Unusual starting with full tank - 190E 2.3

[Greg in Oz]

Recently I have noticed my 190E 2.3 behaves differently when starting from cold with a full tank of fuel. Usually, starts see the engine crank for maybe one or two seconds and then fire and idle normally. When the tank is full it now fires almost the instant the starter engages, runs for maybe less than a second then stalls. A second cranking attempt results in a normal start. Once the level in the fuel tank drops a little it reverts to normal starting behaviour on the first attempt.

I am wondering if I have a leaky injector, cold start valve or fuel distributor that is allowing a small amount of fuel to accumulate in the inlet manifold or an inlet port when the fuel level in the tank is above the level of the fuel system at the engine? This fuel could allow the engine to fire immediately when cranking before fuel reaches the inlet ports in the correct manner.

The car is running perfectly otherwise with both good performance and normal fuel consumption. It is a 1990 model with KE-Jetronic showing a little over 230,000km.

Any ideas or has anyone seen this problem before?

Thanks,
Greg