general information about ignition points - PeachParts Mercedes-Benz Forum

Carson357 · #1 09-23-2006, 03:02 AM

i just wanted to share something that has happened to me this past week at work, we have a customer with a 1969 280sl, he has spent literally thousands on the car to bring it to like new condition, it has a manual 4-speed which i have never seen. anyway he had it in the shop i work at many, many times(before i started there) for various issues. it has a new motor done by metric motors etc.. he has always been complaining about performance issues. so he came in upset (rightfully so), i assured him i would get to the bottom of his poor performance. the main thing i found and the reason i post this is that the coil and ballast resistor were not the correct ones for this car. his car does not have the transistorized points system, but some one had installed a coil and ballast for that system. i started by measuring the voltage at the coil with the key on engine off, he had 11v, he was complaining of very poor performance at high Rpm and going through points every 300 miles or so, this was why, too much voltage crossing the points causing them to burn. the resistor was incorrect, it was the silver resistor with a blue coil. the blue coil actually requires two resistors, a silver and a blue one, which working togeather will work for the correct application. what his car needed was red coil and red ballast resistor. moral of the story make sure you have proper coil and ballast.
before this i was thinking a coil is a coil. but this past week learned different.

wbain5280 · #2 09-23-2006, 06:08 AM

It's better to change to points to a Pertronix sensor and CD system or an optical one. Personally, I'd like an EZL but I'm going to put in an optical Crane system.

t walgamuth · #3 09-23-2006, 06:39 AM

Quote:

Originally Posted by Carson357

i just wanted to share something that has happened to me this past week at work, we have a customer with a 1969 280sl, he has spent literally thousands on the car to bring it to like new condition, it has a manual 4-speed which i have never seen. anyway he had it in the shop i work at many, many times(before i started there) for various issues. it has a new motor done by metric motors etc.. he has always been complaining about performance issues. so he came in upset (rightfully so), i assured him i would get to the bottom of his poor performance. the main thing i found and the reason i post this is that the coil and ballast resistor were not the correct ones for this car. his car does not have the transistorized points system, but some one had installed a coil and ballast for that system. i started by measuring the voltage at the coil with the key on engine off, he had 11v, he was complaining of very poor performance at high Rpm and going through points every 300 miles or so, this was why, too much voltage crossing the points causing them to burn. the resistor was incorrect, it was the silver resistor with a blue coil. the blue coil actually requires two resistors, a silver and a blue one, which working togeather will work for the correct application. what his car needed was red coil and red ballast resistor. moral of the story make sure you have proper coil and ballast.
before this i was thinking a coil is a coil. but this past week learned different.

thanks for sharing your very valuable experience. it is a problem that would be easy to have and difficult to fix.

i once had a 280e that would start up and run for a few minutes really well then gradually over five minutes get so it would barely run.

after incredible amounts of changing parts discovered the problem to be a brand new dist rotor that was a little too short.

tom w

Carson357 · #4 09-23-2006, 04:53 PM

Quote:

Originally Posted by wbain5280

It's better to change to points to a Pertronix sensor and CD system or an optical one. Personally, I'd like an EZL but I'm going to put in an optical Crane system.

the customer is a purist and wanted it all original, we have to respect his wishes.

riethoven · #5 09-23-2006, 05:58 PM

Quote:

Originally Posted by Carson357

the customer is a purist and wanted it all original, we have to respect his wishes.

I don't know if there is a torque spec. on the screw that holds the points at the specified gap, but make sure it is plenty tight because I have seen the points in Bosch distributors slip and close the gap. This was on Alfas and BMWs.

To bad he won't entertain a CDI unit because the spark is much better and there are no more points to deal with. It would also help performance.

Mark DiSilvestro · #6 09-24-2006, 12:08 AM

Also, for anyone still running points, with or without the transistor box, remember to add a tiny dab of hi-temp grease to the distributor cam, and occasionally oil those distributors that have the little oiling cup.

Happy Motoring, Mark

t walgamuth · #7 09-24-2006, 09:39 AM

also the center post of the distributor is hollow and has a felt plug. this plug should be removed occasionally and a few drops of clean oil dropped in. then put a few on the felt cap after it is placed in the hole. if this is neglected the bushings will begin to howl.

tom w

mgburg · #8 09-24-2006, 10:53 AM

Hey T:

You didn't mention a condensor (accross the point's contacts).

Didn't that system require a condensor (helps retard the erosion of the point's contact faces) or did Mercedes figure out a different way to solve that problem w/the "red coil/red ballast resistor" technique?

t walgamuth · #9 09-24-2006, 11:27 AM

all point sysetms that i am aware of use condensors.

tom w

Carson357 · #10 09-24-2006, 03:17 PM

it does have a condenser, the only mercedes that has condenser related problems is the 4.5 v-8. on those models the condenser wire has to be cut. i forgot why, but i know it will cause the engine to have ignition issues.

Matt L · #11 09-24-2006, 03:53 PM

Quote:

Originally Posted by wbain5280

It's better to change to points to a Pertronix sensor and CD system or an optical one. Personally, I'd like an EZL but I'm going to put in an optical Crane system.

I was nearly stranded twice by an optical Crane system in a H-D. Once I rode home about twenty miles on one cylinder (topping out at about 30mph). The other time I lost both cylinders, but was close enough to push it home. Crane replaced the unit after the first failure.

After the second failure, I went back to points, using the best american-made points, condensor and mechanical advance unit that I could buy.

YMMV, of course, but I'm not running another one.