Gruss aus Schweden (MB W116 450 SEL '74)

Hello,
Thank you for the membership for this site and forum!

I have owned my MB 450 SEL (1974) since 1999.
It's exterior is painted black (040) with an olive green velour interior (966).
The car was registered in Sweden in January 1974 so it is build late 1973.

I have been driving her summertime mostly (April to September) and I added about 33.000 km in the last 25 years.

The car is in a very original state. It has been a company car from 1974 to 1996. I do think that they had a chauffeur for the car as well (at least in the early years).
There are some signs of modernities like for instance the remains of a NMT car telephone installation (mid/late 80's). This system is not available anymore since many, many years.
 

Last year I have had more and more trouble with the engine not running very well. I did replace all the plugs with NGK BP6ES summer 2024 and that was quite an improvement (not having changed plugs in 20+ yrs).
But in spring this year the motor was hesitating and stuttering and things got only worse.
At first I was thinking about the ignition system (moist) and inspected and cleaned the cap and rotor. But that made no big difference. So after checking all connections, my son suggested to buy some starting gas to rule out either fuel delivery or ignition system.
Well with starting gas sprayed straight into the inlet on the air flap (air cleaner removed) the car did run and not bad either.

So this turned out to be a fuel delivery system problem (has not been a problem in 25 yrs). The pump is priming during starting, you can hear it whine 1-2 seconds when turning the key.
I removed the distributor assembly again and took out the trigger points mechanism. That did not look so good. Obvious wear of the cams, probably due to insufficient grease on lobes.
While cleaning the cam shaft with acetone I noticed some surface corrosion on the lobes. That is not optimal for keeping friction low of course.
So I bought a tube of Bosch Zündkontakt Fett Ft1v4 (45 ml) and smeared a thin layer of that around the cam axle lobes. My felt parts are really worn as well (almost to the metal). I also tested continuity to ground for all four trigger points and no.3 was not connecting (this is with the triggerpoint mechanism alone on a bench with multimeter). So I cleaned all trigger points with Electronic ceaner. I did not dare use brake cleaner, because of the nice plastic covers over the trigger points. Now all 4 points showed continuity to ground.

Re-assembled and re-installed the distributor: no good. Car engine now only runs on starter valve, about 3-5 seconds and then dies. Car runs rough with starting gas applied, worse than before.
When I checked the pins in trigger points connector (rectangular with 2 + 3 pins: 1-2-3-4-5(empty)-6, of which no. 2 is ground) pin no. 3 never showed continuity to ground. But while testing small revolutions I had continuity to ground in different combinations:
pin1 alone,
pin4 alone,
pin1 and 4 together,
pin1 and 6 together
and pin 1, 4 and 6 together (not in this particular order, just the combinations I could find).
This doesn't seem right regarding the fact that the injectors should fire in pairs, evenly distributed over one rotation of the shaft.
However I haven't done the test that will show when exactly which trigger point will make contact to ground and at which angle of the distributor shaft and for how long. That will be my next test and I would like to find some help here.

Best regards, Arman

Hi Arman,

when you see rust on the shaft itself, you need to remove it. Otherwise it will be like sandpaper on trigger cams. If they are down too much, we have replacement cams.

Anyhow welcome with your director's car in Jetronic.org !

Hello Volker, thanks for your advice.
Really disappointing to find surface rust on the distributor cam shaft lobes. I think that might have accelerated the wear on the trigger points cams.
I have been looking for a replacement for trigger points mechanism, but you suggest that the cam shaft should be replaced and the trigger cams can be sourced at jetronic.org?
Is it hard to find a used or new distributor shaft in good shape?
Or should I buy a used distributor body with a good cam shaft (300-600€)?
Best regards,
Arman

Hi Arman,
in the past some guys here tried to polish the rust away.
Some were succcessful, some were not. Maybe only some little 'pitting' remains, maybe there are scars that cannot be treated without special equipment.
I think, best is to try to polish the rust away at first.
If this fails, you need another distributor.
If the trigger cams are not totally worn,they can be readjusted using my tool you find in the compendium.

Regards
Norbert

Hello Norbert and thank you for your advice as well!
I will start a new topic for my distributor shaft and trigger points cam issues.
I have some more explaining pictures to share.
Best regards, Arman