My 1979 244 (K-Jetronic) about once a month refuses to start, so I crank it for up to a minute. (I've swapped electronic ignition module, coil, fuel pump relay, distributor, starter switch and cleaned and dielectric greased all connectors and chassis contacts in the engine bay, and the engine harness is OK , no rotting or abrasion. The control pressure regulator does not have a vaccuum connection). Not even a single splutter of life. But 99% of the time it runs well, irrespective of whether the tank is full or almost empty.

So when it won't start I then switch it over from gasoline to LPG (liquid petroleum gas)(dual-fuel cars are common in Australia since gasoline is very expensive)and then crank continuously for up to a minute over which time it slowly splutters into life and then runs well on LPG. Normally LPG start hot is 2 seconds and cold is 4 seconds. (My 2 year old battery can only crank for 3 minutes before its flat!). (I run my car for only 5 minutes per day on gasoline to ensure that the fuel injection system remains functional).

All I can think of is that the engine has been somehow flooded on gasoline and the one minute cranking on LPG is needed to dry out the flooded sparkplugs? My new injectors are only a couple of years old, but my fuel pressure check valve, in-tank and under body pump, thermo-time switch and its cold start injector are 30 years old. A friend suggested that the car maybe "dual-fuelling simultaneously" with the gasoline/LPG changeover relay turning on both fuels, but can a defective relay occasionally apply +12V to both the NO and NC contacts at the same time?