Spark wires and coil replaced; W108 still wont stay cranked

[cnm]

My 1968 W108 wasnt staying cranked when stopped. The only way to keep it cranked at stop lights was to put it in neutral and give it a little gas. I had the spark wires and coil replaced. This solved the problem ... for two weeks.

Now the problem has re-emerged. Any thoughts? I am not sure the last time the spark plugs were replaced but they look pretty good (see below).

[Edward Wyatt]

Is it a 280S or SE? Your curb idle speed might be a little low, mixture might be a little lean. Hard to tell without more info.

I like to use NGK plugs on the old timers, the threads don't gall and they don't foul out like the others, fwiw.

Before you touch the fuel system, I would make sure you have the ignition system up to snuff, including a new cap and rotor. A Valve adjustment wouldn't hurt either. Make sure you use a quality set of copper cored ignition wires, that is what these cars were designed to use.

From the picture, it looks like it might be running a little lean. Check for vacuum leaks or perhaps the wrong heat range plugs were used.

[Jub]

Did you check for a vacuum leak (check all hoses going from distributor to carb). Also, check to see that the seal from you manifolds to carb doesn't have a leak (each carb is held on by 4 bolt-may want to tighten these in case they have become loose).