The only difference was the case did not have the little pins with the rubber mounting feet that my ECU had. A couple of well placed zip ties took care of that problem.

Thanks for the help,

Smitty
 
#66 ·
M116 D-Jetronic

Hi

I have a Mercedes M116 3.5L D-Jetronic

It just goes on 3 cylinder on one side and 1 on the other side. it has spark and getting fuel to the cylinders that have problems. trigger connectors are switching and distribution system has been changed. has also changed pressure sensor with no improvement.

any good suggestions? :surrender:

best regards

Benz racing Norway
 
#67 ·
Hi

I have a Mercedes M116 3.5L D-Jetronic

It just goes on 3 cylinder on one side and 1 on the other side. it has spark and getting fuel to the cylinders that have problems. trigger connectors are switching and distribution system has been changed. has also changed pressure sensor with no improvement.

any good suggestions? :surrender:

best regards

Benz racing Norway

Sorry, running on 4 cylinders and not 3 as I wrote
 
#70 ·
Hi Nutz,

Im in the process of sorting a few issues with my 1977 W116 450SE (M117) and the next stage is removal of the LPG (Propane) fuel system that came with the car to return it to running on petrol only.

The only issue now stopping me from removing the LPG system is that the car wont start on fuel or run under 2000 Rpm, drop the revs below 2000 and the car shuts off, no stumbling, coughing or roughness but she just stops cold.

You cant even "Catch" it with the throttle.

On LPG the car idle is all over the place and the car is much smoother on petrol just nothing under 2000.

Any help appreciated.

Tony
 
#71 ·
I have an 82 W126 380SE RHD model in south africa. Car has stood without being used for approx 2 years. tried starting the car wouldn't take at all, then found fuel pump to be defective. Replaced fuel pump and high pressure filter, engine now starts easily runs for couple of seconds presumably off the cold start injector, then cuts out. If I wedge a small object in the air mass sensor plate to keep it open engine continues to run. Air mass sensor plate does seem a little stiff but does move up and down when depressed. Is this a likely cause of the problem, and what do I do to rectify the problem as I am a bit reluctant to start opening up the fuel distributor unless absolutely necessary.
Duncan
 
#73 ·
Djet on a 75 350SE

Dear Nuts 4

I've been trying to run down a low power issue. Found that the temperature switch goes to ground when hot. I've ordered a new one. Now I've got a question. The change-over works when the AC is turned on but not when I ground the temp. sensor. My Haynes book shows release contact connection, should this be check there?

Thanks
 
#74 ·
I'm a new W116 owner here in Canada. I have a 1979 450 SEL with the 4.5 motor. I'm having some trouble with what I think might be a fuel starvation issue.

The car will start with difficulty both cold or warm. On cold start it idles very rough and I need to manually keep the airflow plate open a little bit. After it warms up to operating temperature the rough idle disappears but I still need to manually keep the airflow plate open slightly.

Both hot or cold when I touch the gas pedal even a little the engine stumbles and then dies. It will not develop any RPM above an idle. It will restart again with diffculty but does the same thing everytime I press the gas.

I have checked fuel delivery to the fuel distributor and there is no problem with the fuel getting that far. I have cleaned the inlet fitting screen and it does not restrict fuel flow either.

I'm not familiar with the K Jetronic system so if anyone has idea what the problem might be, I would really appreciate the assistance.


Thanks,

Roy
 
#78 ·
W114.072 D-Jet ICU

Hi Nutz,
Do you happen to know or know where I can find some way to troubleshoot the components in my ICU. I have it out of the car since the previous owner had bypassed it. It runs rich and high idle and I need to try to get back to correct setup before I troubleshoot why it is running like this.


Thanks
Tim
 
#79 ·
Points primary 1.2 - 1.6 Ohms secondary 7 - 12K Ohms

Transistorized ignition with starting resistance primary 0.33 - 0.46 Ohms secondary 7 - 12K Ohms

Transistorized ignition without starting resistance primary 0.5 - 0.9 Ohms secondary 6 -16K Ohms


With starting resistance
Turn key to on position

Connect a voltmeter to the coil #15 terminal and ground. You should get about 4.5 V.
Now, #1 of coil to ground, you should get 0.5 - 2.0 V, and if any higher, the ICU needs replacing


Without starting resistance

Unscrew diagnostic socket cap.
Turn key to on position

Connect a voltmeter to terminals 4 and 5 and you should get 0 V. If you get anything higher than 0.1 V, turn the ignition switch off immediately. The ICU is toast. Best to have a friend at the ready sitting in car.

Curious, is your control lead going to distributor very stiff?
 
#80 ·
Thank You for the reply, The control lead going to the coil was not bypassed. The leads that go everywhere from the ICU are bypassed. I have the ICU out of the car and the car is running. It is just not quite proper at the moment. It is running rich and very high idle when timed correctly. I was going to troubleshoot the internal components of the ICU but I cannot find a schematic for it. I am hopinh to find an obvious component that is bad if not I will be forced to purchase a whole unit.
 
#82 ·
Ok, I will have to check that out. That lead was not connected. There was only a wire direct from the distributor to the coil. Someone had removed all the wiring from the ballast resistors and the ICU. I have not been able to find an electrical schematic for the ICU to be able to tell if it works out of the car yet. I have the equipment to test the componnents but not knowing what each one is exactly has stopped me. With all of my searching at this point I think I am going to try to re attach everything the way it belongs and replace the temp sensors on the head, try to figure out if there are other sensors I need to replace and where they are located. set and tune everything after that then see if I need an MPS. It has been an uphill battle for me considering finding the information on this Euro version car has been a fight every time. It has been a huge learning curve with the D-jet. My search now includes the temp sensor with the two round prongs. It is a VDO sensor and I cannot figure out the proper part number so I can order one. Both of the sensors that are not the level sensor have flakey readings with an ohm meter. I have tracked down the Bosch one but not the VDO one.
 
#83 ·
Nutz, forgive me I had missed some of your post. This ICU may still be good and I will rewire everything and test the way you have suggested. I will look into fixing the board in it if these tests do not pass. I have the in car schemtic so I can rplace the missing wires and reattach the ones that are flying to their correct position.
 
#85 ·
Yeah I have tried that :) it does seem to run a little leaner. The problem is my idle is still way to high. I need to troubleshoot my MPS and throttle position sensor to figure out the idle issue. I was in that process today but I also have 15 mature hardwoods in my yard and the first dry day I have been home this fall so it was 12 hours of that today instead of playing car today.
 
#87 ·
I have not tweaked with anything. I will add clamps to the hose. I have made sure it is a good condition hose. I have not checked the CO adjustment. I have actually just learned today that there may be a CO adjustment. I am looking into purchasing a CO meter if I ever get to the point of having to check that.
 
#89 ·
When I received the car it had teh set screw for the linkage set all the way down. I have not tried adjusting anything. I did find that the flap in the intake was not resting straight up and down and was actually turning past where it should be resting and was sticking. This has not affected the idle speed. I really need to get a vaccum tester but I have replaced all but two vacuum lines that appear to be in good shape. I am honestly thinking that I am experiencing a vacuum leak but only through the MPS. I did have very high idle before my vacuum line replacements and it has gotten better. Just not correct. Now discussing with you more on this I beleive for my idle I really need to replace the MPS. I know if you pinch off the hose going to the intake from the mps I can almost stall it at idle. I had forgooten this piece of troubleshooting with all the other things I have been working on.
 
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