Folks Not a Merc but the same principle. Please bear with me, I need help. I have a 3.5 V6 Petrol - SWB Mitsubishi Pajero. It had a head gasket failure. Off it went to have the Gaskets replaced along with: New Water Pump New Timing/Cam Belt New Crank Shaft Pulley (these de-laminate so need replacement). Heads refurbished - pressure tested & skimmed. All good so far. When they put the car back together, she fired up and ran for 10 minutes with no issues. She then cut out and refused all efforts to re-start. Cranking but not firing. Now she will start but is back firing and running like a dog, any attempt to give throttle results in back firing. Garage have checked and re-checked the timing - spot on. They even tried retarding and advancing it with no change. They checked all injectors - all good. Now they say that they suspect the Crank Position Sensor? Why? Well when they removed the Crank Pulley they say the blade that activates the sensor was bent and heavily marked, due to the pulley wobbling about. The thinking is that this must have damaged the CPS which has now failed. They also say that there is no other component that could cause this behaviour as it is backfiring on all cylinders, so must be getting a wrong reading or no reading from the CPS. The CPS is £120 no refundable from Mitsi. Is there anything else that could be checked?