Hi Gang.
I am still getting the kinks out of my '85 Euro 280se (W126, M110, 5spd) and have come a LONG way. To refresh this car has only 91k, and sat for a year neglected before I purchased it. After replacing the fuel pump, accumulator, hoses, plugs, filters etc the car was completely driveable but with a hesitation and occasional miss, aqnd a strange problem that caused the car to nearly die after about an hour of driving but a quick key off and key on would make it run for another 20 minutes or so. After 20 minutes, repeat key procedure and keep driving. The car also has a light smoke from the tailpipe which I have yet to find the cause for, and fails the emmisions test here in Texas with a high hydrocarbon reading (I got it down from 1500ppm to about 600ppm by tuning the FI screw on the k-jet).

Latest changes to the car are a new exhaust from cat back (cat & O2 sensor are next) and a high performance ignition setup from Perma-Tune (This cured the key trick problem and smoothed the car ALOT!) but I still need to properly tune the k-jet on this car. The car has a diagnostic port on the drivers side wheelwell but I have found no info on the procedure to tune this car properly. Does anyone have a procedure for this??? I recall somwhere seeing that using an multimeter on 2 pins of the diagnostic port would give a voltage reading to calibrate the air / fuel mixture. Is the white plastic adjustment screw next to the distributor for idle speed or does this control the air mixture? Any an all help appreciated!

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Radioman

There isn't a single answer to your question about set-up/tuning. The problem is that you undoubtably have an aftermarket lambda control system or other systems added to meet US emissions when the car was imported.

Typical euro cars won't have any fuel control measurements at the diagnostic connector only component fault codes. Actually I'm not even sure which system the car would come with. I presume it still is plain K-jet not K-Jet w/lamda or KE-Jet. This will need to be determined to answer your question. If you get me the Bosch number for the fuel distributor I can determine this answer.

I have seen two different methods for "federalizing" these cars. One was to add a lambda system by adding a frequency valve to affect the control pressure (this was very tempermental as the control pressure has too great an effect on mixture.

The second method was even cruder. It involved a catalyst and air injection pump (a pre-lambda system for factory cars). The cars were clean enough that some tricky timing and mixture adjustments could get them through the testing. The timing was usually retarded to handle the NOX problem which made the car perform poorly. Most of these systems were deactivated somewhere along the line to get the running again.

Aside from fuel system monitoring the basic way to adjust the mixture is to use an exhaust gas analizer. If the catalyst is good then this really needs to be done in front of the cat. MB didn't make any provision for this as the factory cars either had no catalysts or they did and were monitored electrically at the diagnostic socket. The pin for monitoring is #3. If there is a connector beneath the hole the car must have come with K-Jet with lambda or KE-Jet.

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Steve Brotherton
Owner 24 bay BSC
Bosch Master, ASE master L1
26 years MB technician

Thanks for the reply!
Just went out and looked at the fuel distributor and the # is 0.438.100.069. You are correct about the fuel control box, it is a small white box laying in between the fore and aft firewalls and was made by Johnson Fuel Controls in Ca. I tried to find this company when I first bought the car and they are nowhere to be found. Even another shop that is in the same building (for 20 years) didn't remember them. The O2 sensor isna four wire unit also. Can I eliminate this box or are there other companies making such a unit? Is it possible this box is my problem??? Thanks again for the help!

Tom

Steve, did you find out anything??? I was also wrong about the O2 sensor, it is a 3 wire unit. This car has a split header that goes into a single 3" where the sensor is mounted. Then into the strangest cat I have ever seen, top mounted single 3" inlet at a 45 degree angle, with dual 2.25" outs. I just ordered the O2 sensor, new injectors, and new valve stem seals to try and get this smoking problem fixed.

Tried to install a new water pump today, and the brilliant engineers designed this motor to where you have to remove the harmonic balancer to replace the pump! Geez...

Tom

Tom,

I'm sorry that it took a while to reply. I have been severely restricted in my internet access recently for two reasons. First is Bellsouth.net's ADSL line has been useless for anything other than small file email for a week now. They claim to be replacing a router or something.

The other factor is that I am writing an article (about MB A/C) for Babcox publication's trade magazine - "Import Car". I also spent the week-end in Ft.Myers at the yearly ASA convention (I am local chapter president and state board member).

The biggest problem is that I can't get to this site at work anymore. When I offered I never dreamed that the ADSL line would be still out yesterday when I went to work.

Based upon the further info about the D.C. Johnson box, I'm sure you have a simple K-jet system with an added frequency valve dropping control pressure. Follow the line from the center/top of the fuel distributor toward the control/warm-up regulator. The regulator is under the intake manifold on the block and is impossible to see from above but the frequency valve is usually right behind the fuel distributor.

I don't know how you will solve your emissions dilemma but for diagnostic purposes (bg) I would disconnect the electrical to the frequency valve (removal is not necessary unless its leaking) and readjust the mixture.

Once disconnected the mixture will be too lean if the system had been set up properly. If you have further questions about this email me as I won't see this if the ADSL link is still screwed-up but I will get my email at the shop. We installed about ten of the D.C. Johnson controllers in the mid eigthies on casrs we imported and federalized.

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Steve Brotherton
Owner 24 bay BSC
Bosch Master, ASE master L1
26 years MB technician

Just a note. I'm pretty sure the 1985 Euro car originally has KE-Jetronic (probably without O2/lambda). At least, all Eurocars I know from this period has.

That distributor 0 438 100 069 is a simple K-jet.

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Steve Brotherton
Owner 24 bay BSC
Bosch Master, ASE master L1
26 years MB technician