Engine

IF	CHECK
Engine will not start	Wrong Engine oil viscosity. Battery has low voltage. Loose or corroded battery connections. Blown fuse(s). Cold start system not being used, or malfunctioning. Stale fuel/improper fuel/low fuel level. Dirty or Faulty Fuel Injectors. Fuel shut-off valve turned off. No fuel or improper fuel. Plugged fuel filter. Defective starter solenoid. Open-circuit in wiring.
Engine is hard to start	Check glow plug fuse. Engine is cold. Plugged fuel filter. Engine oil viscosity too heavy. Cold start system not being used, or malfunctioning. Dirty or Faulty Fuel Injectors. Loose or corroded electrical connections. Stale or improper fuel. Blown fuse.
Engine misses under load	Stale or dirty fuel. Plugged fuel filter.
Engine vapor locks	Fuel tank vent plugged. Dirt in fuel filter.
Engine runs unevenly	Loose electrical connections. Improper fuel. Stale or dirty fuel. Fuel line or fuel filter plugged. Dirty or faulty fuel injectors. Plugged air intake system.
Engine overheats	Air cleaner element missing or plugged. Defective radiator cap. Engine oil low. Engine operated too long at slow engine speed. Bleed cooling system. Check cooling fan switch. Check thermostat. Check water pump. Clean radiator screens. Check coolant level.
Engine loses power	Engine overheating. Too much oil in engine. Fuel supply being restricted. Fuel filter plugged. Fuel line pinched or kinked. Improper fuel. Air cleaner element plugged. Injection pump out of time. Dirty or faulty fuel injectors. Improper valve clearance.
Engine knocks	Low engine speed. Stale fuel. Engine overloaded. Excessively early timing of fuel injection pump.