BenzWorld Junior Member
Date registered: Apr 2012
Vehicle: 1970 Mercedes Benz 250
Mentioned: 0 Post(s)
Quoted: 4 Post(s)
OK finally PROGRESS! FIXED!!! Running beautiful!!
So, I changed the plug wires because radiotek brought up the resistor and non resistor wires... NO CHANGE in misfiring... However I wanted all the wires to be non resistor since the NGK plugs I used had resistors in them.
I also chalked up the plugs to needing a tune up any way and it def had more pep OFF idle(2nd stage on the carbs)
So I kept looking at the points on the distributor but they looked fine...... The auto parts store guy, Bryan had said you have to take them out to really look at them... so I did... I cleaned them with a dremel with a wire brush attachment... and I noticed the points were touching each other on a angle and were not mating perfectly flat. So i decided to bend the arm Just a tad to get the mating surfaces to be even.... I knew that even on angle it wouldnt matter much as long as they made contact....
However, when i put them back in I decided to adjust the points so they were touching the cam on the distributor... I noticed when I took the points out the screw marking was in the furthest out position.. when I adjusted it the screw wear marks were about 1-2mm off.
I went to start the car and PERFECTO! Finally running on all 6....
I adjusted the idle air screw adjustments (1.5 turns out) and took it for a ride.... NOW it was detonating if I was anywhere past 1/4 throttle... I went back tot he auto parts store and bought the only set of points they had in the store... FUNNY THING, the points were $7 the wires were $20 and the plugs were $20.. like i said though I chalked that up to running better and all the same wires... I bought the points but did not install them I have them as a spare in case I run into this issue again.
So now im detonating... What did I do? I adjusted the timing, first time detonation was worse(i think i advanced it too much) and more detonation. second time I retarded it and sure enough all detonation is gone and the car is running beautiful....
SO My summation about the idle issues with these cars is check the points adjustment first, bend the arm if they dont contact flat and make sure they are close to touching the distributor otherwise the cam will not interupt the coil from firing....
I know people claim the carbs are nightmares however I could see how the points could really screw someone up...
my car would run on 3 cylinders then after cleaning up the corrosion would run on 5 and It was driving me nuts... I think to even a mechanic with experience, checking the spark on all cylinders multiple times, it is of major importance before tinkering anywhere else.... I thought it was the coil at one point but I could not understand how it would spark for some and not others.. and then spark on the ones that weren't firing intermitentl