OPERATION N° D.IE 144-0: Checking the electronic fuel injection system. ( CITROEN 1494 Tester ) WARNING : Certain actions must be avoided at ail costs as they would damage the components of the electronic fuel in- system, in particular the electronic control unit : 1) Never use a rapid charger, and never carry out arc or spot welding on the car chassis without first having disconnected BOTH battery leads and isolated the « + » earth lead.