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#2
07-29-2023, 04:42 AM
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The most accurate way to adjust the point gap is the use of a dwell meter. Check in a Mercedes service manual to determine the number of degrees of dwell and using the dwell meter adjust the point gap to the specified number of degrees of dwell. As a starting point, the points can be gapped to .015 of an inch using a feeler gauge or the thickness of a common business card, The initial gap should be adjusted when the rubbing block on the points is on a high point of the distributor cam. Tighten the point hold down screws and then recheck using the dwell meter.
Last edited by WWhitmore; 07-29-2023 at 05:06 AM. 
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#3
07-29-2023, 09:18 AM
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The gap should be in the range of .012-.016" and you want to adjust toward .012" if you want the strongest spark at the plug, for performance. The narrow gap means the points spend a longer duration closed, which charges the ignition coil longer, and thus gives a hotter spark. Back in the day, Bosch points grease was put on the lobes of the distributor and the felt wiper, so that the foot of the points arm wouldn't wear out. 1 tube of grease would last a mechanic several life times. I still have my tube! Be sure to spend up, and only use Bosch distributor cap and rotor, Bosch or Beru plug wires, and make sure the coil wire is a solid core version. Make your own coil wire with bulk wire and ends that are available at places like NAPA if the wire kit comes with a carbon coil wire. Same mindset for the spark plugs. Just a standard set of Bosch or NGK. Avoid wiz-bang spark plugs like Bosch Platinums and other non-sense, unless you want to be chasing hard cold starting, misfires under load, rough idle, etc., while at the same time saying to yourself, "It can't be the spark plugs, they're new." Good luck!
__________________
 1966 W111 250SEC:
DB268 Blaugrün/electric sunroof/4 on-the-floor/4.5 V-8 rear axle
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#4
07-29-2023, 10:31 AM
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General instruction on points:
Mercedes-Benz Ponton Ignition Point Gap Adjustment and Vacuum Advance © www.mbzponton.org And remember to adjust the timing after adjusting the points: https://www.peachparts.com/shopforum/vintage-mercedes-forum/411873-m102-980-timing.html#post4159740 Last edited by rumb; 07-29-2023 at 11:02 AM.
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#5
07-29-2023, 01:49 PM
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From your previous posts you are dealing with a D-Jet engine. Is that right? If so, it likely is also equipped with an electronic switchgear (amplifier) in the ignition system. The point set for the amplified system is made with the primary lead (green wire with coax connector) as a part of the point set. The points are attached to the breaker plate with one screw, and the rubber insulator block for the green wire slips into a slot in the distributor body.
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#6
07-29-2023, 02:32 PM
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X2 on standard Bosch or NGK plugs. Don't use fancy upgrades, use the plug for which the system was designed.
__________________
"Rudeness is a weak man's imitation of strength" - Eric Hoffer
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#7
07-29-2023, 04:07 PM
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copper plugs are essential for reliability (others said that already).
The Tz box (the switch gear) has to be well grounded (firmly attached) to metal. Where it is screwed down is often sufficient. The simplest thing to clean your points with is the rough surface of a dollar bill. A good first guess at the gap for the points is the cardboard thickness of a match book (it's close, but not exact). As somebody else said, every time you mess with the point gap, you must reset the timing of the distributor over all. Lastly, while you are checking your timing at different RPMs, also check your dwell. If the dwell reading changes by more than 2-3 degrees, you have a problem that needs to be addressed. -CTH
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#8
07-29-2023, 04:07 PM
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I have worked on a lot of old cars and found the points to be the problem only twice. Once when the points had actually broken and fallen off and the other when they were carboned up.
This is easy to see and fix. The contact part of the points will have a blackened or uneven look to them. A small file, known as a points file, is just inserted between the contact points and a bit of the roughness is filed off. Points files were once (maybe fifty years ago) a common tool. I guess now the best way to find such a thing is to use a fingernail file. And should the points be checked for dwell after filing them? Of course. But only if you want your engine to run as it should. If you are just wanting it to run it should start right up. But without adjusting the dwell it will never run smoothly.
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#10
07-30-2023, 05:59 PM
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Quote:
Quote:
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#12
07-31-2023, 11:52 AM
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I posted a link to setting points above. They are the same on 99% of older cars. YES, you have to "set them up".
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#13
08-08-2023, 05:00 PM
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A small window on the distributor cap raised up and with a points adjusting tool you would turn the micro adjusting screw and watch the dwell meter until the points were correct. The one screw Frank was talking about would, in the GM version, be considered the macro adjustment. I think in the Mercedes of that era you had to just keep fiddling with the points adjustments (the one screw) and then checking the dwell until you got it right. Mercedes at least put the distributor up front where it is easy to get to.
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#14
08-08-2023, 05:43 PM
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I believe the dwell can be checked on any engine by cranking the engine with the distributor cap off and adjusting the point gap while the engine is being cranked. GM made that easy by having a window in the distributor cap which allowed the dwell to be adjusted with the engine running.
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#15
08-08-2023, 07:15 PM
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Yes, if you have a dwell meter connected!
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