1986 420 SEL - Adjusting Timing - PeachParts Mercedes-Benz Forum

#1 12-03-2002, 06:04 PM

I have a 1986 420 SEL. The timing is set at 5 degrees and it is supposed to be set at 12 degrees. How do I adjust the timing? When I turn the distributor the timing does not change. I am assuming that the computer does not allow it to be changed. Is there something I need to disconnect to adjust the static timining?

Thanks!

Benzmac · #2 12-03-2002, 07:38 PM

You can't adjust the timing on a 420. The distributor has adjustment ONLY to set up where the rotor points to the electrodes. The ignition is fired by a crankshaft sensor in the rear of the engine.

The vacuum may be missing going to the EZL...Check that first.

#3 12-03-2002, 10:02 PM

Benzmac:

I am new to this forum and it appears that I responded directly to you instead of the forum. I went to my smog mechanic yesterday and checked the state manual that all the smog mechanics use when smogging a car in CA. For the 1986 420 SEL it clearly showed 12 degrees. Starting with 1987 or 1988 it showed that the timing was non-adjustable as you described. Therefore, it appears that for the early 420 SELs the timing was adjustable. Although the car runs very clean, if I had a smog test done it would have failed becasue the timing exceeds the maximum allowable 2 to 3 degrees above or below the specs. Anyone has any suggestions?

Leon

mbdoc · #4 12-04-2002, 08:25 AM

Your SMOG guys manual IS wrong & BENZMAC is correct! The 1985 V-8s were the last ones that the timing could be changed.

You will need to reset the static distributor timing OR you might have cross-fire inside of the dist cap.

#5 12-04-2002, 10:49 AM

MBDOC:

Thanks for your response. The smog guy's book is actually the state manual used by all mechanics in CA doing smog. However, you made an interesting point. That the 1985 V8s were adjustable as far as timing. My 420 SEL was manufactured on 10/85. The factory decal in the engine compartment also does indicate the 12 degrees and refers you to the manual for adjustment. Could it be that my 420 SEL was one of the few built with adjustable timing in 1985?

Also, you mentioned that the static distributor timing may need to be re-adjusted. How do you do this?

Thanks you guys for all your help!

Leon