Fuel tank debris. It amazes me how much crud is in fuel and the tanks it is stored in. It also amazes me how many cars out there have the filter at the furthest end of the fuel line, (talking about the 500, not sure of the 126`s) , in the engine bay of all places, where theres a capsule of fuel being heated up.
If the filter is put as close to the outlet hose as possible, ie next to the tank, that will avoid any debris resting in the fuel line, before reaching the pump, clogging up the fuel delivery.
Having had a new fuel filter just by the tank, (on my 500), and knowing my tank is a very clean one, it can be said that the quality of fuel beneath the garage forecourts ar less than clean, that after a year my filter has plenty of debris in it .
That is of course your cutting out is due to fuel. Hope you find the problem. Mike.