Mercury Optimax Models 135, 150, Direct Fuel Injection., Page 143Get this manual
FUEL PUMP
Testing Fuel Pump
Install clear fuel hose(s) between fuel pump and VSTRun engine, and inspect fuel passing thru hose(s) for air bubblesIf air bubbles are found, see "Air Bubbles in Fuel Line," belowIf air bubbles are NOT found, see "Lack of Fuel Pump Pressure," below
Problem: Air Bubbles in Fuel Line
Low fuel in tankLoose fuel line connectionFuel pump fitting looseA hole or cut in fuel lineFuel Pump anchor screw(s) looseFuel Pump filter cover anchor screw looseFuel pump filter gasket worn outFuel pump gasket(s) worn outAn anti-siphon valveAir in fuel lineA dirty or clogged fuel filterThe fuel pickup in fuel tank is clogged or dirtyWorn out fuel pump diaphragmWorn out check valve(s) in fuel pumpA leaky check valve gasketPulse hole(s) pluggedHole in pulse hoseLoose pulse hoseExcessive fuel hose lengthFuel hose internal diameter too smallPrimer bulb check valve not openingExcessive fuel lift requiredFill tank with fuelCheck and tighten all connectorsTighten fittingCheck condition of all fuel lines and replace Tighten all screws evenly and securelyTighten screws securelyReplace gasketRebuild fuel pumpSee Checking for Restricted Fuel Flow" precedingSee Air Bubbles in Fuel Line", aboveClean or replace fuel filterClean or replace pickupRebuild fuel pumpRebuild fuel pumpRebuild fuel pumpRemove fuel pump and clean out holesReplace pulse hoseTighten connection(s)Cut fuel hose to proper lengthUse 516 I.Dfuel hoseReplace primer bulbFuel lift from tank to pump 48 in(1219.2 mm) maximum