407914-2030 ZEXEL CONTROL UNIT Cross 4079142030

Possible Causes/Corrections
Air or Water in Fuel System/With air in the fuel system, the engine will normally be difficult to start, run rough and release a large amount of white smoke. If the engine will not start, loosen a fuel injection line nut and crank the engine until fuel comes out. Tighten the fuel line nut. Start the engine. If the engine does not run smooth or releases a large amount of white smoke, loosen the fuel line nuts one at a time until the fuel that comes out is free of air. Tighten the fuel lines nuts. If the air can not be removed in this way, put 35 kPa (5 psi) of air pressure to the fuel tank.
Do not use more than 55 kPa (8 psi) of air pressure in the fuel tank or damage to the tank may result.
Check for leaks at the connections between the fuel tank and the fuel transfer pump. If leaks are found, tighten the connections or replace the lines. If there are no visual leaks, remove the fuel supply line from the tank and connect it to an outside fuel supply. If this corrects the problem, the suction line (standpipe) inside the fuel tank has a leak.Water in the fuel can cause rough running and possible fuel system damage. Valve Adjustment Not Correct/Check and make necessary adjustments as in Testing and Adjusting section of this Service Manual. Intake valve clearance is 0.38 mm (.015 in.) and exhaust valve clearance is 0.64 mm (.025 in.). Also check for a bent or broken push rod. Bad Fuel Nozzle(s)/Find a bad nozzle by running engine at the rpm where it runs rough. Loosen the fuel line nut enough to stop fuel supply to that cylinder. Each cylinder must be checked this way. If a cylinder is found where loosening of the nut makes no difference in the rough running, test the nozzle for that cylinder. To test a nozzle, remove the nozzle from the engine and test as in Testing and Adjusting section of this Service Manual. Fuel Leakage From Fuel Injection Line Nut/Tighten nut to 40 7 N m (30 5 lb. ft.). Again check for leakage. Bad Fuel Injection Pump/An injection pump can have a good fuel flow coming from it but cause rough running because of slow timing that is caused by wear on the bottom end of the plunger. See the Testing and Adjusting section in this Service Manual for the correct specifications and procedure to check the plungers and lifters.Fuel pumps which are severely scored from debris can cause rough running, but fuel dilution usually occurs before horsepower is affected.Low installation torque on the fuel pump retaining nut can cause misfire, rough running and low power. Fuel Has a High "Cloud Point"/In cold weather operation this condition should be checked first. The fuel "cloud point" is the temperature at which wax begins to form in the fuel. If the atmospheric temperature is lower than the "cloud point"