A friend owns a 1966 Mercedes Benz 230SL. He brought it over last night as it was running very rough. I pulled off the distributor cap and looked at the points and rotor. I cleaned the rotor and lightly sanded the contacts. The manual indicated the points gap was about .015". I bumped the starter to get the points rider on top of one of the lobes. The point gap measured about .008". I readjusted the gap to .015". Put everything back together but it seemed to run worse.

I hooked up my timing light (inductive type) to check to see if each spark plug was firing. At idle, my light didn't fire on 2 of 6 plugs unless we stepped on the gas slightly to increase the idle. Then they all fired.

I had him put some gas dri in the tank to see if it was moisture related. He was able to drive it home but could never get it past about 50 mph.

How could the car run with the point gap off so much? He has no idea when the last tuneup was. Would the first steps be to change out the following - points, rotor, cap, condenser, coil, plugs and plug wires?

If not what would be your recommendations?

As not to waste time time and know where you are, take a compression test first.
Then , before spending $ on points/cond, I would recommend converting it to electronic ign. Short $$ and a big improvement.
I like the Crane units. The idea is get rid of the points.
These are mechanical FI cars and can not be made to run well without dead on ignition. [ no feed-back between the systems].
From there you can go down the line with diagnosis, [ wires, plugs, fuel, etc], but that is a good start and the weak link in the ignition system.

Adjusting the points gap is a crude way of getting the dwell right. It may be that the 'correct' gap gives an incorrect dwell on a worn dizzie.

The poor spark might also be related to wear, or could be the usual causes of wires, plugs etc.

Depending on the type of electronic conversion, this may stop the wear affecting the dwell angle, but in extreme cases the spindle jigging about will affect the HT as the rotor moves around relative to the cap.

Opps....
Forgot 'bout the worn Dizzie....

I like that one ... gonna use it, if ya don't mind....

Neil,

I can obviuosly confirm the dwell with a dwell tach. Would a first course of examination be to set the points to give the desired dwell regardless of whether the gap matches the factory setting or not?

Mike Morehouse

Yes and no! Use the dwell tach to get the dwell right. If this results in a gap that is well away from the factory setting, then something is wrong, probably excessive wear in the bearings of the dizzie. If the wear is this bad, its never going to work well.